HARDENED OPTICAL WINDOWS WITH ANTI-REFLECTIVE FILMS HAVING LOW VISIBLE REFLECTANCE AND TRANSMISSION FOR INFRARED SENSING SYSTEMS

PRIORITY

[0001] This application claims the benefit of priority under 35 U.S.C. § 120 of U.S. Application Serial No. 63/257814 filed on October 20, 2021, and 63/344147 filed on May 20, 2022, and 63/410320 filed on September 27, 2022, each of which is incorporated by reference herein in its entirety.

BACKGROUND

[0002] Light detection and ranging (“LIDAR”) systems include an electromagnetic radiation emitter and a sensor. The electromagnetic radiation emitter emits an electromagnetic radiation emitter beam, which may reflect off an object, and the sensor detects the reflected electromagnetic radiation emitter beam. The electromagnetic radiation emitter beams are pulsed or otherwise distributed across a radial range to detect objects across a field of view. Information about the object can be deciphered from the properties of the detected reflected electromagnetic radiation emitter beam. Distance of the object from the electromagnetic radiation emitter beam can be determined from the time of flight from emission of the electromagnetic radiation emitter beam to detection of the reflected electromagnetic radiation emitter beam. If the object is moving, path and velocity of the object can be determined from shifts in radial position of the emitted electromagnetic radiation emitter beam being reflected and detected as a function of time, as well as from Doppler frequency measurements.

[0003] LIDAR systems in automobiles, and other infrared sensing systems in exposed environments, such as aerospace or home security applications, need to be protected from the environment and various sources of damage, for example, with a covering lens or cover glass window. Vehicles are another potential application for LIDAR systems, with the LIDAR systems providing spatial mapping capability to enable assisted, semi -autonomous, or fully autonomous driving. In such applications, the electromagnetic radiation emitter and sensor are mounted on the roof of the vehicle or on a low forward portion of the vehicle. Electromagnetic radiation emitters emitting electromagnetic radiation having a wavelength outside the range of visible light, such as at 905nm or 1550nm are considered for vehicle LIDAR applications. To protect the electromagnetic radiation emitter and sensor from impact from rocks and other objects, a window is placed between the electromagnetic radiation emitter and sensor, and the external environment in the line of sight of the electromagnetic radiation emitter and sensor. A window is similarly placed between the electromagnetic radiation emitter/sensor and the external environment for other applications of the LIDAR system, such as aerospace and home security applications. However, there is a problem in that rocks and other obj ects impacting the window scratch and cause other types of damage to the window, which cause the window to scatter the emitted and reflected electromagnetic radiation emitter beams, thus impairing the effectiveness of the LIDAR system.

SUMMARY

[0004] The present disclosure solves that problem with a window that includes first and second layered films. The first layered film may face away from an electromagnetic radiation emitter/sensor when installed in a LIDAR system and include a scratch resistant layer embedded therein to provide damage resistance to the window. Thus, rocks and other objects impacting the window are less likely to cause defects to the window that scatter the emitted and reflected electromagnetic radiation from the LIDAR sensor, resulting in improved performance. In addition, the first and second layered films further include alternating layers of materials having different indices of refraction (including the material providing the hardness and scratch resistance), such that the number of alternating layers and their thicknesses can be configured so that the window has high transmissivity and low reflection in a desired wavelength range (e.g., over a 50 nm wavelength range between 1400 nm and 1600 nm). The alternating layers of material may be further selected such that the window transmits and reflects relatively low amounts of radiation in the visible spectrum, thereby providing the window with aesthetically pleasing dark appearance while diminishing signal noise caused by visible light that may otherwise impinge on a detector of a LIDAR system.

[0005] According to an embodiment of the present disclosure, a window for a sensing system comprising a substrate comprising a first surface and a second surface, the first surface and the second surface being primary surfaces of the substrate. The window includes a first layered film disposed on the first surface of the substrate, the first layered film comprising alternating layers of one or more higher refractive index materials and one or more lower refractive index materials, wherein refractive indices of the one or more higher refractive index materials of the first layered film are higher than refractive indices of the one or more lower refractive index materials of the first layered film. The window includes a second layered film disposed on the second surface of the substrate, the second layered film comprising alternating layers of one or more higher refractive index materials and one or more lower refractive index materials, wherein refractive indices of the one or more higher refractive index materials of the second layered film are higher than refractive indices of the one or more lower refractive index materials of the second layered film. The window comprises a maximum hardness, measured at the first layered film and by the Berkovich Indenter Hardness Test, of at least 8 GPa, The quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films are configured so that the window has: an average percentage transmittance, calculated over a 50 nm wavelength range of interest between 1400 nm and 1600 nm, of greater than 90% for light incident on the first surface and the second surface at angles of incidence of less than or equal to 15°; an average reflectance, calculated over a 50 nm wavelength range of interest between 1400 nm and 1600 nm, of less than 1% for light incident on the first surface and the second surface at angles of less than or equal to 15°; and an average percentage transmission, calculated from 400 nm to 700 nm, of less an 5% for light incident on the first surface and the second surface at angles of incidence of less than or equal to 15°.

[0006] According to another embodiment of the present disclosure, a window for a sensing system includes a substrate comprising a first surface and a second surface, the first surface and the second surface being primary surfaces of the substrate. The window also includes a first layered film disposed on the first surface of the substrate, the first layered film comprising alternating layers of one or more higher refractive index materials and one or more lower refractive index materials, wherein refractive indices of the one or more higher refractive index materials of the first layered film are higher than refractive indices of the one or more lower refractive index materials of the first layered film. The window also includes a second layered film disposed on the second surface of the substrate, the second layered film comprising alternating layers of one or more higher refractive index materials and one or more lower refractive index materials, wherein refractive indices of the one or more higher refractive index materials of the second layered film are higher than refractive indices of the one or more lower refractive index materials of the second layered film. The window exhibits a maximum hardness, measured at the first layered film and by the Berkovich Indenter Hardness Test, of at least 8 GPa. The quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films are configured so that the window has: an average reflectance, calculated over a 50 nm wavelength range of interest between 1400 nm and 1600 nm, of less than 0.5% for light incident on the first surface and the second surface at angles of less than or equal to 15°; a CIELAB L* value of less than or equal to 45 for angles of incidence of less than or equal to 60° on the first layered film; and CIELAB a* and b* values of greater than or equal to -6.0 and less than or equal to 6.0 when viewed from a side of the first layered film.

[0007] According to another embodiment of the present disclosure, a window for a sensing system includes a substrate comprising a first surface and a second surface, the first surface and the second surface being primary surfaces of the substrate. The window also includes a first layered film disposed on the first surface of the substrate, the first layered film comprising alternating layers of one or more higher refractive index materials and one or more lower refractive index materials, wherein refractive indices of the one or more higher refractive index materials of the first layered film are higher than refractive indices of the one or more lower refractive index materials of the first layered film. The window also includes a second layered film disposed on the second surface of the substrate, the second layered film comprising alternating layers of one or more higher refractive index materials and one or more lower refractive index materials, wherein refractive indices of the one or more higher refractive index materials of the second layered film are higher than refractive indices of the one or more lower refractive index materials of the second layered film, wherein the one or more higher refractive index materials of the second layered film comprises silicon. The window exhibits a maximum hardness, measured at the first layered film and by the Berkovich Indenter Hardness Test, of at least 8 GPa. The quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films are configured so that the window has: an average reflectance, calculated over a 50 nm wavelength range of interest between 1400 nm and 1600 nm, of less than 1% for light incident on the first surface and the second surface at angles of less than or equal to 15°; and an average percentage transmittance, calculated over a 50 nm wavelength range of interest between 1400 nm and 1600 nm, of greater than 90% for light incident on the first surface and the second surface at angles of incidence of less than or equal to 15°.

[0008] Additional features and advantages will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the embodiments as described herein, including the detailed description which follows, the claims, as well as the appended drawings.

[0009] It is to be understood that both the foregoing general description and the following detailed description are merely exemplary, and are intended to provide an overview or framework to understanding the nature and character of the claims. The accompanying drawings are included to provide a further understanding, and are incorporated in and constitute a part of this specification. The drawings illustrate one or more embodiments, and together with the description serve to explain principles and operation of the various embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG. 1 is a side view of a vehicle in an external environment, illustrating a LIDAR system on a roof of the vehicle and another LIDAR system on a forward portion of the vehicle, according to one or more embodiments of the present disclosure;

[0011] FIG. 2 is a schematic view of one of the LIDAR systems of FIG. 1, illustrating an electromagnetic radiation emitter and sensor in an enclosure, and the electromagnetic radiation emitter and sensor emitting electromagnetic radiation that exits the enclosure through a window and returns as reflected radiation through the window, according to one or more embodiments of the present disclosure;

[0012] FIG. 3 is a cross-sectional view of the window of FIG. 2 taken at area III of FIG. 2, illustrating the window including a substrate with a layered film over a first surface of the substrate, and a second layered film over a second surface of the substrate, according to one or more embodiments of the present disclosure;

[0013] FIG. 4 is a cross-sectional view of the window of FIG. 3 taken at area IV of FIG. 3, illustrating the layered film including alternating layers of one or more higher refractive index materials and one or more lower refractive index materials with a layer of the one or more lower refractive index materials providing a terminal surface closest to the external environment, according to one or more embodiments of the present disclosure;

[0014] FIG. 5 is a cross-sectional view of the window of FIG. 3 taken at area V of FIG. 3, illustrating the second layered film including alternating layers of one or more higher refractive index materials and one or more lower refractive index materials with a layer of the one or more lower refractive index materials providing a terminal surface closest to the electromagnetic radiation emitter and sensor, according to one or more embodiments of the present disclosure;

[0015] FIG. 6 is a graph of refractive index and extinction coefficient as a function of wavelength for a silicon material used in a second layered film of a first example window comprising first and second layered films disposed on a glass substrate, according to one or more embodiments of the present disclosure;

[0016] FIG. 7 is a graph of two-surface visible-to-infrared performance, in terms of modelled reflectance and transmittance, for light normally incident on the first example window throughout a wavelength range of 400 nm to 1600 nm, according to one or more embodiments of the present disclosure;

[0017] FIG. 8 is a graph of a modeled two-surface transmittance for light in an infrared wavelength range of interest from 1500 nm to 1600 nm that is normally incident on the first layered film of the example window, according to one or more embodiments of the present disclosure;

[0018] FIG. 9 is a graph of a modeled two-surface transmittance for s and p polarized light in an infrared wavelength range of interest from 1500 nm to 1600 nm that is incident on the first layered film of the first example window at a 60 degree angle of incidence, according to one or more embodiments of the present disclosure;

[0019] FIG. 10 is a graph of a modelled two-surface reflectance for light in an infrared wavelength range of interest from 1500 nm to 1600 nm that is normally incident on the first and second layered films of the first example window, according to one or more embodiments of the present disclosure;

[0020] FIG. 11 is a graph of a modelled two-surface transmittance for light in the visible spectrum that is normally incident on the first layered film of the first example window, according to one or more embodiments of the present disclosure;

[0021] FIG. 12A is a graph of CIELAB color space values a* and b* for light incident on the first layered film of the first example window at a plurality of angles of incidence, according to one or more embodiments of the present disclosure;

[0022] FIG. 12B is a graph of the CIELAB lightness value L* for light incident on the first layered film of the first example window at a plurality of angles of incidence, according to one or more embodiments of the present disclosure; [0023] FIG. 13 is a graph if nanoindentation hardness as a function of depth into first layered films of two samples constructed according to the first example window, according to one or more embodiments of the present disclosure;

[0024] FIG. 14 is a graph of refractive index and extinction coefficient as a function of wavelength for a silicon material used in a second layered film of a second example window comprising first and second layered films disposed on a glass substrate, according to one or more embodiments of the present disclosure;

[0025] FIG. 15 is a graph of two-surface visible-to-infrared performance, in terms of modelled reflectance and transmittance, for light normally incident on the second example window throughout a wavelength range of 400 nm to 1600 nm, according to one or more embodiments of the present disclosure;

[0026] FIG. 16 is a graph of a modeled two-surface transmittance for light in an infrared wavelength range of interest from 1500 nm to 1600 nm that is normally incident on the first layered film of the second example window, according to one or more embodiments of the present disclosure;

[0027] FIG. 17 is a graph of a modeled two-surface transmittance for s and p polarized light in an infrared wavelength range of interest from 1500 nm to 1600 nm that is incident on the first layered film of the second example window at a 60 degree angle of incidence, according to one or more embodiments of the present disclosure;

[0028] FIG. 18 is a graph of a modelled two-surface reflectance for light in an infrared wavelength range of interest from 1500 nm to 1600 nm that is normally incident on the first and second layered films of the second example window, according to one or more embodiments of the present disclosure;

[0029] FIG. 19 is a graph of a modelled two-surface transmittance for light in the visible spectrum that is normally incident on the first layered film of the second example window, according to one or more embodiments of the present disclosure;

[0030] FIG. 20 A is a graph of CIELAB color space values a* and b* for light incident on the first layered film of the second example window at a plurality of angles of incidence, according to one or more embodiments of the present disclosure;

[0031] FIG. 20B is a graph of the CIELAB lightness value L* for light incident on the first layered film of the second example window at a plurality of angles of incidence, according to one or more embodiments of the present disclosure; [0032] FIG. 21 is a graph of two-surface visible-to-infrared performance, in terms of modelled reflectance and transmittance, for light normally incident on a third example window comprising a first layered film and a second layered film, throughout a wavelength range of 400 nm to 1600 nm, according to one or more embodiments of the present disclosure;

[0033] FIG. 22 is a graph of a modeled two-surface transmittance for light in an infrared wavelength range of interest from 1500 nm to 1600 nm that is normally incident on the first layered film of the third example window, according to one or more embodiments of the present disclosure;

[0034] FIG. 23 is a graph of a modeled two-surface transmittance for s and p polarized light in an infrared wavelength range of interest from 1500 nm to 1600 nm that is incident on the first layered film of the third example window at a 60 degree angle of incidence, according to one or more embodiments of the present disclosure;

[0035] FIG. 24 is a graph of a modelled two-surface reflectance for light in an infrared wavelength range of interest from 1500 nm to 1600 nm that is normally incident on the first and second layered films of the third example window, according to one or more embodiments of the present disclosure;

[0036] FIG. 25 is a graph of a modelled two-surface transmittance for light in the visible spectrum that is normally incident on the first layered film of the third example window, according to one or more embodiments of the present disclosure;

[0037] FIG. 26A is a graph of CIELAB color space values a* and b* for light incident on the first layered film of the third example window at a plurality of angles of incidence, according to one or more embodiments of the present disclosure;

[0038] FIG. 26B is a graph of the CIELAB lightness value L* for light incident on the first layered film of the third example window at a plurality of angles of incidence, according to one or more embodiments of the present disclosure;

[0039] FIG. 27 is a graph of two-surface visible-to-infrared performance, in terms of modelled reflectance and transmittance, for light normally incident on a fourth example window comprising a first layered film and a second layered film, throughout a wavelength range of 400 nm to 1600 nm, according to one or more embodiments of the present disclosure;

[0040] FIG. 28 is a graph of a modeled two-surface transmittance for light in an infrared wavelength range of interest from 1500 nm to 1600 nm that is normally incident on the first layered film of the fourth example window, according to one or more embodiments of the present disclosure;

[0041] FIG. 29 is a graph of a modeled two-surface transmittance for s and p polarized light in an infrared wavelength range of interest from 1500 nm to 1600 nm that is incident on the first layered film of the fourth example window at a 60 degree angle of incidence, according to one or more embodiments of the present disclosure;

[0042] FIG. 30 is a graph of a modelled two-surface reflectance for light in an infrared wavelength range of interest from 1500 nm to 1600 nm that is normally incident on the first and second layered films of the fourth example window, according to one or more embodiments of the present disclosure;

[0043] FIG. 31 is a graph of a modelled two-surface transmittance for light in the visible spectrum that is normally incident on the first layered film of the fourth example window, according to one or more embodiments of the present disclosure;

[0044] FIG. 32A is a graph of CIELAB color space values a* and b* for light incident on the first layered film of the fourth example window at a plurality of angles of incidence, according to one or more embodiments of the present disclosure;

[0045] FIG. 32B is a graph of the CIELAB lightness value L* for light incident on the first layered film of the fourth example window at a plurality of angles of incidence, according to one or more embodiments of the present disclosure;

[0046] FIG. 33 is a graph of two-surface visible-to-infrared performance, in terms of modelled reflectance and transmittance, for light normally incident on a fifth example window comprising a first layered film and a second layered film, throughout a wavelength range of 400 nm to 1600 nm, according to one or more embodiments of the present disclosure;

[0047] FIG. 34 is a graph of a modeled two-surface transmittance for light in an infrared wavelength range of interest from 1500 nm to 1600 nm that is normally incident on the first layered film of the fifth example window, according to one or more embodiments of the present disclosure;

[0048] FIG. 35 is a graph of a modeled two-surface transmittance for s and p polarized light in an infrared wavelength range of interest from 1500 nm to 1600 nm that is incident on the first layered film of the fifth example window at a 60 degree angle of incidence, according to one or more embodiments of the present disclosure; [0049] FIG. 36 is a graph of a modelled two-surface reflectance for light in an infrared wavelength range of interest from 1500 nm to 1600 nm that is normally incident on the first and second layered films of the fifth example window, according to one or more embodiments of the present disclosure;

[0050] FIG. 37 is a graph of a modelled two-surface transmittance for light in the visible spectrum that is normally incident on the first layered film of the fifth example window, according to one or more embodiments of the present disclosure;

[0051] FIG. 38A is a graph of CIELAB color space values a* and b* for light incident on the first layered film of the fifth example window at a plurality of angles of incidence, according to one or more embodiments of the present disclosure;

[0052] FIG. 38B is a graph of the CIELAB lightness value L* for light incident on the first layered film of the fifth example window at a plurality of angles of incidence, according to one or more embodiments of the present disclosure;

[0053] FIG. 39 is a graph of refractive index and extinction coefficient as a function of wavelength for a silicon material used in a second layered film of a sixth example window comprising first and second layered films disposed on a glass substrate, according to one or more embodiments of the present disclosure;

[0054] FIG. 40 is a graph of two-surface visible-to-infrared performance, in terms of modelled transmittance, for light incident on a sixth example window comprising a first layered film and a second layered film, throughout a wavelength range of 400 nm to 1600 nm, according to one or more embodiments of the present disclosure;

[0055] FIG. 41 is a graph of two-surface visible-to-infrared performance, in terms of modelled reflectance, for light incident on a sixth example window comprising a first layered film and a second layered film, throughout a wavelength range of 400 nm to 1600 nm, according to one or more embodiments of the present disclosure;

[0056] FIG. 42 is a graph of CIELAB color space values a* and b* for light incident on the first layered film of the sixth example window at a plurality of angles of incidence, according to one or more embodiments of the present disclosure;

[0057] FIG. 43 is graph of two-surface infrared performance, in terms of modelled transmittance, for light incident on a seventh example window comprising a first layered film and a second layered film, throughout a wavelength range 1500 nm to 1600 nm, according to one or more embodiments of the present disclosure; [0058] FIG. 44 is a graph of two-surface infrared performance, in terms of modelled reflectance, for light incident on a seventh example window comprising a first layered film and a second layered film, throughout a wavelength range of 1500 nm to 1600 nm, according to one or more embodiments of the present disclosure;

[0059] FIG. 45 is a graph of two-surface visible-to-infrared performance, in terms of modelled transmittance, for light incident on a seventh example window comprising a first layered film and a second layered film, throughout a wavelength range of 350 nm to 1600 nm, according to one or more embodiments of the present disclosure;

[0060] FIG. 46 is a graph of two-surface visible-to-infrared performance, in terms of modelled reflectance, for light incident on a seventh example window comprising a first layered film and a second layered film, throughout a wavelength range of 350 nm to 1600 nm, according to one or more embodiments of the present disclosure;

[0061] FIG. 47 is a graph of two-surface visible performance, in terms of modelled transmittance, for light incident on a seventh example window comprising a first layered film and a second layered film, throughout a wavelength range of 400 nm to 700 nm, according to one or more embodiments of the present disclosure;

[0062] FIG. 48 is a graph of CIELAB color space values a* and b* for light incident on the first layered film of the seventh example window at a plurality of angles of incidence, according to one or more embodiments of the present disclosure; and

[0063] FIG. 49 is a graph of the CIELAB lightness value L* for light incident on the first layered film of the seventh example window at a plurality of angles of incidence, according to one or more embodiments of the present disclosure.

DETAILED DESCRIPTION

[0064] Reference will now be made in detail to embodiments of windows for use in LIDAR sensors. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts. The windows comprise described herein may include first and second layered films that are constructed of alternating layers of higher and lower refractive index materials and configured to provide relatively high transmittance and low reflectance in a desired infrared wavelength range of interest. When the window is installed in a LIDAR system, the first layered film may face away from the sensor/electromagnetic radiation emitter and be exposed to an external environment, while the second layered film may face the sensor/electromagnetic radiation emitter. That is, when the LIDAR system is viewed from the outside, an observer may view the first layered film. Light emitted by the electromagnetic radiation emitter may be initially incident on the second layered film prior to propagating through the substrate. In accordance with the present disclosure, the fist layered films of the windows described herein may include one or more scratch resistant layers that are relatively thick (e.g., greater than or equal to 500 nm) of a high refractive index material. The scratch resistant layer may be embedded within the first layered film such that the window comprises a maximum nanoindentation hardness of greater than or equal to 8 GPa (e.g., greater than or equal to 10 GPa, greater than or equal to 12 GPa, greater than or equal to 14 GPa) when measured at the first layered film by the Berkovich Indenter Hardness Test. Such nanoindentation hardness beneficially provides scratch resistance and improves performance of the LIDAR system.

[0065] In aspects, the alternating layers of the first and second layered films of the windows described herein are also constructed to provide optical performance attributes that are desirable for operation of the LIDAR system in the infrared spectrum. In embodiments, the quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films are configured so that the window has an average percentage transmittance, calculated over a 50 nm wavelength range of interest from 1400 nm to 1600 nm, of greater than 90% (e.g., greater than or equal to 95%) for light incident on the first surface and the second surface at angles of incidence of 15° or less. The quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films may be configured so that the window also comprises an average percentage P- polarization transmittance and S-Polarization transmittance, calculated over a 50 nm wavelength range of interest from 1400 nm to 1600 nm, of greater than 85% (e.g., greater than or equal to 90%, greater than or equal to 93%) for light incident on the first surface and the second surface at an angle of incidence of 60 degrees or less.

[0066] In further aspects, the first and second layered films of the windows described herein may also be structured to have relatively low reflectance and transmittance of visible light, thereby providing the window with an aesthetically pleasing dark appearance and eliminating signal noise. In embodiments, for example, the quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films are configured so that the window has an average percentage transmission, calculated from 400 nm to 700 nm, of less than 5% for light incident on the first layered film at angles of incidence of 15° or less'. Such low transmission of visible light may be achieved by incorporating silicon layers into the second layered film in the amounts described herein. As a result, when viewed from the first layered film (i.e., from outside the LIDAR sensor), the windows described herein may exhibit CIELAB lightness L* values of less than or equal to 45 (e.g., less than or equal to 40, less than or equal to 35, less than or equal to 30) when viewed from angles of 60 degrees or less. The windows described herein may also exhibit CIELAB color space a* and b* values that are greater than or equal to -6 and less than or equal to 6 (e.g., greater than or equal to -5 and less than or equal to 5, greater than or equal to -4 and less than or equal to 4, greater than or equal to -3 and less than or equal to 3, greater than or equal to -2.5 and less than or equal to 2.5) when viewed from the first layered film. The perceived color of the window, when viewed from the side of the first layered film, may be black or relatively dark so as to render the window less noticeable to outside observers.

[0067] As such, the windows described herein provide durable anti-reflection performance for a desired wavelength range of interest from 1400 nm to 1600 nm, while providing an aesthetically pleasing and performance enhancing black or dark appearance. The windows described herein may improve LIDAR sensor performance over certain existing sensors by preventing visible light from being incident on the sensors and improving signal-to-noise ratio. Moreover, the windows described herein may reduce unwanted glare that is visible to outside observers.

[0068] Unless otherwise noted, the total, specular, and average reflectance values provided herein are two-surface reflectance values, representing a total reflectance of an entire window, including the reflectance associated with each material interface in the window (e.g., between air and the layered films, between the layered films and the substrate, etc.). Unless otherwise noted, reflectance values provided in the infrared are measured from the side of the second layered film described herein (e.g., from the side positioned facing a sensor and emitter of a LIDAR system) and reflectance values provided in the visible are measured from the side of the first layered film described herein (e.g., from the side positioned facing an external environment of a LIDAR system).

[0069] Unless otherwise specified herein, average transmittance and reflectance values are calculated using percentage reflectance and transmittance values at various wavelengths within a specified wavelength range. Average reflectance transmittance values may be calculated by measuring at least 3 reflectance and transmittance values within a desired wavelength range, and averaging those values. [0070] Unless otherwise noted herein, CIELAB color space a* and b* and lightness L* values are measured/simulated using a D65 illuminate for a standard observer with a 10- degree field of view.

[0071] As used herein, the terms “dark appearance” or “black appearance” refer to the reflected appearance of the window when viewed from an external surface. Windows having a dark appearance or black appearance in accordance with the present disclosure comprise CIELAB lightness L* values of less than 45 when viewed from angles 60° or less.

[0072] Unless otherwise expressly stated, it is in no way intended that any method set forth herein be construed as requiring that its steps be performed in a specific order. Accordingly, where a method claim does not actually recite an order to be followed by its steps, or it is not otherwise specifically stated in the claims or descriptions that the steps are to be limited to a specific order, it is no way intended that an order be inferred, in any respect. This holds for any possible non-express basis for interpretation, including: matters of logic with respect to arrangement of steps or operational flow; plain meaning derived from grammatical organization or punctuation; the number or type of embodiments described in the specification.

[0073] As used herein, the term “and/or,” when used in a list of two or more items, means that any one of the listed items can be employed by itself, or any combination of two or more of the listed items can be employed. For example, if a composition is described as containing components A, B, and/or C, the composition can contain A alone; B alone; C alone; A and B in combination; A and C in combination; B and C in combination; or A, B, and C in combination.

[0074] Modifications of the disclosure will occur to those skilled in the art and to those who make or use the disclosure. Therefore, it is understood that the embodiments shown in the drawings and described above are merely for illustrative purposes and not intended to limit the scope of the disclosure, which is defined by the following claims, as interpreted according to the principles of patent law, including the doctrine of equivalents.

[0075] In this document, relational terms, such as first and second, top and bottom, and the like, are used solely to distinguish one entity or action from another entity or action, without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms “comprises,” “comprising,” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by “comprises . . . a” does not, without more constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.

[0076] As used herein, the term “about” means that amounts, sizes, formulations, parameters, and other quantities and characteristics are not and need not be exact, but may be approximate and/or larger or smaller, as desired, reflecting tolerances, conversion factors, rounding off, measurement error and the like, and other factors known to those of skill in the art. When the term “about” is used in describing a value or an end-point of a range, the disclosure should be understood to include the specific value or end-point referred to. Whether or not a numerical value or end-point of a range in the specification recites “about,” the numerical value or end-point of a range is intended to include two embodiments: one modified by “about,” and one not modified by “about.” It will be further understood that the end-points of each of the ranges are significant both in relation to the other end-point, and independently of the other end-point.

[0077] The term “formed from” can mean one or more of comprises, consists essentially of, or consists of. For example, a component that is formed from a particular material can comprise the particular material, consist essentially of the particular material, or consist of the particular material.

[0078] As also used herein, the terms “article,” “glass-article,” “ceramic-article,” “glassceramics,” “glass elements,” “glass-ceramic article” and “glass-ceramic articles” may be used interchangeably, and in their broadest sense, to include any object made wholly or partly of glass and/or glass-ceramic material.

[0079] The term “disposed” is used herein to refer to a layer or sub-layer that is coated, deposited, formed, or otherwise provided onto a surface. The term disposed can include layers/sub-layers provided in direct contact with adjacent layers/sub-layers or layers/sub- layers separated by intervening material which may or may not form a layer.

[0080] Unless otherwise noted herein, refractive indices of the materials described herein are measured at 1550 nm.

[0081] Referring now to FIG. 1, a vehicle 10 includes one or more LIDAR systems 12. The one or more LIDAR systems 12 can be disposed anywhere on or within the vehicle 10. For example, the one or more LIDAR systems 12 can be disposed on a roof 14 of the vehicle 10 and/or a forward portion 16 of the vehicle 10. [0082] Referring now to FIG. 2, each of the one or more LIDAR systems 12 include an electromagnetic radiation emitter and sensor 18, as known in the art, which may be enclosed in an enclosure 20. The electromagnetic radiation emitter and sensor 18 emits electromagnetic radiation 22 having a wavelength or range of wavelengths. The emitted radiation 22 exits the enclosure 20 through a window 24, which is in the path of the emitted electromagnetic radiation. If an object (not illustrated) in an external environment 26 is in the path of the emitted radiation 22, the emitted radiation 22 will reflect off of the object and return to the electromagnetic radiation emitter and sensor 18 as reflected radiation 28. The reflected radiation 28 again passes through the window 24 to reach the electromagnetic radiation emitter and sensor 18. In embodiments, the emitted radiation 22 and the reflected radiation 28 may include light within a suitable wavelength range of interest. For example, in embodiments, the emitted radiation 22 and reflected radiation 28 may be greater than or equal to 1400 nm and less than or equal to 1600 nm (e.g., greater than or equal to 1500 nm and less than or equal to 1600 nm, greater than or equal to 1525 nm and less than or equal to 1575 nm, approximately 1550 nm, 1550 nm). Electromagnetic radiation other than the reflected radiation 28 (such as electromagnetic radiation having wavelengths in the visible spectrum, portions of the ultraviolet range) may also interact with the window 24. As described herein, the window 24 may include layered films comprising layer structures that are designed to absorb light in the visible spectrum while also reflecting relatively low amounts of light in the visible spectrum, such that the window has a dark or black appearance when viewed from outside of the enclosure 20.

[0083] The “visible spectrum” is the portion of the electromagnetic spectrum that is visible to the human eye and generally refers to electromagnetic radiation having a wavelength within the range of about 380nm or 400nm to about 700nm. The “ultraviolet range” is the portion of the electromagnetic spectrum having wavelengths between about lOnm and about 400nm. The “infrared range” of the electromagnetic spectrum begins at about 700nm and extends to longer wavelengths. The sun generates solar electromagnetic radiation, commonly referred to as “sunlight,” having wavelengths that fall within all three of those ranges.

[0084] Referring now to FIG. 3, the window 24 for each of the one or more LIDAR systems 12 includes a substrate 30. The substrate 30 includes a first surface 32 and a second surface 34. The first surface 32 and the second surface 34 are the primary surfaces of the substrate 30. The first surface 32 is closest to the external environment 26. The second surface 34 is closest to the electromagnetic radiation emitter and sensor 18. The emitted radiation 22 encounters the second surface 34 before the first surface 32. The reflected radiation 28 encounters the first surface 32 before the second surface 34. The substrate 30 further includes a first layered film 36 disposed on the first surface 32 of the substrate 30 and a second layered film 38 is disposed on the second surface 34 of the substrate 30. It should be understood that the window 24 as described herein is not limited to vehicular applications, and can be used for whatever application the window 24 would be useful to provide improved impact and optical performance, as described further herein.

[0085] The substrate 30 may be constructed from a variety of different materials in accordance with the present disclosure. In embodiments, the substrate 30 may be constructed of any type of glass, a glass ceramic, ceramic, or a suitable polymer-based material. Various example structures and compositions of the substrate 30 are now described in greater detail.

[0086] In embodiments, the substrate 30 includes a glass composition or is a glass article. The substrate 30, for example, can include a borosilicate glass, an aluminosilicate glass, sodalime glass, chemically strengthened borosilicate glass, chemically strengthened aluminosilicate glass, or chemically strengthened soda-lime glass. In embodiments, the glass composition of the substrate 30 is capable of being chemically strengthened by an ionexchange process. In embodiments, the composition may be free of lithium ions.

[0087] An alkali aluminosilicate glass composition suitable for the substrate 30 comprises alumina, at least one alkali metal and, In embodiments, greater than 50 mol. % SiCh, in other embodiments at least 58 mol. % SiCh, and in still other embodiments at least 60 mol. % SiCh, wherein the ratio (A12O3+B2O3)/S _mo difiers (i.e. , sum of modifiers) is greater than 1, wherein the ratio of the components are expressed in mol. % and the modifiers are alkali metal oxides. This composition, in particular embodiments, comprises: 58-72 mol. % SiCh; 9-17 mol. % AI2O3; 2-12 mol. % B2O3; 8-16 mol. % Na2O; and 0-4 mol. % K2O, wherein the ratio (A12O3+B2O3)/Smodifiers (i.e., sum of modifiers) is greater than 1.

[0088] Another suitable alkali aluminosilicate glass composition for the substrate 30 comprises: 64-68 mol. % SiCh; 12-16 mol. % Na2O; 8-12 mol. % AI2O3; 0-3 mol. % B2O3; 2- 5 mol. % K2O; 4-6 mol. % MgO; and 0-5 mol. % CaO, wherein: 66 mol. %=SiO2+B2C>3+CaO=69 mol. %; Na20+K20+B203+Mg0+Ca0+Sr0>10 mol. %; 5 mol. %^MgO+CaO+SrO^8 mol. %; (Na ₂ O+B ₂ O3)— A1 ₂ O ₃ ^2 mol. %; 2 mol. %gNa ₂ O— AhO3^6 mol. %; and 4 mol. %^(Na20+K20)-A1203^10 mol. %. [0089] Another suitable alkali aluminosilicate glass composition for the substrate 30 comprises: 2 mol. % or more of AI2O3 and/or ZrCh, or 4 mol. % or more of AI2O3 and/or ZrO ₂ .

[0090] One example glass composition comprises SiO2, B2O3, and Na2O, where (SiO2+B2O3)^66 mol. %, and Na2O^9 mol. %. In an embodiment, the composition includes at least 6 wt. % aluminum oxide. In a further embodiment, the composition of one or more alkaline earth oxides, such as a content of alkaline earth oxides, is at least 5 wt. %. Suitable compositions, In embodiments, further comprise at least one of K2O, MgO, and CaO. In a particular embodiment, the composition of the substrate 30 comprises 61-75 mol. % SiCh; 7- 15 mol. % AI2O3; 0-12 mol. % B2O3; 9-21 mol. % Na2O; 0-4 mol. % K2O; 0-7 mol. % MgO; and 0-3 mol. % CaO.

[0091] A further example composition suitable for the substrate 30 comprises: 60-70 mol. % SiO2; 6-14 mol. % AI2O3; 0-15 mol. % B2O3; 0-15 mol. % I 2O; 0-20 mol. % Na2O; 0-10 mol. % K2O; 0-8 mol. % MgO; 0-10 mol. % CaO; 0-5 mol. % ZrO2; 0-1 mol. % SnO2; 0-1 mol. % CeO2; less than 50 ppm AS2O3; and less than 50 ppm Sb2O3; where 12 mol. %^(Li20+Na20+K20)^20 mol. % and 0 mol. %^(MgO+CaO)^10 mol. %.

[0092] A still further example glass composition suitable for the substrate 30 comprises: 63.5-66.5 mol. % SiO2; 8-12 mol. % AI2O3; 0-3 mol. % B2O3; 0-5 mol. % Li2O; 8-18 mol. % Na ₂ O; 0-5 mol. % K ₂ O; 1-7 mol. % MgO; 0-2.5 mol. % CaO; 0-3 mol. % ZrO ₂ ; 0.05-0.25 mol. % SnO2; 0.05-0.5 mol. % CeO2; less than 50 ppm AS2O3; and less than 50 ppm Sb2O3; where 14 mol. %^(Li2O+Na2O+K2O)^18 mol. % and 2 mol. %^(MgO+CaO)^7 mol. %.

[0093] The substrate 30 may be substantially planar or sheet-like, although other embodiments may utilize a curved or otherwise shaped or sculpted substrate. The length and width of the substrate 30 can vary according to the dimensions required for the window 24. The substrate 30 can be formed using various methods, such as float glass processes and down-draw processes such as fusion draw and slot draw. The substrate 30 can be used in a non-strengthened state. A commercially available example of a suitable non- strengthened substrate 30 for the window 24 is Coming® glass code 2320, which is a sodium aluminosilicate glass substrate.

[0094] The glass forming the substrate 30 can be modified to have a region contiguous with the first surface 32 and/or a region contiguous with the second surface 34 to be under compressive stress (“CS”). In such a circumstance, the region(s) under compressive stress extends from the first surface 32 and/or the second surface 34 to a depth(s) of compression. This generation of compressive stress further creates a central region that is under a tensile stress, having a maximum value at the center of the central region, referred to as central tension or center tension (CT). The central region extends between the depths of compression, and is under tensile stress. The tensile stress of the central region balances or counteracts the compressive stresses of the regions under compressive stress. As used herein, the terms “depth of compression” and “DOC” refer to the depth at which the stress within the substrate 30 changes from compressive to tensile stress. At the depth of compression, the stress crosses from a positive (compressive) stress to a negative (tensile) stress and thus has a value of zero. The depth of compression protects the substrate 30 from the propagation of flaws introduced by sharp impact to the first and/or second surfaces 32, 34 of the substrate 30, while the compressive stress minimizes the likelihood of a flaw growing and penetrating through the depths of compression. In embodiments, the depths of compression are each at least 20 pm. In embodiments, the absolute value of the maximum compressive stress CS within the regions is at least 200 MPa, at least about 400 MPa, at least 600 MPa, or up to about 1000 MPa.

[0095] Two methods for extracting detailed and precise stress profiles (stress as a function of depth) for a substrate 30 with regions under compressive stress are disclosed in U.S. Patent No. 9,140,543, entitled “Systems and Methods for Measuring the Stress Profile of Ion- Exchanged Glass,” filed by Douglas Clippinger Allan et al. on May 3, 2012, and claiming priority to U.S. Provisional Patent Application No. 61/489,800, having the same title, and filed on May 25, 2011, the contents of which are incorporated herein by reference in their entirety.

[0096] In embodiments, generating the region(s) of the substrate 30 under compressive stress includes subjecting the substrate 30 to an ion-exchange chemical tempering process (chemical tempering is often referred to as “chemical strengthening”). In the ion-exchange chemical tempering process, ions at or near the first and second surfaces 32, 34 of the substrate 30 are replaced by — or exchanged with — larger ions usually having the same valence or oxidation state. In those embodiments in which the substrate 30 comprises, consists essentially of, or consists of an alkali aluminosilicate glass, an alkali borosilicate glass, an alkali aluminoborosilicate glass, or an alkali silicate glass, ions in the surface layer of the glass and the larger ions are monovalent alkali metal cations, such as Na ⁺ (when Li ⁺ is present in the glass), K ⁺ , Rb ⁺ , and Cs ⁺ . Alternatively, monovalent cations in, at, or near the first and second surfaces 32, 34 may be replaced with monovalent cations other than alkali metal cations, such as Ag ⁺ or the like.

[0097] In embodiments, the ion-exchange process is carried out by immersing the substrate 30 in a molten salt bath containing the larger ions to be exchanged with the smaller ions in the substrate 30. It will be appreciated by those skilled in the art that parameters for the ionexchange process, including, but not limited to, bath composition and temperature, immersion time, the number of immersions of the glass in a salt bath (or baths), use of multiple salt baths, and additional steps such as annealing, washing and the like, are generally determined by the composition of the substrate 30 and the desired depths of compression and compressive stress of the substrate 30 that result from the strengthening operation. By way of example, ion-exchange of alkali metal-containing glass substrates may be achieved by immersion in at least one molten bath containing a salt such as, but not limited to, nitrates, sulfates, and chlorides of the larger alkali metal ion. In embodiments, the molten salt bath comprises potassium nitrate (0-100 wt%), sodium nitrate (0-100 wt%), and lithium nitrate (0- 12 wt%), the combined potassium nitrate and sodium nitrate having a weight percentage within the range of 88 wt% to 100 wt%. In embodiments, the temperature of the molten salt bath typically is in a range from about 350°C up to about 500°C, while immersion times range from about 15 minutes up to about 40 hours, including from about 20 minutes to about 10 hours. However, temperatures and immersion times different from those described above may also be used. The substrate 30 may be acid polished or otherwise treated to remove or reduce the effect of surface flaws.

[0098] In embodiments, the substrate 30 includes a glass-ceramic material having both a glassy phase and a ceramic phase. Illustrative glass-ceramics include those materials where the glass phase is formed from a silicate, borosilicate, aluminosilicate, or boroaluminosilicate, and the ceramic phase is formed from P-spodumene, P-quartz, nepheline, kalsilite, or carnegieite. “Glass-ceramics” include materials produced through controlled crystallization of glass. Examples of suitable glass-ceramics may include Li2O-A12O3-SiO2 system (i.e., LAS-System) glass-ceramics, MgO-A12O3-SiO2 system (i.e., MAS-System) glass-ceramics, ZnO x A12O3 x nSiO2 (i.e., ZAS system), and/or glass-ceramics that include a predominant crystal phase including P-quartz solid solution, P-spodumene, cordierite, and lithium disilicate. The glass-ceramic substrates may be strengthened using a chemical strengthening process. [0099] In embodiments, the substrate 30 includes a ceramic material such as inorganic crystalline oxides, nitrides, carbides, oxy nitrides, carbo nitrides, and/or the like. Illustrative ceramics include those materials having an alumina, aluminum titanate, mullite, cordierite, zircon, spinel, perovskite, zirconia, ceria, silicon carbide, silicon nitride, silicon aluminum oxynitride, or zeolite phase.

[00100] In embodiments, the substrate 30 includes an organic or suitable polymeric material. Examples of suitable polymers include, without limitation: thermoplastics including polystyrene (PS) (including styrene copolymers and blends), polycarbonate (PC) (including copolymers and blends), polyesters (including copolymers and blends, including polyethyleneterephthalate and polyethyleneterephthalate copolymers), polyolefins (PO) and cyclicpolyolefins (cyclic-PO), polyvinylchloride (PVC), acrylic polymers including polymethyl methacrylate (PMMA) (including copolymers and blends), thermoplastic urethanes (TPU), polyetherimide (PEI) and blends of these polymers with each other. Other exemplary polymers include epoxy, styrenic, phenolic, melamine, and silicone resins.

[00101] In embodiments, the substrate 30 includes a plurality of layers or sub-layers. The layers or sub-layers of the substrate 30 may be the same or different from one another. In embodiments, for example, the substrate 30 comprises a glass laminate structure. In embodiments, the glass laminate structure comprises a first glass pane and a second pane attached to one another via a suitable interlayer (e.g., a polymer interlayer) disposed between the first glass pane and the second glass pane. In embodiments, the glass laminate structure comprises a glass-on-glass laminate structure formed via, for example, the fusion draw process. Glass-polymer laminates are also contemplated and within the scope of the present disclosure. Any material capable of meeting the optical requirements described herein may be used as the substrate 30.

[00102] In embodiments, the substrate 30 exhibits an elastic modulus (or Young’s modulus) in the range from about 30 GPa to about 120 GPa. In some instances, the elastic modulus of the substrate may be in the range from about 30 GPa to about 110 GPa, from about 30 GPa to about 100 GPa, from about 30 GPa to about 90 GPa, from about 30 GPa to about 80 GPa, from about 30 GPa to about 70 GPa, from about 40 GPa to about 120 GPa, from about 50 GPa to about 120 GPa, from about 60 GPa to about 120 GPa, from about 70 GPa to about 120 GPa, and all ranges and sub-ranges therebetween.

[00103] In embodiments, the substrate 30 exhibits an average transmittance over the visible wavelength regime of about 85% or greater, about 86% or greater, about 87% or greater, about 88% or greater, about 89% or greater, about 90% or greater, about 91% or greater or about 92% or greater. In embodiments, the substrate 30 comprises a tinting component (e.g., tinting layer or additive) and may optionally exhibit a color, such as white, black, red, blue, green, yellow, orange etc.

[00104] As depicted in FIG. 3, the substrate 30 has a thickness 35 defined as the shortest straight-line distance between the first surface 32 and the second surface 34. In embodiments, the thickness 35 of the substrate 30 is between about 100 pm and about 5 mm. In embodiments, the substrate 30 can have a physical thickness 35 ranging from about 100 pm to about 500 pm (e.g., 100, 200, 300, 400, or 500 pm). In other embodiments, the thickness 35 ranges from about 500 pm to about 1000 pm (e.g., 500, 600, 700, 800, 900, or 1000 pm). The thickness 35 may be greater than about 1 mm (e.g., about 2, 3, 4, 5 mm, 6 mm, or 7 mm). In one or more specific embodiments, the thickness 35 is 2 mm or less or less than or equal to 1 mm.

[00105] In embodiments, the thickness 35 is uniform (e.g., varies by less than 1% throughout an entirety of the substrate) such that the substrate 35 is in the form of a planar sheet. In embodiments, the thickness 35 is a variable thickness and has a value that varies as a function of position on the substrate 30. The thickness 35 may vary along one or more of its dimensions for aesthetic and/or functional reasons. For example, the edges of the substrate 30 may be thicker as compared to more central regions of the substrate 30. The length, width and physical thickness dimensions of the substrate 30 may also vary according to the application or use of the article 30.

[00106] In embodiments, the substrate 30 includes a visible light absorbing, IR-transmitting material layer. Examples of such materials include infrared transmitting, visible absorbing acrylic sheets, such as those commercially available from ePlastics under the trade names Plexiglas® IR acrylic 3143 and CYRO's ACRYLITE® IR acrylic 1146. Plexiglas® IR acrylic 3143 has a transmissivity of about 0% (at least less than 10%, or less than 1%) for electromagnetic radiation having wavelengths of about 700nm or shorter, but a transmissivity of about 90% (above 85%) for wavelengths within the range of 800nm to about HOOnm (including 905nm).

[00107] In embodiments, the substrate 30 exhibits a refractive index in the range from about 1.45 to about 1.55. In embodiments, the substrate exhibits an average transmission of greater than or equal to 95% (e.g., greater than or equal to 96%, greater than or equal to 97%, greater than or equal to 98%, greater than or equal to 99%, greater than or equal to 99.5%) throughout a spectral range from 1400 nm to 1600 nm.

[00108] Referring now to FIGS. 4 and 5, the first layered film 36 and the second layered film 38 each include a quantity of alternating layers of one or more higher refractive index materials 40 and one or more lower refractive index materials 42. While each of the one or more higher refractive index materials 40 and the one or more lower index materials 42 are identified using the same reference numerals, it should be understood that the utilization of the same reference numeral does not indicate that each of the layers are constructed of the same material or include the same structure. In each of the first and second layered films 36 and 38, different ones of the layers of the respective higher refractive index materials 40 and the lower refractive index materials 42 may include different compositional or structural properties.

[00109] As used herein, the terms “higher refractive index” and “lower refractive index” refer to the values of the refractive index relative to each other, with the refractive index/indices of the one or more higher refractive index materials 40 being greater than the refractive index/indices of the one or more lower refractive index materials 42. In embodiments, the one or more higher refractive index materials 40 have a refractive index from about 1.7 to about 4.0. In embodiments, the one or more lower refractive index materials 42 have a refractive index from about 1.3 to about 1.6. In embodiments, the one or more lower refractive index materials 42 have a refractive index from about 1.3 to about 1.7, while the one or more higher refractive index materials 40 have a refractive index from about 1.9 to about 3.8. The difference in the refractive index of any of the one or more higher refractive index materials 40 and any of the one or more lower refractive index materials 42 may be about 0.1 or greater, 0.2 or greater, 0.3 or greater, 0.4 or greater, 0.5 or greater, 0.6 or greater, 0.7 or greater, 0.8 or greater, 0.9 or greater, 1.0 or greater, 1.5 or greater, 2.0 or greater, 2.1 or greater, 2.2 or greater, or even 2.3 or greater. Because of the difference in the refractive indices of the one or more higher refractive index materials 40 and the one or more lower refractive index materials 42, manipulation of the quantity (number) of alternating layers and their thicknesses can cause selective transmission of electromagnetic radiation within a range of wavelengths through the window 24 and, separately, selective reflectance of electromagnetic radiation within a range of wavelengths off of the first layered film 36. The first layered film 36 (and the second layered film 38, if utilized) is thus a thin-film optical filter having predetermined optical properties configured as a function of the quantity, thicknesses, number, and materials chosen as the one or more higher refractive index materials 40 and the one or more lower refractive index materials 42.

[00110] Some examples of suitable materials for use as the one or more lower refractive index materials 42 include SiCh, AI2O3, GeCh, SiO, A10 _x N _y , SiO _x N _y , Si _u Al _v O _x N _y , MgO, MgAhC , MgF2, BaF2, CaF2, DyFs, YbFs, YF3, and CeF3. The nitrogen content of the materials for use as the one or more lower refractive index materials 42 may be minimized (e.g., in materials such as A10 _x N _y , SiO _x N _y , and Si _u Al _v O _x N _y ).

[00111] Some examples of suitable materials for use as the one or more higher refractive index materials 40 include Si, amorphous silicon (a-Si), SiN _x , SiN _x :H _y , A1N _X , Si _u Al _v O _x N _y , Ta ₂ O ₅ , Nb ₂ O ₅ , AIN, Si ₃ N ₄ , A10 _x N _y , SiO _x N _y , HfO ₂ , TiO ₂ , ZrO ₂ , Y2O3, AI2O3, MoO3, and diamond-like carbon. The oxygen content of the materials for the higher refractive index material 40 may be minimized, especially in SiN _x or A1N _X materials. A10 _x N _y materials may be considered to be oxygen-doped A1N _X , that is they may have an A1N _X crystal structure (e.g., wurtzite) and need not have an A1ON crystal structure. Exemplary preferred A10 _x N _y materials for use as the one or more higher refractive index materials 40 may comprise from about 0 atom % to about 20 atom % oxygen, or from about 5 atom % to about 15 atom % oxygen, while including 30 atom % to about 50 atom % nitrogen. Exemplary preferred SiuAlvO _x N _y for use as the one or more higher refractive index materials 40 may comprise from about 10 atom % to about 30 atom % or from about 15 atom % to about 25 atom % silicon, from about 20 atom % to about 40 atom % or from about 25 atom % to about 35 atom % aluminum, from about 0 atom % to about 20 atom % or from about 1 atom % to about 20 atom % oxygen, and from about 30 atom % to about 50 atom % nitrogen. The foregoing materials may be hydrogenated up to about 30% by weight. Because the refractive indices of the one or more higher refractive index materials 40 and the one or more lower refractive index materials 42 are relative to each other, the same material (such as AI2O3) can be appropriate for the one or more higher refractive index materials 40 depending on the refractive index of the material(s) chosen for the one or more lower refractive index materials 42, and can alternatively be appropriate for the one or more lower refractive index materials 42 depending on the refractive index of the material(s) chosen for the one or more higher refractive index material 40.

[00112] In embodiments, the one or more lower refractive index materials 42 of the first layered film 36 consists of layers of SiCh, and the one or more higher refractive index materials 40 of the first layered film 36 consists of layers of SiO _x N _y or SiN _x . In embodiments, the one or more lower refractive index materials 42 of the first layered film 36 consists of layers of SiCh, and the one or more higher refractive index materials 40 of the first layered film 36 consists of layers of SiN _x or SiO _x N _y , while the one or more lower refractive index materials 42 of the second layered film 38 consists of layers of SiCh and the one or more higher refractive index materials 40 of the second layered film 38 comprises layers of silicon (e.g., a-Si). In embodiments, the one or more lower refractive index materials 42 of the first layered film 36 consists of layers of SiCh, and the one or more higher refractive index materials 40 of the first layered film 36 consists of layers of SiN _x or SiO _x N _y , while the one or more lower refractive index materials 42 of the second layered film 38 consists of layers of SiCh and the one or more higher refractive index materials 40 of the second layered film 38 comprises layers of amorphous silicon (a-Si) and layers of SiN _x or SiO _x N _y .

[00113] The quantity of alternating layers of the higher refractive index material 40 and the lower refractive index material 42 in either the first layered film 36 or the second layered film 38 is not particularly limited. In embodiments, the number of alternating layers within the first layered film 36 is 7 or more, 9 or more, 11 or more, 13 or more, 15 or more, 17 or more, 19 or more, 21 or more, 23 or more, 25 or more, or 51 or more, or 81 or more. In embodiments, the quantity of alternating layers within the second layered film 38 is 7 or more, 9 or more, 11 or more, 13 or more, 15 or more, 17 or more, 19 or more, 21 or more, 23 or more, or 25 or more, or 51 or more, or 81 or more. In embodiments, the quantity of alternating layers in the first layered film 36 and the second layered film 38 collectively forming the window 24, not including the substrate 30, is 14 or more, 20 or more, 26 or more, 32 or more, 38 or more, 44 or more, 50 or more, 72 or more, or 100 or more. In general, the greater the quantity of layers within the first layered film 36 and the second layered film 38, the more narrowly the transmittance and reflectance properties of the window 24 are tailored to one or more specific wavelengths or wavelength ranges.

[00114] Each of the alternating layers of the first layered film 36 and the second layered film 38 has a thickness. The thicknesses selected for each of the alternating layers determines the optical path lengths of light propagating through the window 24 and determines the constructive and destructive interference between different light rays reflected at each material interface of the window 24. Accordingly, the thicknesses of each of the alternating layers, in combination with the refractive index of the one or more higher refractive index materials 40 and the one or more lower refractive index materials 42 determines the reflectance and transmittance spectra of the window 24. [00115] With reference to FIGS. 3, 4, and 5, the reflected radiation 28 first encounters a terminal surface 44 of the first layered film 36 upon interacting with the window 24, and the terminal surface 44 may be open to the external environment 26. In an embodiment, a layer of the one or more lower refractive index materials 42 provides the terminal surface 44 to more closely match the refractive index of the air in the external environment 26 and thus reduce reflection of incident electromagnetic radiation (whether the reflected radiation 28 or otherwise) off of the terminal surface 44. The layer of the one or more lower refractive index materials 42 that provides the terminal surface 44 is the layer of the first layered film 36 that is farthest from the substrate 30. Similarly, in embodiments, when the one or more lower refractive index materials 42 is SiCh, a layer of SiCh, as the one or more lower refractive index materials 42, is disposed directly onto the first surface 32 of the substrate 30, which will typically comprise a large mole percentage of SiCh. Without being bound by theory, it is thought that commonality of SiCb in both the substrate 30 and the adjacent layer of the one or more lower refractive index materials 42 allows for increased bonding strength.

[00116] The emitted radiation 22 first encounters a terminal surface 48 of the second layered film 38 upon interacting with the window 24. In an embodiment, a layer of the one or more lower refractive materials 42 provides the terminal surface 48 to more closely match the refractive index of the air within the enclosure 20 and thus reduce reflection of the incident emitted radiation 22 off of the terminal surface 48. The layer of the one or more lower refractive index materials 42 that provides the terminal surface 48 is the layer of the second layered film 38 that is farthest from the substrate 30. Similarly, in embodiments, when the one or more lower refractive index materials 42 is SiCh, a layer of SiCh, as the one or more lower refractive index materials 42, is disposed directly onto the second surface 34 of the substrate 30.

[00117] Materials that have a relatively high refractive index can simultaneously have a relatively high hardness that provides scratch and impact resistance. An example material that has both high hardness and can be one of the one or more higher refractive index material 40 is SiO _x N _y . Other example materials that have both high hardness and can be the higher refractive index material 40 are SiN _x , SiN _x :H _y , and Sis It has been found that a relatively thick (e.g., greater than or equal to 500 nm) layer of SiO _x N _y (or other suitable higher refractive index material) may increase the scratch and/or damage resistance of the window 24. Such increased scratch and/or damage resistance may be particularly beneficial in the first layered film 36, which may be more likely to encounter impacts of debris from the external environment 26. Accordingly, in embodiments, the first layered film 36 comprises a layer of one of the one or more higher refractive index materials 40 with a thickness greater than or equal to 500 nm (e.g., greater than or equal to 1000 nm, greater than or equal to 1500 nm, greater than or equal to 2000 nm). Such a higher refractive index layer having such a thickness of 500 nm or more is described herein as a “scratch resistant layer.”

[00118] In embodiments, the thickness and location within the first layered film 36 of the scratch resistant layer can be optimized to provide a desired level of hardness and scratch resistance to the first layered film 36 and thus the window 24 as a whole. Different applications of the window 24 could lead to different desired thicknesses for the scratch resistant layer of the higher refractive index material 40 serving as the layer providing the hardness and scratch resistance to the window 24. For example, a window 24 protecting a LIDAR system 12 on a vehicle 10 may require a different thickness for the scratch resistant layer of the higher refractive index material 40 than a window 24 protecting a LIDAR system 12 at an office building. In embodiments, the scratch resistant layer of the higher refractive index material 40 serving as the layer providing the hardness and scratch resistance to the window 24 has a thickness between 500nm and 50000nm, such as between 500nm and lOOOOnm, such as between 2000nm to 5000nm. In embodiments, the thickness of this scratch resistant layer of higher refractive index material 40 has a thickness that is 30% or more, 40% or more, 50% or more, 65% or more, or 85% or more, or 86% or more, of the thickness of the first layered film 36. In general, the scratch resistant layer of the higher refractive index material 40 serving as the layer providing the hardness and scratch resistance to the window 24 will be part of the first layered film 36 facing the external environment 26 rather the second layered film 38 protected by the enclosure 20, although that may not always be so.

[00119] As will be detailed further below, the quantity, thicknesses, number, and materials of the remaining layers of the first layered film 36 and the second layered film 38 can be configured to provide the window 24 with the desired optical properties (transmittance and reflectance of desired wavelengths) almost regardless of the thickness chosen for the scratch resistant layer of the higher refractive index material 40 serving as the layer providing the hardness and scratch resistance to the window 24. This insensitivity of the optical properties of the window 24 as a whole to the thickness of the scratch resistant layer of the higher refractive index material 40 serving as the layer providing the hardness and scratch resistance to the window 24 when materials having relatively low or negligible optical absorption of electromagnetic radiation of the target wavelength or wavelength range (e.g., from 1400 nm to 1600 nm, 1550 nm). For example, Si?N4 only negligibly absorbs electromagnetic radiation in the 700nm to 2000nm wavelength range.

[00120] This general insensitivity allows the scratch resistant layer of the higher refractive index material 40 in the first layered film 36 to have a thickness predetermined to meet specified hardness or scratch resistance requirements. For example, the first layered film 36 for the window 24 utilized at the roof 14 of the vehicle 10 may have different hardness and scratch resistance requirements than the first layered film 36 for the window 24 utilized at the forward portion 16 of the vehicle 10, and thus a different thickness for the scratch resistant layer of the higher refractive index material 40. This can be achieved without significant altering of the transmittance and reflectance properties of the first layered film 36 as a whole. [00121] The hardness of the first layered film 36, and thus the window 24, with the scratch resistant layer of the higher refractive index material 40 can be quantified. In embodiments, the maximum hardness of the window 24, measured at the first layered film 36 with the scratch resistant layer of the higher refractive index material 40, as measured by the Berkovich Indenter Hardness Test, may be about 8 GPa or greater, about 10 GPa or greater, about 12 GPa or greater, about 14 GPa or greater, about 15 GPa or greater, about 16 GPa or greater, or about 18 GPa or greater at one or more indentation depths from 50nm to 2000nm (measured from the terminal surface 44), and even from 2000nm to 5000nm. As used herein, the “Berkovich Indenter Hardness Test” includes measuring the hardness of a material on a surface thereof by indenting the surface with a diamond Berkovich indenter. The Berkovich Indenter Hardness Test includes indenting the terminal surface 44 of the first layered film 36 with the diamond Berkovich indenter to form an indent to an indentation depth in the range from about 50nm to about 2000nm (or the entire thickness of the first layered film 36) and measuring the maximum hardness from this indentation along the entire indentation depth range or a segment of this indentation depth range (e.g., in the range from about lOOnm to about 600nm), generally using the methods set forth in Oliver, W. C.; Pharr, G. M. An improved technique for determining hardness and elastic modulus using load and displacement sensing indentation experiments. J. Mater. Res., Vol. 7, No. 6, 1992, 1564- 1583; and Oliver, W. C.; Pharr, G. M. Measurement of Hardness and Elastic Modulus by Instrument Indentation: Advances in Understanding and Refinements to Methodology. J. Mater. Res., Vol. 19, No. 1, 2004, 3-20. These levels of hardness improve the resistance of the window 24 to impact damage from sand, small stones, debris, and other objects encountered while the LIDAR system 12 is used for its intended purpose, such as with the vehicle 10 (see FIG. 1). Accordingly, these levels of hardness reduce or prevent the optical scattering and reduced performance of the LIDAR system 12 that the impact damage would otherwise cause.

[00122] In embodiments, at least a portion of the first layered film 36 is disposed between the scratch resistant layer of the higher refractive index material 40 and the terminal surface 44. In embodiments, the first layered film 36 comprises a plurality of alternating layers of the one or more lower refractive index materials 42 and the one or more higher refractive index materials 40 between the terminal surface 44 and the scratch resistant layers. Such a stack of alternating layers disposed between the scratch resistant layer and the terminal surface 44 is described herein as the “optical control layers.” In embodiments, the optical control layers, disposed between the scratch resistant layer and the terminal surface 44, have a combined thickness of greater than or equal to 500 nm (e.g., greater than or equal to 600 nm, greater than or equal to 700 nm, greater than or equal to 800 nm, greater than or equal to 900 nm, greater than or equal to 1000 nm, greater than or equal to 1100 nm, greater than or equal to 1200 nm, greater than or equal to 1300 nm). The quantity, composition, and thickness of the optical control layers may be selected to provide desired anti-reflection performance attributes described herein at an operational wavelength of the LIDAR sensor 12 between 1400 nm and 1600 nm. That way, the second layered film 36 may be designed to provide desirable optical performance characteristics in the visible and/or UV spectrum, as described herein.

[00123] In embodiments, at least 25% (e.g., at least 26%, at least 27%, at least 28%, at least 29%, at least 30%) of a thickness 46 of the first layered film 36 is disposed between the scratch resistant layer and the terminal surface 44. It is believed that such a depth of the scratch resistant layer within the first layered film 36 facilitates the first layered film 36 having a relatively high nanoindentation hardness (as measured by the Berkovich Indenter Hardness Test) over a relatively large range of depths within the first layered film 36. In embodiments, the first layered film 36 has a nanoindentation hardness of greater than or equal to 8 GPa from a depth of 250 nm to a depth of 2000 nm within the first layered film 36. In embodiments, the first layered film 36 has a nanoindentation hardness of greater than or equal to 8.5 GPa from a depth of 1000 nm to a depth of 2000 nm within the first layered film 36. Such hardness values facilitate providing scratch and/or damage resistance against flaws having a relatively wide range of depths. [00124] Referring now to FIGS. 4 and 5, the first layered film 36 has a thickness 46, and the second layered film 38 has a thickness 50. The thickness 46 of the first layered film 36, assumed to include the scratch resistant layer of the one or more higher refractive index materials 40, may be about I pm or greater while still providing the transmittance and reflectance properties described herein. In embodiments, the thickness 46 is in the range of 1pm to just over 50pm, including from about 1pm to about 10pm, and from about 2800nm to about 5900nm. The lower bound of about 1pm is approximately the minimum thickness 46 that still provides hardness and scratch resistance to the window 24. The higher bound of thickness 46 is limited by cost and time required to dispose the layers of the first layered film 36 onto the substrate 30. In addition, the higher bound of the thickness 46 is limited to prevent the first layered film 36 from warping the substrate 30, which is dependent upon the thickness of the substrate 30. The thickness 50 of the second layered film 38 can be any thickness deemed necessary to impart the window 24 with the desired transmittance and reflectance properties. In embodiments, the thickness 50 of the second layered film 38 is in the range of about 800nm to about 7000nm.

[00125] While solving the problem discussed above in the background through imparting hardness, impact, and scratch resistance to the window 24 via the maximized thickness of a higher refractive index material 40, the quantity, thicknesses, number, and materials of the layers of the first layered film 36 and the second layered film are configured to also provide a relatively high transmittance of infrared radiation between 1400 nm and 1600 nm through the window 24. In embodiments, the thicknesses, number, and materials of the alternating layers of the first and second layered films 36 and 38 are configured so that the window 24 has an average percentage transmittance, calculated over a 50 nm wavelength range of interest from 1400 nm to 1600 nm, of greater than or equal to 90% (e.g., greater than or equal to 91%, greater than or equal to 92%, greater than or equal to 93%, greater than or equal to 94%, greater than or equal to 95%) for light incident on the first surface 32 and the second surface 34 at angles within 15° of normal to the first surface 32 and the second surface 34.

[00126] In embodiments, the thicknesses, number, and materials of the alternating layers of the first and second layered films 36 and 38 are configured so that the window 24 has an average reflectance, calculated over a 50 nm wavelength range of interest from 1400 nm to 1600 nm, of less than or equal to 0.5% (e.g., less than or equal to 0.4%, less than or equal to 0.3%, less than or equal to 0.2%, less than or equal to 0.1%, less than or equal to 0.08%) for light incident on the first surface 32 and the second surface 34 at angles within 15° of normal to the first surface 32 and the second surface 34. In embodiments, the number, thicknesses, number, and materials of the alternating layers of the first and second layered films 36 and 38 are configured so that the window has an average P polarization transmittance and an average S polarization transmittance, calculated over a 50 nm wavelength range of interest from 1400 nm to 1600 nm, of greater than 85% (e.g., greater than or equal to 86%, greater than or equal to 87%, greater than or equal to 88%, greater than or equal to 89%, greater than or equal to 90%, greater than or equal to 91%, greater than or equal to 92%) for light incident on the first surface 32 and the second 34 surface at angles within 60° of normal (e.g., at angles of incidence from 0° to 60°, from 0° to 50°, from 0° to 40°, from 0° to 30°) to the first surface 32 and the second surface 34. Herein, the term "reflectance" is defined as the percentage of incident optical power within a given wavelength range that is reflected from a material (e.g., the window 24, the substrate 30, the first layered film 36, second layered film 38, or portions thereof).

[00127] In embodiments, the thicknesses, number, and materials of the alternating layers of the first and second layered films 36 and 38 are configured so that the window 24 has an average percentage transmittance, calculated over a 50 nm wavelength range of interest from 1400 nm to 1600 nm, of greater than or equal to 95% (e.g., greater than or equal to 95.5%, greater than or equal to 96%, greater than or equal to 96.5%, greater than or equal to 97.5%, greater than or equal to 98%) for light normally incident on the first surface 32 and the second surface 34. Herein, the term "transmittance" and “percentage transmission” are used interchangeably ad refer to the percentage of incident optical power within a given wavelength range transmitted through a material (e.g., the window 24, the substrate 30, the first layered film 36, the second layered film 38 or portions thereof).

[00128] In embodiments, the thicknesses, number, and materials of the alternating layers of the first and second layered films 36 and 38 are configured so that the window 24 also (in addition to meeting the optical performance requirements in the infrared described herein) has a desired dark appearance. For example, when viewed from the external environment 26 (see FIG. 1), the window 24 may exhibit CIELAB color space a* values that are greater than or equal to -6.0 and less than or equal to 6.0 for light having angles of incidence on the first surface 32 ranging from 0° to 90°. The window 24 may also exhibit CIELAB color space b* values that are greater than or equal to -6.0 and less than or equal to 6.0 (e.g., greater than or equal to -5.0 and less than or equal to 5.0, greater than or equal to -4.0 and less than or equal to 4.0, greater than or equal to -3.0 and less than or equal to 3.0, greater than or equal to -2.5 and less than or equal to 2.5, greater than or equal to -2.5 and less than or equal to 0.)) for light having angles of incidence on the first surface 32 ranging from 0° to 90°. Such color space values may be obtained even in embodiments where the substrate 30 is has a relatively high transmittance (e.g., greater than 90%) and low reflectance (e.g., less than or equal to 22%) throughout the visible spectrum.

[00129] In embodiments, the thicknesses, number, and materials of the alternating layers of the first and second layered films 36 and 38 are configured so that the window 24 has a CIELAB lightness L* value of less than 45 (e.g., less than or equal to 40, less than or equal to 35, less than or equal to 30) when viewed from angles of incidence of less than or equal to 60°. In embodiments, the thicknesses, number, and materials of the alternating layers of the first and second layered films 36 and 38 are configured so that the window 24 has a CIELAB lightness L* value of less than 20 for light that is normally incident on the first layered film 36 and reflected. The aforementioned combination of CIELAB color space and lightness values represent that the window 24 has a relatively dark appearance from a variety of angles of incidence.

[00130] The dark appearance of the window 24 may be achieved by incorporating silicon (e.g., as a-Si) as one of the one or more higher refractive index materials 40 in the second layered film 38. In addition to having a relatively high refractive index (approximately 3.8 at 1550nm), amorphous silicon (a-Si) has a relatively high optical absorption in the ultraviolet range and visible light range, but tolerable optical absorption in the range of 900-1800nm. The thicknesses and quantity of layers of amorphous silicon (a-Si), along with the other layers of the first layered film 36 and second layered film 38 can thus provide a window 24 with low percentage transmittance of electromagnetic radiation in the ultraviolet range and visible light range (due in part to the optical absorbance of the amorphous silicon at those wavelength ranges) but high percentage transmittance in the desired portions of the infrared range. In embodiments, the second layered film 38 includes one or more layers of amorphous silicon (a-Si) as one of the one or more higher refractive index materials 40 while the first layered film 36 does not. Such a structure may be beneficial in that silicon is solely located behind the substrate 30 and thus protected from the external environment 26. As a result, the nanoindentation hardness values described herein may be obtained via incorporation of the scratch resistance layer into the first layered film 36 while the dark appearance may be obtained via incorporation of silicon into the second layered film 38. [00131] In embodiments, the alternating layers of the second layered film 38 formed of silicon have a combined thickness of greater than or equal to 250 nm (e.g., greater than or equal to 300 nm, greater than or equal to 325 nm, greater than or equal to 350 nm, greater than or equal to 375 nm, greater than or equal to 400 nm, greater than or equal to 500 nm). In embodiments, the layers of the second layered film 38 formed of silicon may have a combined thickness of greater than or equal to 250 nm. In embodiments, the combined thickness of the silicon layers in the second layered film constitutes at least 35% (e.g., at least 40%, at least 45%, at least 50%) of the thickness 50 of the second layered film 50. Applicant has found that such a thickness of silicon sufficiently absorbs visible light such that the window 24 possess an average percentage transmission, calculated from 400 nm to 700 nm, of less an 5% (e.g., less than or equal to 4.5%, less than or equal to 4.0%, less than or equal to 3.5%, less than or equal to 3.0%, less than or equal to 2.5%, less than or equal to 2.0%, less than or equal to 1.5%, less than or equal to 1.0% less than or equal to 0.9%, less than or equal to 0.8%, less than or equal to 0.7%, less than or equal to 0.6%, less than or equal to 0.5%, less than or equal to 0.4%, less than or equal to 0.3%, less than or equal to 0.2%, less than or equal to 0.1%) for light incident on the first surface 32 and the second surface 34 at angles within 15° of normal to the first surface 32 and the second surface 34. As such, portions of the reflected radiation 28 (see FIG. 2) containing visible light do not reach the emitter and sensor 18, thereby improving the signal -to-noise ratio of the LIDAR system 12.

[00132] In embodiments, the second layered film 36 comprises two or more layers formed from silicon. In embodiments, at least one of the two or more layers formed from silicon comprises a thickness of greater than or equal to 150 nm (e.g., greater than or equal to 160 nm, greater than or equal to 170 nm, greater than or equal to 180 nm, greater than or equal to 190 nm, greater than or equal to 200 nm). In embodiments, at least two, but less than all, of the two or more layers formed from silicon in the second layered film 36 comprises thicknesses of greater than or equal to 150 nm. In embodiments, at least seven (7) of the alternating layers of the second layered film 38 are disposed between one of the silicon layers having a thickness of 150 nm or more and the second surface 34. In embodiments, silicon layers contained in the second layered film 38 comprising thicknesses that are less than 150 nm from the second surface comprise thicknesses of less than or equal to 70 nm (e.g., less than or equal to 65 nm, less than or equal to 60 nm, less than or equal to 55 nm, less than or equal to 50 nm, less than or equal to 30 nm, less than or equal to 25 nm, less than or equal to 20 nm). It is believed that such separation between the substrate 30 and the relatively thick silicon layers aids in reducing reflectance in the visible spectrum.

[00133] In embodiments, the alternating layers of the first and second layered films 36 and 38 are constructed to achieve a relatively low average reflectance in the visible spectrum. For example, in embodiments, the window comprises an average reflectance, computed in a wavelength range from 400 nm to 700 nm, of less than or equal to 10% (e.g., less than or equal to 9%, less than or equal to 8%, less than or equal to 7%). Such low reflectance beneficially prevents the window 24 from having a tinted appearance when viewed from the external environment 26 (see FIG. 1) and facilitates achieving the CIE color space a* and b*, and lightness L* values described herein.

[00134] In embodiments, to limit the reflectance in the visible spectrum of the window, a silicon layer of the second layered film 38 most proximate to the substrate 30 is the narrowest silicon layer in the second layered film 38. That is, of the layers in the second layered film 38 where the one or more higher refractive index materials 40 is silicon, the closest one to the substrate 30 comprises the least thickness. In embodiments, the nearest silicon layer in the second layered film 38 comprises a thickness that is less than or equal to 10 nm (e.g., less than or equal to 8 nm, less than or equal to 7 nm, less than or equal to 6 nm, less than or equal to 5 nm, less than or equal to 4 nm, less than or equal to 3 nm, less than or equal to 2 nm). Applicant has found that such structure beneficially prevents the silicon-containing layers in the second layered film 38 from inducing a tinted reflectance, while still contributing to the relatively low visible transmittance values described herein.

[00135] In embodiments, the layer of the one or more higher refractive index materials 40 that is closest to the substrate 30 in the second layered film 38 is not silicon. In embodiments, for example, the layer of the one or more higher refractive index materials 40 that is closest to the substrate 30 may be constructed of the same higher refractive index material used in the first layered film (e.g., SiN _x , SiOxNy, SislSfi). In embodiments, the layer of the one or more higher refractive index materials 40 that is closest to the substrate 30 in the second layered film 38 is the only higher index layer therein that is not constructed of silicon. Without wishing to be bound by theory, Applicant believes that such a structure may aid in reducing reflectance in the visible spectrum when incorporating silicon into the second layered film 38, especially when the silicon layers contained in the second layered film 38 comprise thicknesses greater than or equal to 8 nm. [00136] The layers of the first layered film 36 and the second layered film 38 (i.e., layers of the higher refractive index material 40 and the lower refractive index material 42) may be formed by any known method in the art, including discrete deposition or continuous deposition processes. In one or more embodiments, the layer may be formed using only continuous deposition processes, or, alternatively, only discrete deposition processes.

Examples

[00137] The following examples are all modeled examples using computer facilitated modeling to demonstrate how the quantity, thicknesses, number, and materials of the layers of the first layered film 36 and the second layered film 38 can be configured so that the window 24 has a desired average percentage transmittance and average percentage reflectance as a function of the wavelength and angle of incidence of the incident electromagnetic radiation.

[00138] The refractive indices of the materials in each of the materials and extinction coefficients were measured as a function of wavelength throughout the spectral range of 400 nm to 1600 nm. The refractive indices and optical absorbance for SiO _x N _y , SiN _x , SiCh, Si, and an aluminosilicate glass substrate (Corning code 2320) are provided in the Table A below. Those materials are utilized in some of following examples as the higher refractive index materials 40, the lower refractive index materials 42, and the substrate 30.

TABLE A

SiO _x N _y SiN _x (1)

Wavelength (nm) n k Wavelength (nm) n k

250.08 2.2916 0.03163 250.24 2.39286 0.05616

299.12 2.16039 0.00918 299.48 2.24497 0.01248

351.35 2.09475 0.00372 350.31 2.16478 0.00309

400.41 2.06074 0.00255 399.52 2.12156 0.00113

449.46 2.03937 0.00178 450.3 2.09372 0.00047

500.06 2.0243 0.00107 499.45 2.07562 0.00023

550.61 2.01331 0.00054 550.14 2.06238 0.00012

599.52 2.00526 0.00027 600.76 2.05268 0.00007

649.92 1.99882 0.00013 649.74 2.04553 0.00004

700.23 1.99373 0.00006 700.22 2.03978 0.00003

750.42 1.98962 0.00003 750.6 2.03523 0.00002

850.4 1.98335 0.00001 849.48 2.02863 0.00001

949.72 1.97874 0 949.45 2.02401 0.00001

1051.34 1.97502 0 1049.51 2.02068 0

1149.25 1.97203 0 1151.64 2.01816 0

1251.12 1.96931 0 1250.69 2.01629 0

1350.16 1.96691 0 1350.06 2.01482 0

1449.76 1.96465 0 1449.74 2.01365 0

TABLE A - continued

TABLE A - continued

[00139] These refractive indices were then used to calculate transmission and reflectance spectra. The modeled examples use a single refractive index value in their descriptive tables for convenience, which corresponds to a point selected from the refractive index dispersion curves at about 1550nm wavelength.

[00140] Example 1 - The window 24 of Example 1 included a first layered film 36 over a first surface 32 of a substrate 30 of an aluminosilicate glass (Coming code 2320). The window 24 also included a second layered film 38 over a second surface 34 of the substrate 30. The first layered film 36 included twenty-five (25) alternating layers of SiCh (the SiChQ) material in Table A above) as the lower refractive index material 42 and SiO _x N _y as the higher refractive index material 40. Layer 18 was the scratch resistant layer of the higher refractive index material 40, having a thickness of 2000 nm. Layers 1-17 were optical control layers having a combined thickness of 1398.6 nm separating the scratch resistant layer from the terminal surface 44. Layers 18-25 were index matching layers separating the scratch resistance layer from the first surface 32 and having a combined thickness of 252.1 nm. In this example, the scratch resistant layer constituted 54.78% of the thickness of the first layered film 36.

[00141] The second layered film 38 included fifteen (15) alternating layers of the lower refractive index material 42 and the higher refractive index material 40. In this example, the lower refractive index material 42 was SiCh, while the higher refractive index material 40 was a combination of SiO _x N _y and Si . As shown, layer 28 - the layer of the higher refractive index material 40 most proximate to the substrate 30 (layer 26 in this example) - was SiO _x N _y , while the remaining layers of the higher refractive index material 40 were Si. Layer 30 - the Si layer most proximate to the substrate 30 - was the narrowest Si layer, with a thickness of 8.1 nm. The combined thickness of the silicon layers was 595 nm, which constituted 46.2% of the total thickness of the second layered film 38.

[00142] The refractive index and extinction coefficient values of the Si material used in Example 1 are shown in FIG. 6. As shown, the extinction coefficient of the Si material used in this example is 0.23 at 700 nm, which corresponds to approximately 1.37% internal transmittance (for just the silicon) for the combined thickness of the silicon layers in Example 1. At 400 nm, the extinction coefficient is 2.2. As a result, the transmittance of the combined silicon layers is expected to much lower at 400 nm than it is at 700 nm.

[00143] The thicknesses of the layers of the first layered film 36 and the second layered film 38 were configured as set forth in Table 1 below and used to calculate the transmittance, reflectance, CIELAB color space and lightness values, and nanoindentation hardness values set forth in FIGS. 7-13.

TABLE 1

Example 1 Layer Design

_T n j • i Refractive Index Physical Thickness

Layer Material

(a>I550nm ( _z nm _x )

Medium Air 1

Perfluoropolyether 1-4 4-8

1 SiO ₂ 1.45243 122.0

2 SiO _x N _y 1.96247 29.3

3 SiO ₂ 1.45243 70.7

4 SiOxN _y 1.96247 23.2

5 SiO ₂ 1.45243 60.3

6 SiOxNy 1.96247 151.5

7 SiO ₂ 1.45243 51.9

8 SiOxNy 1.96247 31.4

9 SiO ₂ 1.45243 55.5

10 SiOxNy 1.96247 25.6 11 SiO ₂ 1.45243 198.6

12 SiOxNy 1.96247 120.4

13 SiO ₂ 1.45243 170.9

14 SiOxNy 1.96247 129.4

15 SiO ₂ 1.45243 87.6

16 SiOxNy 1.96247 10.3

17 SiO ₂ 1.45243 60.0

18 SiOxNy 1.96247 2000

19 SiO ₂ 1.45243 26.3

20 SiOxNy 1.96247 39.2

21 SiO ₂ 1.45243 45.9

22 SiOxNy 1.96247 33.6

23 SiO ₂ 1.45243 61.1

24 SiOxNy 1.96247 21.1

25 SiO ₂ 1.45243 25.0

Substrate Aluminosilicate glass (2320) 1.4916 2000000.0

27 SiO ₂ 1.45243 25.0

28 SiOxNy 1.96247 46.1

29 SiO ₂ 1.45243 12.8

30 Si 3.77682 8.1

31 SiO ₂ 1.45243 28.1

32 Si 3.77682 21.6

33 SiO ₂ 1.45243 8.0

34 Si 3.77682 200.7

35 SiO ₂ 1.45243 28.8

36 Si 3.77682 161.9

37 SiO ₂ 1.45243 146.1

38 Si 3.77682 18.0

39 SiO ₂ 1.45243 167.8

40 Si 3.77682 184.7

41 SiO ₂ 1.45243 231.1 Medium Air 1

[00144] FIG. 7 depicts a plot including a first curve 702 showing a modelled transmittance of the window 24 according to Example 1 of light normally incident on the window 24 throughout the spectral range of 400 nm to 1600 nm, a second curve 704 showing a modelled reflectance of light normally incident on the second layered film 38 throughout the spectral range of 400 nm to 1600 nm, and a third curve 706 showing a modelled reflectance of light normally incident on the first layered film 36 throughout the spectral range of 400 nm to 1600 nm. As shown, the quantity, thicknesses, number, and materials of the first layered film 36 and the second layered film 38 have been configured so that the window 24 of Example 1 so that light normally incident on the window 24 above wavelengths of 1420 nm has a transmittance of greater than 90%. Throughout the visible spectrum, the transmittance is less than 2%. As shown in the curves 704 and 706, whether viewed from the first layered film 36 or the second layered film 38, the window 24 according to Example 1 has a reflectance of less than 1% for wavelengths above 1500 nm. Throughout the visible spectrum, when viewed from the first layered film 36, the window according to Example 1 has a reflectance of less than 9%. As such, the results in FIG. 7 demonstrate that the efficacy of the window 24 according to Example 1 providing effective antireflection performance in the infrared wavelengths described herein, while effectively preventing transmission and reflectance in the visible spectrum.

[00145] As revealed in FIG. 8, the quantity, thicknesses, number, and materials of the first layered film 36 and the second layered film 38 have been configured so that the window 24 of Example 1 has a percentage transmittance of above 92.25 percent for light normally incident on the first surface 32 or the second surface 34 throughout a wavelength range extending from 1500 nm to 1600 nm. As revealed in FIG. 9, the quantity, thicknesses, number, and materials of the first layered film 36 and the second layered film 38 have been configured so that the window 24 of Example 1 has an average P polarization transmittance and an average S polarization transmittance, calculated a wavelength range of interest from 1500 nm to 1600 nm, of greater than 87% for light incident on the first surface and the second surface at angles within 60° of normal to the first surface and the second surface.

[00146] As revealed in FIG. 10, the quantity, thicknesses, number, and materials of the first layered film 36 and the second layered film 38 have been configured so that the window 24 of Example 1 has a percentage reflectance off of the terminal surface 44 of the first layered film 36 and the terminal surface 48 of the second layered film 38 of under 0.8 percent for light normally incident on the substrate 300 within the approximate wavelength range of 1500 nm to 1600 nm. The reflectance from the terminal surface 44 is comparable to that from the terminal surface 48, as the first and second layered films 36 and 38 were constructed of materials having relatively low absorbance in the referenced wavelength range. As shown, the modelled reflectance reaches a minimum value of approximately 0.1% at about 1550 nm, and the reflectance is less than 0.25% throughout the wavelength range of 1525 nm to 1575 nm.

[00147] As revealed in FIG. 11, the quantity, thicknesses, number, and materials of the first layered film 36 and the second layered film 38 have been configured so that the window 24 of Example 1 has a transmittance substantially less than 1.0% throughout the visible spectrum. From 400 nm to 650 nm, the transmittance in the visible spectrum is less than 0.2%. For wavelengths less than 600 nm, the transmittance in the visible spectrum is less than 0.1%. It is believed that these low transmission values are due in part to the absorbance of visible light by the silicon layers in the second layered film 38.

[00148] As revealed in FIGS. 12 A and 12B, the quantity, thicknesses, number, and materials of the first layered film 36 and the second layered film 38 have been configured so that the window 24 of Example 1 has a dark appearance when viewed from the terminal surface 44 of the first layered film. As shown in FIG. 12A provides simulated CIELAB single-surface reflected color data for Example 1 for light reflected off of the terminal surface 44. The color of the single-surface reflected light can be characterized using CIELAB color coordinates. The a* axis in color space is representative of the green-red color component, with negative a* values corresponding to green and positive a* values corresponding to red. The b* axis in color space is representative of the blue-yellow component, with negative b* values corresponding to blue and positive b* values corresponding to yellow. The closer the a* and b* values are to the origin, the more neutral in color the reflected light will appear to an observer. The CIELAB a* and b* values were generated by simulating an illuminant source at a plurality of different angles of incidence, ranging from 0° to 90°. As shown, the a* values ranges from about -2.25 to about 0.4, while the b* values ranges from about -2.2 to about 1.25. This indicates that the window 24 according to example 1 has a neutral appearance when viewed form the external environment 26 (see FIG. 1).

[00149] FIG. 12B depicts modelled CIELAB lightness L* values as a function of angle of incidence on the terminal surface 44. As shown, for angles of incidence less than or equal to 60°, the lightness L* value is less than or equal to 30. This indicates that the window 24 according to example 1 has a dark appearance when viewed form the external environment 26 (see FIG. 1).

[00150] FIG. 13 reveals nanoindentation hardness measured as a function of depth for two samples constructed in accordance with Example 1 herein. The hardness values were simulated as being subjected to the Berkovich Indenter Hardness Test described herein. The first sample was measured for a range of depths form 50 nm to 1000 nm, while the second sample was measured for a range of depths from 50 nm to 2000nm. As depicted in FIG. 11, both samples exhibited a first maximum hardness 1104 at approximately 250 nm in depth of greater than 8 GPa. The second sample also exhibited a second maximum hardness 1102 of greater than 10 GPA at approximately 1050 nm in depth. Without wishing to be bound by theory, it is believed that the maximum hardness lies above the scratch resistant layers due to the stress fields caused by the indenter propagating beneath the scratch resistant layer once the depth reaches 1050 nm. As demonstrated by FIG. 11, the window 24 according to Example 1 exhibits a nanoindentation hardness of greater than 8 GPa throughout a depth range of 250 nm to 2000 nm. The window 24 according to Example 1 also exhibits a nanoindentation hardness of greater than 9 GPa throughout a depth range of 750 nm to 2000 nm. This indicates that this example provides favorable scratch/damage resistance for various applications.

[00151] Example 2 - The window 24 of Example 2 included a first layered film 36 over a first surface 32 of a substrate 30 of an aluminosilicate glass (Coming code 2320). The window 24 also included a second layered film 38 over a second surface 34 of the substrate 30. The first layered film 36 included twenty-one (21) alternating layers of SiCh (the SiCh (2) material of Table A) as the lower refractive index material 42 and SiN _x (the SiN _x (l) material of Table A) as the higher refractive index material 40. Layer 14 was the scratch resistant layer of the higher refractive index material 40, having a thickness of 2000 nm and constructed of the SiN _x (2) material of Table A. Layers 1-13 were optical control layers having a combined thickness of 1063.9 nm separating the scratch resistant layer from the terminal surface 44. Layers 15-21 were index matching layers separating the scratch resistance layer from the first surface 32 and having a combined thickness of 241.8 nm. In this example, the scratch resistant layer constituted 60.5 % of the thickness of the first layered film 36.

[00152] The second layered film 38 included thirteen (13) alternating layers of the lower refractive index material 42 and the higher refractive index material 40. In this example, the lower refractive index material 42 was SiCh (the SiCh (2) material of Table A), while the higher refractive index material 40 was a combination of SiN _x (the SiN _x (l) material of Table A) and Si. As shown, layer 24 - the layer of the higher refractive index material 40 most proximate to the substrate 30 (layer 20 in this example) - was SiN _x , while the remaining layers of the higher refractive index material 40 were Si. Layer 26 - the Si layer most proximate to the substrate 30 - was the narrowest Si layer, with a thickness of 8.0 nm. The combined thickness of the silicon layers was 414.6 nm, which constituted 39.49% of the total thickness of the second layered film 38.

[00153] The refractive index and extinction coefficient values of the Si material used in Example 2 are shown in FIG. 14. As shown, the extinction coefficient of the Si material used in this example is 0.29 at 700 nm, which corresponds to approximately 2.29% internal transmittance (for just the silicon) for the combined thickness of the silicon layers in Example 2. At 400 nm, the extinction coefficient is 2.2. As a result, the transmittance of the combined silicon layers is expected to be much lower at 400 nm than it is at 700 nm.

[00154] The thicknesses of the layers of the first layered film 36 and the second layered film 38 were configured as set forth in Table 2 below and used to calculate the transmittance, reflectance, CIELAB color space and lightness values, and nanoindentation hardness set forth in FIGS. 15-20B.

TABLE 2

Example 2 Layer Design

, . , . , Refractive Index Physical Thickness

Lay yer Material @1550nm (nm)

Medium Air 1

Perfluoropolyether 1-4 4-8

1 SiO ₂ 1.46349 306.6

2 SiN _x 2.01269 16.9

3 SiO ₂ 1.46349 21.7

4 SiNx 2.01269 106.5

5 SiO ₂ 1.46349 31.6

6 SiNx 2.01269 14.1

7 SiO ₂ 1.46349 467.8

8 SiNx 2.01269 8.1

9 SiO ₂ 1.46349 66.8

10 SiNx 2.01269 23.9

11 SiO ₂ 1.46349 36.4

12 SiNx 2.01269 39.1

13 SiO ₂ 1.46349 11.2

14 SiNx 1.98699 2000

15 SiO ₂ 1.46349 22.1

16 SiNx 2.01269 39.6

17 SiO ₂ 1.46349 44.2

18 SiNx 2.01269 39.1

19 SiO ₂ 1.46349 50.6

20 SiNx 2.01269 21.2

21 SiO ₂ 1.46349 25.0

Substrate Aluminosilicate glass (2320) 1.4916 2000000.0

23 SiO ₂ 1.46349 25.0

24 SiNx 2.01269 49.0

25 SiO ₂ 1.46349 12.9

26 Si 3.84504 8.0

T1 SiO ₂ 1.46349 35.6

28 Si 3.84504 18.5

29 SiO ₂ 1.46349 22.6

30 Si 3.84504 162.4

31 SiO ₂ 1.46349 98.9

32 Si 3.84504 26.6

33 SiO ₂ 1.46349 117.7

34 Si 3.84504 199.1 35 SiO ₂ 1.46349 273.5

Medium Air 1

[00155] FIG. 15 depicts a plot including a first curve 1502 showing a modelled transmittance of the window 24 according to Example 2 of light normally incident on the window 24 throughout the spectral range of 400 nm to 1600 nm, a second curve 1504 showing a modelled reflectance of light normally incident on the first layered film 36 throughout the spectral range of 400 nm to 1600 nm, and a third curve 1506 showing a modelled reflectance of light normally incident on the second layered film 38 throughout the spectral range of 400 nm to 1600 nm. As shown, the quantity, thicknesses, number, and materials of the first layered film 36 and the second layered film 38 have been configured so that light normally incident on the window 24 above wavelengths of 1380 nm has a transmittance of greater than 90%. Throughout the visible spectrum, the transmittance is less than 2%. As shown in the curves 1504 and 1506, whether viewed from the first layered film 36 or the second layered film 38, the window 24 according to Example 2 has a reflectance of less than 1% for wavelengths above 1500 nm. Throughout the visible spectrum, when viewed from the first layered film 36, the window according to Example 2 has a reflectance of less than 22%. As such, the results in FIG. 15 demonstrate that the efficacy of the window 24 according to Example 2 providing effective antireflection performance in the infrared wavelengths described herein, while effectively preventing transmission and reflectance in the visible spectrum.

[00156] As revealed in FIG. 16, the quantity, thicknesses, number, and materials of the first layered film 36 and the second layered film 38 have been configured so that the window 24 of Example 2 has a percentage transmittance of above 99.6 percent for light normally incident on the first surface 32 or the second surface 34 throughout a wavelength range extending from 1500 nm to 1600 nm. As revealed in FIG. 17, the quantity, thicknesses, number, and materials of the first layered film 36 and the second layered film 38 have been configured so that the window 24 of Example 2 has an average P polarization transmittance and an average S polarization transmittance, calculated a wavelength range of interest from 1500 nm to 1600 nm, of greater than 91.75% for light incident on the first surface and the second surface at angles within 60° of normal to the first surface and the second surface.

[00157] As revealed in FIG. 18, the quantity, thicknesses, number, and materials of the first layered film 36 and the second layered film 38 have been configured so that the window 24 of Example 2 has a percentage reflectance from the terminal surface 44 (and each of the layers in the window 24) of the first layered film 36 and the terminal surface 48 of the second layered film 38 of under 0.4 percent for light normally incident on the substrate 300 within the approximate wavelength range of 1500 nm to 1600 nm. The reflectance from the terminal surface 44 is comparable to that from the terminal surface 48, as the first and second layered films 36 and 38 were constructed of materials having relatively low absorbance in the referenced wavelength range. As shown, the modelled reflectance reaches a minimum value of approximately 0.1% at about 1550 nm, and the reflectance is less than 0.25% throughout the wavelength range of 1510 nm to 1600 nm.

[00158] As revealed in FIG. 19, the quantity, thicknesses, number, and materials of the first layered film 36 and the second layered film 38 have been configured so that the window 24 of Example 2 has a transmittance substantially less than 1.0% throughout the visible spectrum. From 400 nm to 650 nm, the transmittance in the visible spectrum is less than 0.2%. For wavelengths less than 550 nm, the transmittance in the visible spectrum is less than 0.1%. It is believed that these low transmission values are due at least in part to the absorbance of visible light by the silicon layers in the second layered film 38.

[00159] As revealed in FIGS. 20 A and 20B, the quantity, thicknesses, number, and materials of the first layered film 36 and the second layered film 38 have been configured so that the window 24 of Example 2 has a dark appearance when viewed from the terminal surface 44 of the first layered film. FIG. 20A provides simulated CIELAB single-surface reflected color data for Example 2 for light reflected off of the terminal surface 44. The color of the single-surface reflected light can be characterized using CIELAB color coordinates. The a* axis in color space is representative of the green-red color component, with negative a* values corresponding to green and positive a* values corresponding to red. The b* axis in color space is representative of the blue-yellow component, with negative b* values corresponding to blue and positive b* values corresponding to yellow. The closer the a* and b* values are to the origin, the more neutral in color the reflected light will appear to an observer. The CIELAB a* and b* values were generated by simulating an illuminant source at a plurality of different angles of incidence, ranging from 0° to 90°. As shown, the a* values ranges from about -2.0 to about 0.75, while the b* values ranges from about -2.1 to about 1.3. This indicates that the window 24 according to Example 2 has a neutral appearance when viewed form the external environment 26 (see FIG. 1). [00160] FIG. 20B depicts modelled CIELAB lightness L* values as a function of angle of incidence on the terminal surface 44. As shown, for angles of incidence less than or equal to 60°, the lightness L* value is less than or equal to 35. This indicates that the window 24 according to Example 2 has a dark appearance when viewed form the external environment 26 (see FIG. 1).

[00161] Example 3 - The window 24 of Example 3 included a first layered film 36 over a first surface 32 of a substrate 30 of an aluminosilicate glass (Corning code 2320). The window 24 also included a second layered film 38 over a second surface 34 of the substrate 30. The first layered film 36 included twenty-five (25) alternating layers of SiCh as the lower refractive index material 42 (the SiCh (1) material of Table A) and SiN _x as the higher refractive index material 40 (of the SiN _x (l) material of Table A). Layer 18 was the scratch resistant layer of the higher refractive index material 40 (of the SiN _x (2) material of Table A), having a thickness of 2000 nm. Layers 1-17 were optical control layers having a combined thickness of 1387.5 nm separating the scratch resistant layer from the terminal surface 44. Layers 19-25 were index matching layers separating the scratch resistance layer from the first surface 32 and having a combined thickness of 249.5 nm. In this example, the scratch resistant layer constituted 54.99% of the thickness of the first layered film 36.

[00162] The second layered film 38 included fifteen (15) alternating layers of the lower refractive index material 42 and the higher refractive index material 40. In this example, the lower refractive index material 42 was SiCh (the SiCh (2) material of Table A), while the higher refractive index material 40 was a combination of SiN _x (the SiN _x (l) material of Table A) and Si. As shown, layer 28 - the layer of the higher refractive index material 40 most proximate to the substrate 30 (layer 20 in this example) - was SiN _x , while the remaining layers of the higher refractive index material 40 were Si. Layer 30 - the Si layer most proximate to the substrate 30 - was the narrowest Si layer, with a thickness of 8.0 nm. The combined thickness of the silicon layers was 584.28 nm, which constituted 46.62 % of the total thickness of the second layered film 38. The silicon material used in Example 3 was the same as that described above with respect to Example 2 (having the properties depicted in FIG. 14).

[00163] The thicknesses of the layers of the first layered film 36 and the second layered film 38 were configured as set forth in Table 3 below and used to calculate the transmittance, reflectance, CIELAB color space and lightness values, and nanoindentation hardness set forth in FIGS. 21-26B. TABLE 3

Example 3 Layer Design

, . , . , Refractive Index Physical Thickness

Lay yer Material @1550nm (nm)

Medium Air 1

Perfluoropolyether 1-4 4-8

1 SiO ₂ 1.46349 119.78

2 SiN _x 2.01269 29.73

3 SiO ₂ 1.46349 69.16

4 SiNx 2.01269 22.78

5 SiO ₂ 1.46349 60.32

6 SiNx 2.01269 150.89

7 SiO ₂ 1.46349 48.89

8 SiNx 2.01269 31.45

9 SiO ₂ 1.46349 55.68

10 SiNx 2.01269 22.98

11 SiO ₂ 1.46349 200.38

12 SiNx 2.01269 118.3

13 SiO ₂ 1.46349 172.06

14 SiNx 2.01269 128.14

15 SiO ₂ 1.46349 88.63

16 SiNx 2.01269 8.99

17 SiO ₂ 1.46349 59.38

18 SiNx 1.98699 2000

19 SiO ₂ 1.46349 25.22

20 SiNx 2.01269 43.41

21 SiO ₂ 1.46349 44.38

22 SiNx 2.01269 34.4

23 SiO ₂ 1.46349 58.65

24 SiNx 2.01269 18.46

25 SiO ₂ 1.46349 25

Substrate Aluminosilicate glass (2320) 1.4916 2000000.0

T1 SiO ₂ 1.46349 25

28 SiNx 2.01269 43.96

29 SiO ₂ 1.46349 12.55

30 Si 3.84504 8

31 SiO ₂ 1.46349 27.49

32 Si 3.84504 21.22

33 SiO ₂ 1.46349 8

34 Si 3.84504 193.55

35 SiO ₂ 1.46349 28.84

36 Si 3.84504 163.81

37 SiO ₂ 1.46349 139.55

38 Si 3.84504 18.01

39 SiO ₂ 1.46349 159.99

40 Si 3.84504 179.69

41 SiO ₂ 1.46349 223.72

Medium Air 1 [00164] FIG. 21 depicts a plot including a first curve 2102 showing a modelled transmittance of the window 24 according to Example 3 of light normally incident on the window 24 throughout the spectral range of 400 nm to 1600 nm, a second curve 2104 showing a modelled reflectance of light normally incident on the first layered film 36 throughout the spectral range of 400 nm to 1600 nm, and a third curve 2106 showing a modelled reflectance of light normally incident on the second layered film 38 throughout the spectral range of 400 nm to 1600 nm. As shown, the quantity, thicknesses, number, and materials of the first layered film 36 and the second layered film 38 have been configured so that light normally incident on the window 24 above wavelengths of 1420 nm has a transmittance of greater than 90%. Throughout the visible spectrum, the transmittance is less than 2%. As shown in the curves 2104 and 2106, whether viewed from the first layered film 36 or the second layered film 38, the window 24 according to Example 3 has a reflectance of less than 1% for wavelengths above 1500 nm. Throughout the visible spectrum, when viewed from the first layered film 36, the window according to Example 3 has a reflectance of less than 10%. As such, the results in FIG. 21 demonstrate that the efficacy of the window 24 according to Example 3 providing effective antireflection performance in the infrared wavelengths described herein, while effectively preventing transmission and reflectance in the visible spectrum.

[00165] As revealed in FIG. 22, the quantity, thicknesses, number, and materials of the first layered film 36 and the second layered film 38 have been configured so that the window 24 of Example 3 has a percentage transmittance of above 99.0 percent for light normally incident on the first surface 32 or the second surface 34 throughout a wavelength range extending from 1500 nm to 1600 nm. As revealed in FIG. 23, the quantity, thicknesses, number, and materials of the first layered film 36 and the second layered film 38 have been configured so that the window 24 of Example 3 has an average P polarization transmittance and an average S polarization transmittance, calculated a wavelength range of interest from 1500 nm to 1600 nm, of greater than 88% for light incident on the first surface and the second surface at angles within 60° of normal to the first surface and the second surface.

[00166] As revealed in FIG. 24, the quantity, thicknesses, number, and materials of the first layered film 36 and the second layered film 38 have been configured so that the window 24 of Example 3 has a percentage reflectance from the terminal surface 44 (and each of the layers in the window 24) of the first layered film 36 and the terminal surface 48 of the second layered film 38 of under 1.0 percent for light normally incident on the substrate 300 within the approximate wavelength range of 1500 nm to 1600 nm. The reflectance from the terminal surface 44 is comparable to that from the terminal surface 48, as the first and second layered films 36 and 38 were constructed of materials having relatively low absorbance in the referenced wavelength range. As shown, the modelled reflectance reaches a minimum value of approximately 0.1% at about 1540 nm, and the reflectance is less than 0.2% throughout the wavelength range of 1530 nm to 1600 nm.

[00167] As revealed in FIG. 25, the quantity, thicknesses, number, and materials of the first layered film 36 and the second layered film 38 have been configured so that the window 24 of Example 3 has a transmittance substantially less than 0.5% throughout the visible spectrum. From 400 nm to 600 nm, the transmittance in the visible spectrum is less than 0.1%. It is believed that these low transmission values are due in part to the absorbance of visible light by the silicon layers in the second layered film 38.

[00168] As revealed in FIGS. 26 A and 26B, the quantity, thicknesses, number, and materials of the first layered film 36 and the second layered film 38 have been configured so that the window 24 of Example 3 has a dark appearance when viewed from the terminal surface 44 of the first layered film. FIG. 26A provides simulated CIELAB single-surface reflected color data for Example 3 for light reflected off of the terminal surface 44. The color of the single-surface reflected light can be characterized using CIELAB color coordinates. The a* axis in color space is representative of the green-red color component, with negative a* values corresponding to green and positive a* values corresponding to red. The b* axis in color space is representative of the blue-yellow component, with negative b* values corresponding to blue and positive b* values corresponding to yellow. The closer the a* and b* values are to the origin, the more neutral in color the reflected light will appear to an observer. The CIELAB a* and b* values were generated by simulating an illuminant source at a plurality of different angles of incidence, ranging from 0° to 90°. As shown in the curve 2602, the a* values ranges from about -2.25 to about 0.4, while the b* values ranges from about -2.0 to about 0.5. This indicates that the window 24 according to Example 3 has a neutral appearance when viewed form the external environment 26 (see FIG. 1).

[00169] FIG. 26B depicts modelled CIELAB lightness L* values as a function of angle of incidence on the terminal surface 44. As shown, for angles of incidence less than or equal to 60°, the lightness L* value is less than or equal to 30. This indicates that the window 24 according to Example 3 has a dark appearance when viewed form the external environment 26 (see FIG. 1). [00170] Example 4 - The window 24 of Example 4 included a first layered film 36 over a first surface 32 of a substrate 30 of an aluminosilicate glass (Coming code 2320). The window 24 also included a second layered film 38 over a second surface 34 of the substrate 30. The first layered film 36 included twenty-nine (29) alternating layers of SiCh as the lower refractive index material 42 (the SiO2(2) material of Table A) and SiN _x as the higher refractive index material 40 (the SiN _x (l) material of Table A) . Layer 20 was the scratch resistant layer of the higher refractive index material 40 (of the SiN _x (2) material of Table A), having a thickness of 2000 nm. Layers 1-19 were optical control layers having a combined thickness of 1361.8 nm separating the scratch resistant layer from the terminal surface 44. Layers 21-29 were index matching layers separating the scratch resistance layer from the first surface 32 and having a combined thickness of 326.0 nm. In this example, the scratch resistant layer constituted 54.23% of the thickness of the first layered film 36.

[00171] The second layered film 38 included fifteen (15) alternating layers of the lower refractive index material 42 and the higher refractive index material 40. In this example, the lower refractive index material 42 was SiCh (the SiC>2(2) material of Table A), while the higher refractive index material 40 was a combination of SiN _x (the SiN _x (l) material of table A) and Si. As shown, layer 32 - the layer of the higher refractive index material 40 most proximate to the substrate 30 (layer 20 in this example) - was SiN _x , while the remaining layers of the higher refractive index material 40 were Si. Layer 34 - the Si layer most proximate to the substrate 30 - was the narrowest Si layer, with a thickness of 8.23 nm. The combined thickness of the silicon layers was 585 nm, which constituted 45.41 % of the total thickness of the second layered film 38. The silicon material used in Example 4 was the same as that described above with respect to Example 2 (having the properties depicted in FIG. 14).

[00172] The thicknesses of the layers of the first layered film 36 and the second layered film 38 were configured as set forth in Table 4 below and used to calculate the transmittance, reflectance, CIELAB color space and lightness values, and nanoindentation hardness set forth in FIGS. 27-32B. TABLE 4

Example 4 Layer Design

, . , . , Refractive Index Physical Thickness

Lay yer Material @1550nm (nm)

Medium Air 1

Perfluoropolyether 1-4 4-8

1 SiO ₂ 1.46349 255.23

2 SiN _x 2.01269 145.36

3 SiO ₂ 1.46349 45.77

4 SiNx 2.01269 41.32

5 SiO ₂ 1.46349 12.73

6 SiNx 2.01269 81.51

7 SiO ₂ 1.46349 183.2

8 SiNx 2.01269 65.17

9 SiO ₂ 1.46349 8.32

10 SiNx 2.01269 79.42

11 SiO ₂ 1.46349 41.57

12 SiNx 2.01269 45.86

13 SiO ₂ 1.46349 11.7

14 SiNx 2.01269 203.02

15 SiO ₂ 1.46349 22.08

16 SiNx 2.01269 44.73

17 SiO ₂ 1.46349 41.83

18 SiNx 2.01269 28.12

19 SiO ₂ 1.46349 24.82

20 SiNx 1.98699 2000

21 SiO ₂ 1.46349 18.67

22 SiNx 2.01269 43.78

23 SiO ₂ 1.46349 43.08

24 SiNx 2.01269 37.09

25 SiO ₂ 1.46349 50.41

26 SiNx 2.01269 31.2

T1 SiO ₂ 1.46349 61.22

28 SiNx 2.01269 15.53

29 SiO ₂ 1.46349 25

Substrate Aluminosilicate glass (2320) 1.4916 2000000.0

31 SiO ₂ 1.46349 25

32 SiNx 2.01269 58.92

33 SiO ₂ 1.46349 8.1

34 Si 3.84504 8.23

35 SiO ₂ 1.46349 23.85

36 Si 3.84504 22.75

37 SiO ₂ 1.46349 8

38 Si 3.84504 192.06

39 SiO ₂ 1.46349 27.67

40 Si 3.84504 159.83

41 SiO ₂ 1.46349 141.65

42 Si 3.84504 19.03 43 SiO ₂ 1.46349 167.14

44 Si 3.84504 183.1

45 SiO ₂ 1.46349 243.02

Medium Air 1

[00173] FIG. 27 depicts a plot including a first curve 2702 showing a modelled transmittance of the window 24 according to Example 4 of light normally incident on the window 24 throughout the spectral range of 400 nm to 1600 nm, a second curve 2704 showing a modelled reflectance of light normally incident on the first layered film 36 throughout the spectral range of 400 nm to 1600 nm, and a third curve 2706 showing a modelled reflectance of light normally incident on the second layered film 38 throughout the spectral range of 400 nm to 1600 nm. As shown, the quantity, thicknesses, number, and materials of the first layered film 36 and the second layered film 38 have been configured so that light normally incident on the window 24 above wavelengths of 1400 nm has a transmittance of greater than 90%. Throughout the visible spectrum, the transmittance is less than 1%. As shown in the curves 2704 and 2706, whether viewed from the first layered film 36 or the second layered film 38, the window 24 according to Example 4 has a reflectance of less than 1% for wavelengths above 1500 nm. Throughout the visible spectrum, when viewed from the first layered film 36, the window according to Example 4 has a reflectance of less than 22% (with the reflectance being less than 10% for wavelengths greater than about 420 nm). As such, the results in FIG. 27 demonstrate that the efficacy of the window 24 according to Example 4 providing effective antireflection performance in the infrared wavelengths described herein, while effectively preventing transmission and reflectance in the visible spectrum.

[00174] As revealed in FIG. 28, the quantity, thicknesses, number, and materials of the first layered film 36 and the second layered film 38 have been configured so that the window 24 of Example 4 has a percentage transmittance of above 99.4 percent for light normally incident on the first surface 32 or the second surface 34 throughout a wavelength range extending from 1500 nm to 1600 nm. As revealed in FIG. 29, the quantity, thicknesses, number, and materials of the first layered film 36 and the second layered film 38 have been configured so that the window 24 of Example 4 has an average P polarization transmittance and an average S polarization transmittance, calculated a wavelength range of interest from 1500 nm to 1600 nm, of greater than 92.2% for light incident on the first surface and the second surface at angles within 60° of normal to the first surface and the second surface. The S and P polarization transmittances are greater than 93.5% throughout the wavelength range of 1530 nm and 1600 nm. The Example 4 appears to provide the best antireflective performance at high angles of incidence, irrespective of polarization, for all of the examples. [00175] As revealed in FIG. 30, the quantity, thicknesses, number, and materials of the first layered film 36 and the second layered film 38 have been configured so that the window 24 of Example 4 has a percentage reflectance from the terminal surface 44 (and each of the layers in the window 24) of the first layered film 36 and the terminal surface 48 of the second layered film 38 of under 0.6 percent for light normally incident on the substrate 300 within the approximate wavelength range of 1500 nm to 1600 nm. The reflectance from the terminal surface 44 is comparable to that from the terminal surface 48, as the first and second layered films 36 and 38 were constructed of materials having relatively low absorbance in the referenced wavelength range. As shown, the modelled reflectance reaches a minimum value of approximately 0.08% at about 1550 nm, and the reflectance is less than 0.1% throughout the wavelength range of 1535 nm to 1565 nm.

[00176] As revealed in FIG. 31, the quantity, thicknesses, number, and materials of the first layered film 36 and the second layered film 38 have been configured so that the window 24 of Example 4 has a transmittance substantially less than 0.3% throughout the visible spectrum for light normally incident on the substrate 30. From 400 nm to 650 nm, the transmittance in the visible spectrum is less than 0.1%. It is believed that these low transmission values are due to the absorbance of visible light by the silicon layers in the second layered film 38.

[00177] As revealed in FIGS. 32A and 32B, the quantity, thicknesses, number, and materials of the first layered film 36 and the second layered film 38 have been configured so that the window 24 of Example 4 has a dark appearance when viewed from the terminal surface 44 of the first layered film. FIG. 32A provides simulated CIELAB single-surface reflected color data for Example 4 for light reflected off of the terminal surface 44. The color of the single-surface reflected light can be characterized using CIELAB color coordinates. The a* axis in color space is representative of the green-red color component, with negative a* values corresponding to green and positive a* values corresponding to red. The b* axis in color space is representative of the blue-yellow component, with negative b* values corresponding to blue and positive b* values corresponding to yellow. The closer the a* and b* values are to the origin, the more neutral in color the reflected light will appear to an observer. The CIELAB a* and b* values were generated by simulating an illuminant source at a plurality of different angles of incidence, ranging from 0° to 90°. As shown in the curve 3202, the a* values ranges from about -3.15 to about 1.5, while the b* values ranges from about -4.0 to 5.6. This indicates that the window 24 according to Example 4 has a neutral appearance when viewed form the external environment 26 (see FIG. 1).

[00178] FIG. 32B depicts modelled CIELAB lightness L* values as a function of angle of incidence on the terminal surface 44. As shown, for angles of incidence less than or equal to 60°, the lightness L* value is less than or equal to 42. This indicates that the window 24 according to Example 4 has a dark appearance when viewed form the external environment 26 (see FIG. 1).

[00179] Example 5 - The window 24 of Example 5 included a first layered film 36 over a first surface 32 of a substrate 30 of an aluminosilicate glass (Coming code 2320). The window 24 also included a second layered film 38 over a second surface 34 of the substrate 30. The first layered film 36 included twenty-seven (27) alternating layers of SiCh as the lower refractive index material 42 (the SiC>2(2) material of Table A) and SiN _x as the higher refractive index material 40 (the SiN _x (l) material of Table A). Layer 18 was the scratch resistant layer of the higher refractive index material 40 (the SiN _x (2) material of Table A), having a thickness of 2000 nm. Layers 1-17 were optical control layers having a combined thickness of 1300 nm separating the scratch resistant layer from the terminal surface 44. Layers 19-27 were index matching layers separating the scratch resistance layer from the first surface 32 and having a combined thickness of 376.2 nm. In this example, the scratch resistant layer constituted 54.40% of the thickness of the first layered film 36.

[00180] The second layered film 38 included fifteen (15) alternating layers of the lower refractive index material 42 and the higher refractive index material 40. In this example, the lower refractive index material 42 was SiCh (the SiC>2(2) material of Table A), while the higher refractive index material 40 was a combination of SiN _x (the SiN _x (l) material of Table A) and Si. As shown, layer 30 - the layer of the higher refractive index material 40 most proximate to the substrate 30 (layer 20 in this example) - was SiN _x , while the remaining layers of the higher refractive index material 40 were Si. Layer 32 - the Si layer most proximate to the substrate 30 - was the narrowest Si layer, with a thickness of 8.03 nm. The combined thickness of the silicon layers was 518.35 nm, which constituted 36.67% of the total thickness of the second layered film 38. The silicon material used in Example 5 was the same as that described above with respect to Example 2 (having the properties depicted in FIG. 14). [00181] The thicknesses of the layers of the first layered film 36 and the second layered film 38 were configured as set forth in Table 5 below and used to calculate the transmittance, reflectance, CIELAB color space and lightness values, and nanoindentation hardness set forth in FIGS. 33-38B.

TABLE S

Example 5 Layer Design

, . , . , Refractive Index Physical Thickness

Lay yer Material @1550nm (nm)

Medium Air 1

Perfluoropolyether 1-4 4-8

1 SiO ₂ 1.46349 122.94

2 SiN _x 2.01269 12.24

3 SiO ₂ 1.46349 98.87

4 SiNx 2.01269 9.68

5 SiO ₂ 1.46349 41.51

6 SiNx 2.01269 188.3

7 SiO ₂ 1.46349 10.23

8 SiNx 2.01269 51.36

9 SiO ₂ 1.46349 24.97

10 SiNx 2.01269 20.38

11 SiO ₂ 1.46349 149.22

12 SiNx 2.01269 120.78

13 SiO ₂ 1.46349 175.31

14 SiNx 2.01269 134.41

15 SiO ₂ 1.46349 64.11

16 SiNx 2.01269 16.25

17 SiO ₂ 1.46349 59.81

18 SiNx 1.98699 2000

19 SiO ₂ 1.46349 16.83

20 SiNx 2.01269 63.68

21 SiO ₂ 1.46349 42.06

22 SiNx 2.01269 42.8

23 SiO ₂ 1.46349 42.51

24 SiNx 2.01269 28.13

25 SiO ₂ 1.46349 86.42

26 SiNx 2.01269 18.75

T1 SiO ₂ 1.46349 25

Substrate Aluminosilicate glass (2320) 1.4916 2000000.0

29 SiO ₂ 1.46349 25

30 SiNx 2.01269 47.2

31 SiO ₂ 1.46349 11.19

32 Si 3.84504 8.03

33 SiO ₂ 1.46349 34.14

34 Si 3.84504 13.78

35 SiO ₂ 1.46349 26.93

36 Si 3.84504 17.18

37 SiO ₂ 1.46349 19.94 38 Si 3.84504 250.84

39 SiO ₂ 1.46349 40.88

40 Si 3.84504 47.06

41 SiO ₂ 1.46349 482.11

42 Si 3.84504 181.46

43 SiO ₂ 1.46349 207.8

Medium Air 1

[00182] FIG. 33 depicts a plot including a first curve 3302 showing a modelled transmittance of the window 24 according to Example 5 of light normally incident on the window 24 throughout the spectral range of 400 nm to 1600 nm, a second curve 3304 showing a modelled reflectance of light normally incident on the first layered film 36 throughout the spectral range of 400 nm to 1600 nm, and a third curve 3306 showing a modelled reflectance of light normally incident on the second layered film 38 throughout the spectral range of 400 nm to 1600 nm. As shown, the quantity, thicknesses, number, and materials of the first layered film 36 and the second layered film 38 have been configured so that light normally incident on the window 24 above wavelengths of 1400 nm has a transmittance of greater than 90%. Throughout the visible spectrum, the transmittance is less than 5% (with the transmittance being less than 1% for wavelengths from 400 nm to 630 nm). As shown in the curves 3304 and 3306, whether viewed from the first layered film 36 or the second layered film 38, the window 24 according to Example 5 has a reflectance of less than 1% for wavelengths above 1500 nm. Throughout the visible spectrum, when viewed from the first layered film 36, the window according to Example 5 has a reflectance of less than 22%. As such, the results in FIG. 33 demonstrate that the efficacy of the window 24 according to Example 5 providing effective antireflection performance in the infrared wavelengths described herein, while effectively preventing transmission and reflectance in the visible spectrum.

[00183] As revealed in FIG. 34, the quantity, thicknesses, number, and materials of the first layered film 36 and the second layered film 38 have been configured so that the window 24 of Example 5 has a percentage transmittance of above 99.1 percent for light normally incident on the first surface 32 or the second surface 34 throughout a wavelength range extending from 1500 nm to 1600 nm. As revealed in FIG. 35, the quantity, thicknesses, number, and materials of the first layered film 36 and the second layered film 38 have been configured so that the window 24 of Example 5 has an average P polarization transmittance and an average S polarization transmittance, calculated a wavelength range of interest from 1500 nm to 1600 nm, of greater than 91.8% for light incident on the first surface and the second surface at angles within 60° of normal to the first surface and the second surface.

[00184] As revealed in FIG. 36, the quantity, thicknesses, number, and materials of the first layered film 36 and the second layered film 38 have been configured so that the window 24 of Example 5 has a percentage reflectance from the terminal surface 44 (and each of the layers in the window 24) of the first layered film 36 and the terminal surface 48 of the second layered film 38 of under 1.0 percent for light normally incident on the substrate 300 within the approximate wavelength range of 1500 nm to 1600 nm. The reflectance from the terminal surface 44 is comparable to that from the terminal surface 48, as the first and second layered films 36 and 38 were constructed of materials having relatively low absorbance in the referenced wavelength range. As shown, the modelled reflectance reaches a minimum value of less than 0.05% at about 1545 nm, and the reflectance is less than 0.1% throughout the wavelength range of 1530 nm to 1565 nm.

[00185] As revealed in FIG. 37, the quantity, thicknesses, number, and materials of the first layered film 36 and the second layered film 38 have been configured so that the window 24 of Example 5 has a transmittance substantially less than 3% throughout the visible spectrum for light normally incident on the substrate 30. From 400 nm to 650 nm, the transmittance in the visible spectrum is less than 0.3%. It is believed that these low transmission values are due to the absorbance of visible light by the silicon layers in the second layered film 38.

[00186] As revealed in FIGS. 38 A and 38B, the quantity, thicknesses, number, and materials of the first layered film 36 and the second layered film 38 have been configured so that the window 24 of Example 5 has a dark appearance when viewed from the terminal surface 44 of the first layered film. FIG. 38A provides simulated CIELAB single-surface reflected color data for Example 5 for light reflected off of the terminal surface 44. The color of the single-surface reflected light can be characterized using CIELAB color coordinates. The a* axis in color space is representative of the green-red color component, with negative a* values corresponding to green and positive a* values corresponding to red. The b* axis in color space is representative of the blue-yellow component, with negative b* values corresponding to blue and positive b* values corresponding to yellow. The closer the a* and b* values are to the origin, the more neutral in color the reflected light will appear to an observer. The CIELAB a* and b* values were generated by simulating an illuminant source at a plurality of different angles of incidence, ranging from 0° to 90°. As shown in the curve 3802, the a* values ranges from about -3.1 to about 0.5, while the b* values ranges from about -4.5 to 2.6. This indicates that the window 24 according to Example 5 has a neutral appearance when viewed form the external environment 26 (see FIG. 1).

[00187] FIG. 32B depicts modelled CIELAB lightness L* values as a function of angle of incidence on the terminal surface 44. As shown, for angles of incidence less than or equal to 60°, the lightness L* value is less than or equal to 45. This indicates that the window 24 according to Example 5 has a dark appearance when viewed form the external environment

26 (see FIG. 1).

[00188] Example 6 - The window 24 of Example 6 included a first layered film 36 over a first surface 32 of a substrate 30 of an aluminosilicate glass (Coming code 2320). The window 24 also included a second layered film 38 over a second surface 34 of the substrate 30. The first layered film 36 included twenty-seven (27) alternating layers of SiCh as the lower refractive index material 42 and SiN _x as the higher refractive index material 40. Layer 18 was the scratch resistant layer of the higher refractive index material 40, having a thickness of 2000 nm. Layers 1-17 were optical control layers having a combined thickness of 1818.92 nm separating the scratch resistant layer from the terminal surface 44. Layers 19-

27 were index matching layers separating the scratch resistance layer from the first surface 32 and having a combined thickness of 328.77 nm. In this example, the scratch resistant layer constituted 48.21% of the thickness of the first layered film 36.

[00189] The second layered film 38 included nineteen (19) alternating layers of the lower refractive index material 42 and the higher refractive index material 40. In this example, the lower refractive index material 42 was SiCh, while the higher refractive index material 40 was a combination of SiN _x and Si . As shown, layers 30, 32, and 34- the three layers of the higher refractive index material 40 most proximate to the substrate 30 (layer 26 in this example) - were SiN _x , while the remaining layers of the higher refractive index material 40 were Si. Layer 36 - the Si layer most proximate to the substrate 30 - was the narrowest Si layer, with a thickness of 12.02 nm. The combined thickness of the silicon layers was 708.03 nm, which constituted 27.52% of the total thickness of the second layered film 38.

[00190] The refractive index and extinction coefficient values of the Si material used in Example 6 are shown in FIG. 39. As shown, the extinction coefficient of the Si material used in this example is about 0.37 at 700 nm, which corresponds a low internal transmittance (for just the silicon) for the combined thickness of the silicon layers in Example 6. At 400 nm, the extinction coefficient is about 3.2. As a result, the transmittance of the combined silicon layers is expected to particularly low at 400 nm than it is at 700 nm.

[00191] The thicknesses of the layers of the first layered film 36 and the second layered film 38 were configured as set forth in Table 6 below and used to calculate the transmittance, reflectance, and CIELAB color space values set forth in FIGS. 40, 41, and 42.

TABLE 6

Example 6 Layer Design

, . , . , Refractive Index Physical Thickness

Lay yer Material @1550nm (nm)

Medium Air 1

Perfluoropolyether 1-4 4-8

1 SiO ₂ 1.45723 92.78

2 SiN _x 2.04658 148.69

3 SiO ₂ 1.45723 12.12

4 SiNx 2.04658 191.47

5 SiO ₂ 1.45723 19.15

6 SiNx 2.04658 31.76

7 SiO ₂ 1.45723 184.44

8 SiNx 2.04658 143.06

9 SiO ₂ 1.45723 21.15

10 SiNx 2.04658 135.82

11 SiO ₂ 1.45723 170.15

12 SiNx 2.04658 120.48

13 SiO ₂ 1.45723 181.26

14 SiNx 2.04658 122.22

15 SiO ₂ 1.45723 198.01

16 SiNx 2.04658 25.39

17 SiO ₂ 1.45723 20.97

18 SiNx 1.96239 2000.00

19 SiO ₂ 1.45723 13.77

20 SiNx 2.04658 38.47

21 SiO ₂ 1.45723 47.84

22 SiNx 2.04658 27.40

23 SiO ₂ 1.45723 69.47

24 SiNx 2.04658 25.16

25 SiO ₂ 1.45723 66.80

26 SiNx 2.04658 14.86

T1 SiO ₂ 1.45723 25.00

Substrate Aluminosilicate glass (2320) 1.4916 2000000.0

29 SiO2 1.45723 25.00

30 SiN 2.04658 18.76

31 SiO2 1.45723 59.84

32 SiN 2.04658 21.13

33 SiO2 1.45723 89.14

34 SiN 2.04658 45.03

35 SiO2 1.45723 12.17 36 Si 3.67147 12.02

37 SiO2 1.45723 18.01

38 Si 3.67147 175.73

39 SiO2 1.45723 448.09

40 Si 3.67147 170.34

41 SiO2 1.45723 460.06

42 Si 3.67147 209.10

43 SiO2 1.45723 111.64

44 Si 3.67147 88.61

45 SiO2 1.45723 99.67

46 Si 3.67147 52.23

47 SiO2 1.45723 456.20

Medium Air 1

[00192] FIG. 40 depicts a plot including a first curve 4000 showing a modelled transmittance of the window 24 according to Example 6 of light incident on the window 24 throughout the spectral range of 400 nm to 1600 nm at an angle of incidence of 15° (polarizations averaged), a second curve 4002 showing a modelled transmittance of the window 24 throughout the spectral range of 400 nm to 1600 nm at an angle of incidence of 60° (for S-polarized light), and a third curve 4004 showing a modelled transmittance of the window 24 throughout the spectral range of 400 nm to 1600 nm at an angle of incidence of 60° (for P-polarized light). As shown, the quantity, thicknesses, number, and materials of the first layered film 36 and the second layered film 38 have been configured so that light incident on the window 24 in the wavelength range of 1500 nm to 1575 nm and at an angle of incidence of 15° has an average transmittance of greater than 99.5%. Throughout the visible spectrum, the transmittance is less than 5% (with the transmittance being less than 1% for wavelengths from 400 nm to 750 nm). Additionally, as revealed by the curves 4002 and 4004, the quantity, thicknesses, number, and materials of the first layered film 36 and the second layered film 38 have been configured so that the window 24 of Example 6 has an average P polarization transmittance and an average S polarization transmittance, calculated for a wavelength range of interest from 1500 nm to 1575 nm, of greater than 90% for light incident on the first surface and the second surface at angles within 60° of normal to the first surface and the second surface.

[00193] As revealed by a curve 4100 in FIG. 41, the quantity, thicknesses, number, and materials of the first layered film 36 and the second layered film 38 have been configured so that the window 24 of Example 6 has a percentage reflectance from the terminal surface 44 (and each of the layers in the window 24) of the first layered film 36 of under 0.5 percent for light incident on the substrate 30 at an angle of incidence of 15° within the approximate wavelength range of 1500 nm to 1575 nm. As revealed by a curve 4102 in FIG. 41, the quantity, thicknesses, number, and materials of the first layered film 36 and the second layered film 38 have been configured so that the window 24 of Example 6 has a percentage reflectance from the terminal surface 48 (and each of the layers in the window 24) of the second layered film 38 of under 0.5 percent for light incident on the substrate 30 at an angle of incidence of 15° within the approximate wavelength range of 1500 nm to 1575 nm. The reflectance from the terminal surface 44 is comparable to that from the terminal surface 48, as the first and second layered films 36 and 38 were constructed of materials having relatively low absorbance in the referenced wavelength range. As additionally shown the curve 4100 in FIG. 41, the quantity, thicknesses, number, and materials of the first layered film 36 and the second layered film 38 have been configured so that the window 24 of Example 6 has an average transmittance of less than 3% throughout the visible spectrum for light incident on the first layered film 36 at an angle of incidence of 15°. It is believed that these low reflectance values are due to the absorbance of visible light by the silicon layers in the second layered film 38.

[00194] As revealed in FIG 42, the quantity, thicknesses, number, and materials of the first layered film 36 and the second layered film 38 have been configured so that the window 24 of Example 6 has a neutral appearance when viewed from the terminal surface 44 of the first layered film. FIG. 42 provides simulated CIELAB single-surface reflected color data for Example 6 for light reflected off of the terminal surface 44 under a D65 illuminant with a standard 1964 observer (which describes all CIELAB color measurements described herein). The color of the single-surface reflected light can be characterized using CIELAB color coordinates. The a* axis in color space is representative of the green-red color component, with negative a* values corresponding to green and positive a* values corresponding to red. The b* axis in color space is representative of the blue-yellow component, with negative b* values corresponding to blue and positive b* values corresponding to yellow. The closer the a* and b* values are to the origin, the more neutral in color the reflected light will appear to an observer. The CIELAB a* and b* values were generated by simulating a D65 illuminant source at a plurality of different angles of incidence, ranging from 0° to 90°. As shown in the curve 3802, the b* values ranges from about -0.7 to about 1.25, while the a* values ranges from about -1.1 to 3.1. The Example 6 also exhibited L* values of less than or equal to 30.5 throughout the angular range of interest of 0° to 55°. [00195] In Examples 1 - 6, the first layered film 36 included a number of alternating layers of the lower refractive index materials 42 and the higher refractive index materials 40 that varied from 21 layers to 29 layers and thicknesses ranging from 3305.7 nm to 4147.69 nm. The second layered film 38 in each of the examples included a number of alternating layers of the lower refractive index materials 42 and the higher refractive index materials 40 that varied from 13 layers to 19 layers and thicknesses ranging from 1,049.9 nm to 2572.77 nm. In the examples, therefore, the first layered film 36 was more than 1.5 times thicker than the second layered film 38. This may be due to the relatively high refractive index of the silicon layers in the second layered film 38. Combined thicknesses of silicon in each of the second layered films 38 ranged from 414.6 nm to 708 nm. Example 4 - containing the greatest number of layers in the first layered film 36 - appeared to achieve superior antireflective performance irrespective of polarization at high angles of incidence. It should be appreciated that these examples were designed for a particular wavelength range of around 1550 nm and that alternative windows, having differing numbers, quantities, and materials of layers are contemplated and may fall outside of the ranges listed in this paragraph and still fall within the scope of the present disclosure. These examples are not meant to be limiting.

***

[00196] Example 7 - The window 24 of Example 7 included a first layered film 36 over a first surface 32 of a substrate 30 of an aluminosilicate glass (Coming code 2320). The window 24 also included a second layered film 38 over a second surface 34 of the substrate 30. The first layered film 36 included twenty-seven (27) alternating layers of SiCh as the lower refractive index material 42 and SiN _x as the higher refractive index material 40. Layer 18 was the scratch resistant layer of the higher refractive index material 40, having a thickness of 2000 nm. Layers 1-17 were optical control layers having a combined thickness of 1825.13 nm separating the scratch resistant layer from the terminal surface 44. Layers 19- 27 were index matching layers separating the scratch resistance layer from the first surface 32 and having a combined thickness of 314.7 nm. In this example, the scratch resistant layer constituted 48.31% of the thickness of the first layered film 36.

[00197] The second layered film 38 of Example 7 included twenty-five (25) alternating layers of the lower refractive index material 42 and the higher refractive index material 40. In this example, the lower refractive index material 42 was SiCh, while the higher refractive index material 40 was a combination of SiN _x and Si . As shown, layers 30, 32, and 34- the three layers of the higher refractive index material 40 most proximate to the substrate 30 (layer 26 in this example) - were SiN _x , while the remaining layers of the higher refractive index material 40 were Si. Layer 36 - the Si layer most proximate to the substrate 30 - was the narrowest Si layer, with a thickness of 12.03 nm. The combined thickness of the silicon layers was 1199.18 nm, which constituted 43.89% of the total thickness of the second layered film 38.

[00198] The first layered film 36 of Example 7 differed from that in Example 6 in that the scratch resistant layer was formed of a higher-index SiN _x material (having a refractive index of 2.04658 as opposed to 1.96 in Example 6. It is believed that this material posseses a higher hardness and therefore improves scratch resistance over Example 6. The second layered film 38 in Example 7 differed from that in Example 6 in that a lower extinction coefficient silicon was used in the second layered film 38. Rather than the material represented in FIG. 39, the Si-material comprises an extinction coefficient that is less than .05 (e.g., less than .01, less than .005) at 1550 nm. It is believed that use of such a low extinction coefficient material provides a broader bandwidth of high transmission near 1550 nm and renders the system less sensitive to wavelength shifts

[00199] In Example 7, the thicknesses of the layers of the first layered film 36 and the second layered film 38 were configured as set forth in Table 7 below and used to calculate the transmittance, reflectance, and CIELAB color space values set forth in FIGS. 43-49.

TABLE 7

Example 7 Layer Design

, . , . , Refractive Index Physical Thickness

Lay yer Material @1550nm (nm)

Medium Air 1

Perfluoropolyether 1-4 4-8

1 SiO2 1.45723 88.55

2 SiN 2.04658 146.87

3 SiO2 1.45723 10.38

4 SiN 2.04658 190.28

5 SiO2 1.45723 18.30

6 SiN 2.04658 35.57

7 SiO2 1.45723 186.27

8 SiN 2.04658 144.85

9 SiO2 1.45723 25.84

10 SiN 2.04658 141.32

11 SiO2 1.45723 178.34

12 SiN 2.04658 119.35

13 SiO2 1.45723 186.60

14 SiN 2.04658 123.46

15 SiO2 1.45723 183.17 16 SiN 2.04658 25.51

17 SiO2 1.45723 20.47

18 SiN 2.04658 2000.00

19 SiO2 1.45723 27.25

20 SiN 2.04658 30.19

21 SiO2 1.45723 59.41

22 SiN 2.04658 23.71

23 SiO2 1.45723 58.10

24 SiN 2.04658 26.99

25 SiO2 1.45723 50.51

26 SiN 2.04658 13.54

T1 SiO2 1.45723 25.00

Substrate Aluminosilicate glass (2320) 1.4916 2000000.0

29 SiO2 1.45723 25

30 SiN 2.04658 15.85

31 SiO2 1.45723 58.56

32 SiN 2.04658 27.71

33 SiO2 1.45723 56.62

34 SiN 2.04658 58.91

35 SiO2 1.45723 8.06

36 Si 3.47334 12.03

37 SiO2 1.45723 19.98

38 Si 3.47334 231.52

39 SiO2 1.45723 8.15

40 Si 3.47334 101.10

41 SiO2 1.45723 16.55

42 Si 3.47334 81.73

43 SiO2 1.45723 183.54

44 Si 3.47334 250.05

45 SiO2 1.45723 166.42

46 Si 3.47334 109.97

47 SiO2 1.45723 114.51

48 Si 3.47334 47.71

49 SiO2 1.45723 130.54

50 Si 3.47334 176.63

51 SiO2 1.45723 436.72

52 Si 3.47334 188.44

53 SiO2 1.45723 205.41 Medium Air 1

[00200] FIG. 43 is a plot showing a modelled transmittance of the window 24 according to Example 7 for light incident on the window 24 throughout the spectral range of 400 nm to 1600 nm. The plot shows predicted performance for light incident on the window 24 at an angle of incidence of 15° (polarizations averaged) and light incident on the window 24 at an angle of incidence of 60° (for both S and P polarized light). As shown, the quantity, thicknesses, number, and materials of the first layered film 36 and the second layered film 38 have been configured so that light incident on the window 24 in the wavelength range of 1500 nm to 1575 nm and at an angle of incidence of 15° has an average transmittance of greater than 99.5%. Additionally, the quantity, thicknesses, number, and materials of the first layered film 36 and the second layered film 38 have been configured so that the window 24 of Example 6 has an average P polarization transmittance and an average S polarization transmittance, calculated for a wavelength range of interest from 1500 nm to 1575 nm, of greater than 91% for light incident on the first surface and the second surface at angles within 60° of normal to the first surface and the second surface.

[00201] FIG. 44 is a plot showing a modelled reflectance of the window 24 according to Example 7 from both of the terminal surfaces 44 and 48 (e.g., from both internal and external surfaces of the window 24). As revealed by FIG. 44, the quantity, thicknesses, number, and materials of the first layered film 36 and the second layered film 38 have been configured so that the window 24 of Example 7 has a percentage reflectance from the terminal surfaces 44 and 48 (the curves overlap in FIG. 44) of the first layered film 36 and the second layered film 38 of under 0.5 percent for light incident on the substrate 30 at an angle of incidence of 15° within the approximate wavelength range of 1500 nm to 1575 nm. The reflectance from the terminal surface 44 is comparable to that from the terminal surface 48, as the first and second layered films 36 and 38 were constructed of materials having relatively low absorbance in the referenced wavelength range.

[00202] FIG. 45 is a plot showing a modelled transmittance of the window 24 according to Example 7 over the wavelength range of 350 nm to 1600 nm. As shown in FIG. 45, the quantity, thicknesses, number, and materials of the first layered film 36 and the second layered film 38 have been configured so that the window 24 of Example 7 has an average transmittance of less than 5% throughout the visible spectrum for light incident on the first layered film 36 at an angle of incidence of 15° (polarizations averaged). FIG. 46 is a plot showing a modelled reflectance of the window 24 according to Example 7 over the wavelength range of 350 nm to 1600 nm. As shown in FIG. 46, the quantity, thicknesses, number, and materials of the first layered film 36 and the second layered film 38 have been configured so that the window 24 of Example 7 exhibits an average reflectance of less than 5% throughout the visible spectrum for light incident on the first layered film 36 (for light coming from the outside of the window 24) at an angle of incidence of 15° (polarizations average). FIG. 47 is a plot of a modelled two surface transmittance of the window 24 according to Example 7. As shown, he quantity, thicknesses, number, and materials of the first layered film 36 and the second layered film 38 have been configured so that the window 24 of Example 7 exhibits an average transmittance of less than 0.1% over the wavelength range from 400 nm to 650 nm for light having an angle of incidence of 15° on the window 24. Indeed the window 24 exhibits a transmittance of less than 1% throughout the wavelength range from 400 nm to 700 nm (and a transmittance of less than 0.1% throughout the wavelength range from 400 nm to 650 nm).

[00203] As revealed in FIG 48, the quantity, thicknesses, number, and materials of the first layered film 36 and the second layered film 38 have been configured so that the window 24 of Example 7 has a neutral appearance when viewed from the terminal surface 44 of the first layered film. FIG. 48 provides simulated CIELAB single-surface reflected color data for Example 7 for light reflected off of the terminal surface 44 under a D65 illuminant with a standard 1964 observer (which describes all CIELAB color measurements described herein). The color of the single-surface reflected light can be characterized using CIELAB color coordinates. As shown, the b* values ranges from about -1.0 to about 0.6, while the a* values ranges from about -1.5 to 3.6. FIG. 49 provides simulated L* values for light reflected off the terminal surface 44 under a D65 illuminant with a standard 1964 observer. Example 7 also exhibited L* values of less than or equal to 35 throughout the range of angles of incidence of 0° to 60° (and L* values of less than or equal to 25 throughout the range of angles of incidence of 0° to 50°).

[00204] An aspect (1) of the present disclosure pertains to a window for a sensing system comprising: a substrate comprising a first surface and a second surface, the first surface and the second surface being primary surfaces of the substrate; a first layered film disposed on the first surface of the substrate, the first layered film comprising alternating layers of one or more higher refractive index materials and one or more lower refractive index materials, wherein refractive indices of the one or more higher refractive index materials of the first layered film are higher than refractive indices of the one or more lower refractive index materials of the first layered film; a second layered film disposed on the second surface of the substrate, the second layered film comprising alternating layers of one or more higher refractive index materials and one or more lower refractive index materials, wherein refractive indices of the one or more higher refractive index materials of the second layered film are higher than refractive indices of the one or more lower refractive index materials of the second layered film; and a maximum hardness, measured at the first layered film and by the Berkovich Indenter Hardness Test, of at least 8 GPa, wherein the quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films are configured so that the window has: an average percentage transmittance, calculated over a 50 nm wavelength range of interest between 1400 nm and 1600 nm, of greater than 90% for light incident on the first surface and the second surface at angles of incidence of less than or equal to 15°; an average reflectance, calculated over the 50 nm wavelength range of interest between 1400 nm and 1600 nm, of less than 1% for light incident on the first surface and the second surface at angles of less than or equal to 15°; and an average percentage transmission, calculated from 400 nm to 700 nm, of less than 5% for light incident on the first surface and the second surface at angles of incidence of less than or equal to 15°. [00205] An aspect (2) of the present disclosure pertains to a window according to the aspect (1), wherein the quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films are configured so that the window has an average P polarization transmittance and an average S polarization transmittance, calculated over the 50 nm wavelength range of interest between 1400 nm and 1600 nm, of greater than 85% for light incident on the first surface and the second surface at angles of incidence of less than or equal to 60°.

[00206] An aspect (3) of the present disclosure pertains to a window according to the aspect (2), wherein the average P polarization transmittance and the average S polarization transmittance, calculated over the 50 nm wavelength range of interest between 1400 nm and 1600 nm, are greater than 92% for light incident on the first surface and the second surface at angles of incidence of less than or equal to 60°.

[00207] An aspect (4) of the present disclosure pertains to a window according to any of the aspects (l)-(3), wherein the quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films are configured so that the window has a CIELAB L* value of less than or equal to 45 for angles of incidence of less than or equal to 60° on the first layered film.

[00208] An aspect (5) of the present disclosure pertains to a window according to the aspect (4), wherein the CIELAB L* value is less than or equal to 30 for angles of incidence of less than or equal to 60° on the first layered film.

[00209] An aspect (6) of the present disclosure pertains to a window according to any of the aspects (l)-(5), wherein the quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films are configured so that the window has CIELAB a* and b* values of greater than or equal to -6.0 and less than or equal to 6.0 when viewed from a side of the first layered film.

[00210] An aspect (7) of the present disclosure pertains to a window according to any of the aspects (l)-(5), wherein the quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films are configured so that the window has an average reflectance, calculated throughout the visible spectrum, for light normally incident on the first layered film, of less than or equal to 10%.

[00211] An aspect (8) of the present disclosure pertains to a window according to any of the aspects (l)-(7), wherein the quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films are configured so that the window has an average percentage transmittance, calculated over the 50 nm wavelength range of interest between 1400 nm and 1600 nm, of greater than 95% for light normally incident on the first surface and the second surface.

[00212] An aspect (9) of the present disclosure pertains to a window according to any of the aspects (l)-(5), wherein the substrate is a glass substrate.

[00213] An aspect (10) of the present disclosure pertains to a window according to the aspect (9), wherein the substrate has a region contiguous with the first surface that is under compressive stress, and the absolute value of a maximum of the compressive stress is at least 600 MPa.

[00214] An aspect (11) of the present disclosure pertains to a window according to any of the aspects (l)-(10), wherein the substrate has a thickness of between about 100 pm and about 5 mm.

[00215] An aspect (12) of the present disclosure pertains to a window according to any of the aspects (l)-(l 1), wherein the refractive index of the substrate for electromagnetic radiation having a wavelength of 1550nm is from about 1.45 to about 1.55.

[00216] An aspect (13) of the present disclosure pertains to a window according to any of the aspects (1)-(12), wherein the refractive index of the one or more higher refractive index materials is from about 1.7 to about 4.0, and wherein the refractive index of the one or more lower refractive index materials is from about 1.3 to about 1.6.

[00217] An aspect (14) of the present disclosure pertains to a window according to any of the aspects (1)-(13), wherein a difference in the refractive index of any of the one or more higher refractive index materials and any of the one or more lower refractive index materials is about 0.5 or greater. [00218] An aspect (15) of the present disclosure pertains to a window according to any of the aspects ( 1 )-(14), wherein one of the alternating layers of the first layered film that is farthest from the substrate forms a terminal surface material of the window, the terminal surface material of the window comprising the lower refractive index material.

[00219] An aspect (16) of the present disclosure pertains to a window according to the aspect (15), wherein first layered firm comprises a scratch resistant layer formed of one of the one or more higher refractive index materials and having a thickness of greater than or equal to 500 nm.

[00220] An aspect (17) of the present disclosure pertains to a window according to the aspect (16), wherein the thickness of the scratch resistant layer is greater than or equal to 1500 nm and less than or equal to 5000 nm.

[00221] An aspect (18) of the present disclosure pertains to a window according to the aspect (17), wherein the scratch resistant layer is separated from the terminal surface by a plurality of the alternating layers of the one or more lower index materials and the one or more higher index materials of the first layered film.

[00222] An aspect (19) of the present disclosure pertains to a window according to the aspect (18), wherein the scratch resistant layer is separated from the terminal surface by at least 1000 nm.

[00223] An aspect (20) of the present disclosure pertains to a window according to any of the aspects ( 1 )-(l 9), wherein the one or more higher refractive index materials of the second layered film comprise silicon.

[00224] An aspect (21) of the present disclosure pertains to a window according to the aspect (20), wherein the second layered film comprises two or more silicon layers.

[00225] An aspect (22) of the present disclosure pertains to a window according to the aspect (21), wherein a silicon layer of the second layered film most proximate to the substrate comprises the smallest thickness of the two or more silicon layers.

[00226] An aspect (23) of the present disclosure pertains to a window according to the aspect (21), wherein a combined thickness of the silicon layers contained in the second layered film is greater than or equal to 250 nm.

[00227] An aspect (24) of the present disclosure pertains to a window according to the aspect (22), wherein the combined thickness is greater than or equal to 500 nm. [00228] An aspect (25) of the present disclosure pertains to a window according to any of the aspects (21)-(24), wherein a layer of the one or more higher refractive index materials in the second layered film is not silicon.

[00229] An aspect (26) of the present disclosure pertains to a window according to any of the aspects ( 1 )-(25), wherein the maximum hardness, measured at the first layered film and by the Berkovich Indenter Hardness Test, is at least 10 GPa.

[00230] An aspect (27) of the present disclosure pertains to a window according to any of the aspects (l)-(26), wherein a hardness, measured at the first layered film and by the Berkovich Indenter Hardness Test, is at least 8 GPa over a depth range of 300 nm to 2000 nm.

[00231] An aspect (28) of the present disclosure pertains to a window according to any of the aspects (l)-(27), wherein a hardness, measured at the first layered film and by the Berkovich Indenter Hardness Test, is at least 9 GPa over a depth range of 750 nm to 2000 nm.

[00232] An aspect (29) of the present disclosure pertains to a window for a sensing system comprising: a substrate comprising a first surface and a second surface, the first surface and the second surface being primary surfaces of the substrate; a first layered film disposed on the first surface of the substrate, the first layered film comprising alternating layers of one or more higher refractive index materials and one or more lower refractive index materials, wherein refractive indices of the one or more higher refractive index materials of the first layered film are higher than refractive indices of the one or more lower refractive index materials of the first layered film; a second layered film disposed on the second surface of the substrate, the second layered film comprising alternating layers of one or more higher refractive index materials and one or more lower refractive index materials, wherein refractive indices of the one or more higher refractive index materials of the second layered film are higher than refractive indices of the one or more lower refractive index materials of the second layered film; and a maximum hardness, measured at the first layered film and by the Berkovich Indenter Hardness Test, of at least 8 GPa, wherein the quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films are configured so that the window has: an average reflectance, calculated over a 50 nm wavelength range of interest between 1400 nm and 1600 nm, of less than 0.5% for light incident on the first surface and the second surface at angles of less than or equal to 15°; a CIELAB L* value of less than or equal to 45 for angles of incidence of less than or equal to 60° on the first layered film; and CIELAB a* and b* values of greater than or equal to -6.0 and less than or equal to 6.0 when viewed from a side of the first layered film.

[00233] An aspect (30) of the present disclosure pertains to a window according to the aspect (29), wherein the CIELAB L* value is less than or equal to 30 for angles of incidence of less than or equal to 60° on the first layered film.

[00234] An aspect (31) of the present disclosure pertains to a window according to any of the aspects (29)-(30), wherein the quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films are configured so that the window has an average percentage transmittance, calculated over the 50 nm wavelength range of interest between 1400 nm and 1600 nm, of greater than 95% for light incident on the first surface and the second surface at angles of incidence of less than or equal to 15°.

[00235] An aspect (32) of the present disclosure pertains to a window according to any of the aspects (29)-(31), wherein the quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films are configured so that the window has an average percentage transmission, calculated from 400 nm to 700 nm, of less an 5% for light incident on the first surface and the second surface at angles of incidence of less than or equal to 15°.

[00236] An aspect (33) of the present disclosure pertains to a window according to any of the aspects (29)-(32), wherein the quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films are configured so that the window has an average P polarization transmittance and an average S polarization transmittance, calculated over the 50 nm wavelength range of interest between 1400 nm and 1600 nm, of greater than 85% for light incident on the first surface and the second surface at angles of incidence of less than or equal to 60°.

[00237] An aspect (34) of the present disclosure pertains to a window according to the aspect (33), wherein the average P polarization transmittance and the average S polarization transmittance, calculated over the 50 nm wavelength range of interest between 1400 nm and 1600 nm, are greater than 92% for light incident on the first surface and the second surface at angles of incidence of less than or equal to 60°.

[00238] An aspect (35) of the present disclosure pertains to a window according to any of the aspects (29)-(34), wherein the quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films are configured so that the window has an average reflectance, calculated throughout the visible spectrum, for light normally incident on the first layered film, of less than or equal to 10%.

[00239] An aspect (36) of the present disclosure pertains to a window according to any of the aspects (29)-(35), wherein the quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films are configured so that the window has an average percentage transmittance, calculated over the 50 nm wavelength range of interest between 1400 nm and 1600 nm, of greater than 95% for light normally incident on the first surface and the second surface.

[00240] An aspect (37) of the present disclosure pertains to a window according to any of the aspects (29)-(36), wherein the maximum hardness, measured at the layered film and by the Berkovich Indenter Hardness Test, is at least 10 GPa.

[00241] An aspect (38) of the present disclosure pertains to a window according to any of the aspects (29)-(37), wherein a hardness, measured at the first layered film and by the Berkovich Indenter Hardness Test, is at least 8 GPa over a depth range of 300 nm to 2000 nm.

[00242] An aspect (39) of the present disclosure pertains to a window according to any of the aspects (29)-(38), wherein: one of the alternating layers of the first layered film that is farthest from the substrate forms a terminal surface material of the window, the terminal surface material of the window comprising the lower refractive index material, the first layered firm comprises a scratch resistant layer formed of one of the one or more higher refractive index materials and having a thickness that is greater than or equal to 1500 nm and less than or equal to 5000 nm.

[00243] An aspect (40) of the present disclosure pertains to a window according to the aspect (39), wherein: the scratch resistant layer is separated from the terminal surface by a plurality of the alternating layers of the one or more lower index materials and the one or more higher index materials of the first layered film, and the scratch resistant layer is separated from the terminal surface by at least 1000 nm.

[00244] An aspect (41) of the present disclosure pertains to a window according to any of the aspects (29)-(40), wherein the one or more higher refractive index materials of the second layered film comprise silicon.

[00245] An aspect (42) of the present disclosure pertains to a window according to the aspect (41), wherein the second layered film comprises two or more silicon layers. [00246] An aspect (43) of the present disclosure pertains to a window according to the aspect (43), wherein a silicon layer of the second layered film most proximate to the substrate comprises the smallest thickness of the two or more silicon layers.

[00247] An aspect (44) of the present disclosure pertains to a window according to the aspect (43), wherein a combined thickness of the silicon layers contained in the second layered film is greater than or equal to 250 nm.

[00248] An aspect (45) of the present disclosure pertains to a window according to the aspect (44), wherein the combined thickness is greater than or equal to 500 nm.

[00249] An aspect (46) of the present disclosure pertains to a window according to any of the aspects (42)-(45), wherein a layer of the one or more higher refractive index materials in the second layered film is not silicon.

[00250] An aspect (47) of the present disclosure pertains to a window for a sensing system comprising: a substrate comprising a first surface and a second surface, the first surface and the second surface being primary surfaces of the substrate; a first layered film disposed on the first surface of the substrate, the first layered film comprising alternating layers of one or more higher refractive index materials and one or more lower refractive index materials, wherein refractive indices of the one or more higher refractive index materials of the first layered film are higher than refractive indices of the one or more lower refractive index materials of the first layered film; a second layered film disposed on the second surface of the substrate, the second layered film comprising alternating layers of one or more higher refractive index materials and one or more lower refractive index materials, wherein refractive indices of the one or more higher refractive index materials of the second layered film are higher than refractive indices of the one or more lower refractive index materials of the second layered film, wherein the one or more higher refractive index materials of the second layered film comprises silicon; and a maximum hardness, measured at the first layered film and by the Berkovich Indenter Hardness Test, of at least 8 GPa, wherein the quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films are configured so that the window has: an average reflectance, calculated over a 50 nm wavelength range of interest between 1400 nm and 1600 nm, of less than 1% for light incident on the first surface and the second surface at angles of less than or equal to 15°; and an average percentage transmittance, calculated over the 50 nm wavelength range of interest between 1400 nm and 1600 nm, of greater than 90% for light incident on the first surface and the second surface at angles of incidence of less than or equal to 15°. [00251] An aspect (48) of the present disclosure pertains to a window according to the aspect (47), wherein the quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films are configured so that the window has an average percentage transmission, calculated from 400 nm to 700 nm, of less an 5% for light incident on the first surface and the second surface at angles of incidence of less than or equal to 15°. [00252] An aspect (49) of the present disclosure pertains to a window according to any of the aspects (47)-(48), wherein the quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films are configured so that the window has an average P polarization transmittance and an average S polarization transmittance, calculated over the 50 nm wavelength range of interest between 1400 nm and 1600 nm, of greater than 85% for light incident on the first surface and the second surface at angles of incidence of less than or equal to 60°.

[00253] An aspect (50) of the present disclosure pertains to a window according to the aspect (49), wherein the average P polarization transmittance and the average S polarization transmittance, calculated over the 50 nm wavelength range of interest between 1400 nm and 1600 nm, are greater than 92% for light incident on the first surface and the second surface at angles of incidence of less than or equal to 60°.

[00254] An aspect (51) of the present disclosure pertains to a window according to any of the aspects (47)-(50), wherein the quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films are configured so that the window has a CIELAB L* value of less than or equal to 45 for angles of incidence of less than or equal to 60° on the first layered film.

[00255] An aspect (52) of the present disclosure pertains to a window according to the aspect (51), wherein the CIELAB L* value is less than or equal to 30 for angles of incidence of less than or equal to 60° on the first layered film.

[00256] An aspect (53) of the present disclosure pertains to a window according to any of the aspects (47)-(52), wherein the quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films are configured so that the window has CIELAB a* and b* values of greater than or equal to -6 and less than or equal to 6 when viewed from a side of the first layered film.

[00257] An aspect (54) of the present disclosure pertains to a window according to any of the aspects (47)-(53), wherein the quantity, the thicknesses, number, and materials of the alternating layers of the first and second layered films are configured so that the window has an average reflectance, calculated throughout the visible spectrum, for light normally incident on the first layered film, of less than or equal to 10%.

[00258] An aspect (55) of the present disclosure pertains to a window according to any of the aspects (47)-(54), wherein: one of the alternating layers of the first layered film that is farthest from the substrate forms a terminal surface material of the window, the terminal surface material of the window comprising the lower refractive index material, the first layered firm comprises a scratch resistant layer formed of one of the one or more higher refractive index materials and having a thickness that is greater than or equal to 1500 nm and less than or equal to 5000 nm.

[00259] An aspect (56) of the present disclosure pertains to a window according to the aspect (55), wherein: the scratch resistant layer is separated from the terminal surface by a plurality of the alternating layers of the one or more lower index materials and the one or more higher index materials of the first layered film, and the scratch resistant layer is separated from the terminal surface by at least 1000 nm.

[00260] An aspect (57) of the present disclosure pertains to a window according to any of the aspects (47)-(56), wherein the second layered film comprises two or more silicon layers. [00261] An aspect (58) of the present disclosure pertains to a window according to the aspect (57), wherein a silicon layer of the second layered film most proximate to the substrate comprises the smallest thickness of the two or more silicon layers.

[00262] An aspect (59) of the present disclosure pertains to a window according to the aspect (57), wherein a combined thickness of the silicon layers contained in the second layered film is greater than or equal to 250 nm.

[00263] An aspect (60) of the present disclosure pertains to a window according to the aspect (59), wherein the combined thickness is greater than or equal to 500 nm.

[00264] An aspect (61) of the present disclosure pertains to a window according to any of the aspects (57)-(60), wherein a layer of the one or more higher refractive index materials in the second layered film is not silicon.

[00265] An aspect (62) of the present disclosure pertains to a window according to the aspect (61), wherein the layer of the one or more higher refractive index materials in the second layered film that is not silicon is the layer of the one or more higher refractive index materials that is most proximate to the substrate.

[00266] It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit or scope of the claims.