TECHNICAL FIELD

The invention relates to optical scattering control units providing spatial control, scattering control of the incident light in the nanophotonics field.

PRIOR ART

The behavior of light of a certain wavelength after interaction with matter is generally described as “scattering”. The material properties, geometric shape, dimensions and diameter of the interacting matter also determine its interaction with light.

The scattering effects generally studied in the current technique are divided into two, as “Rayleigh” and “Mie” scattering. Matters with dimensions much smaller than the wavelength of the incident light scatter light isotropically and act like a dipole source. If the geometric size of the matter is close to or larger than the wavelength of the incident light, the scattering behavior exhibits an anisotropic (not isotropic) light intensity distribution depending on the geometric size. The scattering behavior of spherical matters has been analytically demonstrated.

When the interactions of Mie scattering matters with light are examined mathematically, it is observed that more than one orthogonal electrical and magnetic modes (dipole/quadrupole/octapole, etc.) can emerge, and as a result of far-field interferences of the fields formed by these modes, the scattering response of the matter depending on the angle is obtained.

The scattering pattern of the matter can be changed by adjusting the wavelength of the incident light or the geometric parameters of the respective matter. Generally, it is not possible to change the geometric properties after production, since a study is carried out at a specific wavelength.

Metasurface structures are known in the art. These structures, nanophotonic resonators with geometric dimensions smaller than the wavelength of the modulated light, scatter the incident light according to Mie analysis. Resonators, which can be grouped under two general subheadings as Plasmonic (materials with negative dielectric constant, usually metals) and Dielectric (materials with positive dielectric constant, semiconductors) materials, are designed according to the wavelength to be modulated. In plasmonic systems, electrical losses (surface currents) at high optical frequencies are high. Dielectric systems, which is another subheading, suffer much less loss due to the displacement currents formed within them. However, the compatibility of integrated circuit production facilities with process and material capabilities considerably shortens the commercialization period of the system.

Dielectric systems can be examined under two subheadings as passive and active. In passive systems, nano-resonators produced according to the material and geometric shape selected based on the wavelength to be used can only exhibit the scattering pattern for which they are designed, and a different intensity/spatial angle distribution cannot be obtained as desired later on. Active systems are systems that have emerged to provide a solution to this problem.

In the article “Metasurfaces for Spatial Light Manipulation” by Jian Wang and Jing Du, use of passive metasurfaces in manipulating the spatial distribution of light is disclosed.

In the document US2017219739, a system comprising more than one metasurface with different physical properties and thus controlling the spatial scattering of light is mentioned.

In the application WO2016168173, a system where scattering is controlled via metasurfaces with different geometrical structures is disclosed.

In active metasurface systems, in general, resonance frequency of the material selected as the resonator, and thus optical properties thereof, can be changed by means of methods such as electrical, magnetic, optical, mechanical, thermal, etc., thereby intensity, phase angle or polarization of the incident light can be controlled. However, the spatial distribution and intensity of the light scattered from the resonator cannot be controlled.

Scattering of a plane wave light beam from a plasmonic or dielectric sphere has been analytically and fully demonstrated by Gustav Mie by solving Maxwell’s equations in spherical coordinates. By solving the related mathematical equations, it is concluded that there are different optical modes (electrical, magnetic, toroidal etc.) scattered from the sphere. At optical wavelengths, plasmonic spherical bodies behave like electric dipoles due to electric currents occurring only on their surfaces, and other optical modes do not emerge. On the contrary, dielectric spherical bodies can provide a much richer modulation capacity due to different displacement current modes that may occur within them, thereby magnetic and toroidal modes can also affect the optical modulation of the system. A practical application of said effects is a system called as Huygens’ metasurface. In order for the Huygens’ effect to be observed, the electric and magnetic dipole resonances must overlap at the wavelength studied. If the relevant condition is met, the incident light on the system is only scattered in forward direction and efficiency thereof is close to 100%, and also phase adjustment can be made between 0 and 360 degrees.

As a result, all of the above-mentioned problems have made it necessary to make an innovation in the related technical field.

BRIEF DESCRIPTION OF THE INVENTION

The present invention relates to an optical scattering control unit in order to eliminate the above-mentioned disadvantages and bring new advantages to the related technical field.

An object of the invention is to realize an optical scattering control providing control of the spatial distribution of the incident light.

Another object of the invention is to allow to make the changes in the spatial distribution of light in an accelerated way.

In order to achieve all objects mentioned above and will emerge from the following detailed description, the present invention is an optical scattering control unit comprising an optical resonator. Accordingly, said optical resonator has a nano-structure and comprises at least one Huygens’ metasurface unit with a controlled response to both electric and magnetic fields; it comprises an external electric field source configured to apply a controlled electric field to said Huygens’ metasurface to control the scattering of the incident light beam of a first spectrum. Thereby, the spatial distribution of light is controlled, and since it is directly proportional to the rate of change of the electric field, the transition rate of the spatial distribution between two distributions is increased.

A possible embodiment of the invention is characterized in that said external electric field source comprises a first layer and a second layer provided to interpose the Huygens’ metasurface unit; said first layer and second layer are structured to pass light beams of the first spectrum. Thereby, in the absence of an electric field, the light passing through the layers can pass directly through the optical resonator without deflection, and its spatial distribution can change when an electric field is applied.

A possible embodiment of the invention is characterized in that the first layer, the second layer and the optical resonator are formed on a substrate.

A possible embodiment of the invention is characterized in that said substrate is at least one of glass, silicon, quartz and silicon oxide.

Another possible embodiment of the invention is characterized in that it comprises multiple Huygens’ metasurface units side by side such that one side thereof is associated with the first layer and the other, opposite side is associated with the second layer; the first layer and/or the second layer comprises an electronic control circuit to control the electric field provided in the neighborhood of each Huygens’ layer. Thereby, the spatial scattering of different light beams can be controlled simultaneously independent of each other.

Another possible embodiment of the invention is characterized in that said control circuits comprise at least one transistor and at least one capacitor.

Another possible embodiment of the invention is characterized in that said first layer and/or second layer and electronic control circuits contain ITO and ZnO.

Another possible embodiment of the invention is characterized in that, for independent control of Huygens’ metasurface units, the first layer and/or the second layer are active or passive thin-film transistors (TFT).

Another possible embodiment of the invention is characterized in that the external electric field source is configured to selectively operate in a first mode in which it is in a passive state to pass the incident light beam directly, and in at least one second mode in which the Huygens’ metasurface unit emits an electric field of the same intensity as the electric field it emits when the light beam passes through it and of opposite direction to this field.

The invention is also a fiber optic multiplexer comprising an optical scattering control unit as described above. Thus, a fiber optic multiplexer that responds faster than the current technique is obtained. BRIEF DESCRIPTION OF THE FIGURES

A representative view of the optical scattering control unit is given in Figure 1 .

A representative view of operation of the optical scattering control unit in the first mode is given in Figure 1 a.

A representative view of its operation in the second mode is given in Figure 1 b.

A representative view of an embodiment in which the optical scattering control unit comprises multiple Huygens’ metasurface units is given in Figure 2.

DETAILED DESCRIPTION OF THE INVENTION

In this detailed description, subject matter of the invention is only explained by way of examples for understanding the subject matter better that will not have any limiting effect.

Referring to Figure 1 , the present invention is an optical scattering control unit (100). It comprises an optical resonator (110). Essentially, it allows by the optical resonator (110) comprising a Huygens’ metasurface unit and via an external electric field source (120) contained in the optical scattering control unit (100), to pass the incident light on said Huygens’ metasurface directly through it according to the electric field emitted by the electric field source or to change the spatial distribution thereof. The optical resonator (110) has nano-structure.

In more detail, the optical resonator (110) comprises a Huygens’ metasurface unit. The Huygens’ metasurface unit can be provided in the form of layers.

In an embodiment of the invention as in figure 1 , also the external electric field source (120) can comprise a first layer (121) and a second layer (122) interposing the Huygens’ metasurface unit. Said first layer (121), second layer (122) and optical resonator (110) are formed on a substrate (123). Said substrate can be at least one of glass, silicon, quartz and silicon oxide. The first layer (121) and the second layer (122) have a light permeable structure in the spectrum where light beams whose spatial scattering is controlled are present. In a possible embodiment of the invention, the external electric field source (120) may comprise at least one control unit (not shown in the figures) that controls the characteristic of the electric field applied by the first layer (121) and the second layer (122).

The incident light on the Huygens’ metasurface unit passes directly through it without loss in the absence of an electric field. Referring to Figure 1a, in a possible embodiment of the invention the external electric field source (120) operates in a first mode (I) such that the incident light on the Huygens’ metasurface unit passes through it and continue in the same direction. Referring to Figure 1 b, in a possible embodiment of the invention the external electric field source (120) allows the incident light beam on the Huygens’ metasurface unit to exhibit a different spatial scattering compared to that in the first mode (I). For example, when the light beam passes through the Huygens’ metasurface unit, the external electric field source (120) emits an electric field of the same intensity as the electric field emitted by the Huygens’ metasurface unit and of opposite direction, and causes the Huygens’ metasurface unit to emit the incident light beam by spherical scattering. In a possible embodiment of the invention when the geometry of the Huygens’ metasurface unit is selected accordingly, while a linear propagation can be seen when the electric field is applied; a spherical propagation can be seen when the electric field is not applied.

In a possible embodiment as in Figure 2, the optical resonator (110) comprises more than one Huygens’ metasurface unit. The Huygens’ metasurface units are provided such that one side thereof contacts with the first layer (121), and one side opposite to this side contacts with the second layer (122). In this embodiment, the electric field control unit comprises multiple electronic control circuits (125) provided in the first layer (121) to allow to control each Huygens’ metasurface unit independent of each other. Said electronic control circuits are provided in the neighborhood of each Huygens’ metasurface unit (111 ). Electronic control circuits comprises the capacitor and transistor. Here, the first layer (121 ) or the second layer (122) may comprise an active or passive thin-film transistor (TFT).

First layer (121), second layer (122) and electronic control circuits can be produced with Indium-Tin-Oxide (ITO) or Zinc-Oxide (ZnO) and with appropriate doping.

The invention allows to change the relative effect thereof according to the magnetic dipole mode and thereby obtain a different scattering spatial pattern by controlling the amplitude of the electrical dipole mode of the resonator designed as Huygens’ metasurface (equal and reverse phase electrical and magnetic dipole modes) with the applied additional electric field. By using the phenomenon of superposing (superposition) of electric fields at a point in space, in accordance with the “Maxwell Electromagnetic Field Equations”, the intensity of the electric field within the optical resonator (110) is controlled thanks to superposition of vectors belonging to the electric field that will be created by the radiation within the optical resonator (110) and belonging to the stable or time-varying electric field that will be applied externally. The magnetic dipole mode will not be affected because the magnetic dipole mode occurs based on the principle that the electric field of the incident light creates parallel and opposite displacement currents in the optical resonator (110), consequently a circular current path forms and circular currents create a magnetic field and since the electric field applied externally is perpendicular to the displacement currents. Thereby, electric and magnetic dipole fields can be controlled relatively.

The invention can be used for routing data in fiber optic systems to different and desired ports for telecommunication and information sectors, in spatial control of light in optical microchips; in the analysis of cells or matters circulating in the body, determining the cell/matter type according to the analysis, and creating different Moire patterns for high resolution imaging for health and bioelectronics sectors.

The scope of protection of the invention is defined in the attached claims and cannot be limited in any way to what is described in this detailed description for exemplary purposes. It is obvious that a person skilled in the art can provide similar embodiments in the light of what has been described above without departing from the main theme of the invention.

REFERENCE NUMBERS GIVEN IN THE FIGURES

100 Optical scattering control unit

110 Optical resonator 111 Huygens’ metasurface unit

120 External electric field source

121 First layer

122 Second layer

123 Substrate 125 Electronic control unit

I First mode

II Second mode