TECHNOLOGICAL FIELD AND BACKGROUND

During the last decades of the previous century, significant advances have been made in the manufacture of electrical circuits and components. The advent of printed circuit board technology, combined with pick and place surface mount technology (SMT), has allowed an unprecedented reduction in size and complexity of electrical subsystems, with a corresponding reduction in cost, and increase in speed of manufacture, and ease of integration. PCBs and SMT technology is now so ubiquitous that hobbyists are routinely manufacturing complex circuit boards (both at home, and through mail order companies) and constructing home-made reflow ovens to allow then to design and create electronic system which could once only be achieved by companies with dedicated manufacturing facilities.

Today, optical technology is at the same phase as electronic was several decades ago. Optical systems are complex, hand wired, and costly, placing them beyond the grasp of most hobbyists, and requiring much time and effort to construct and use. A major part of a researcher's time and effort, for example, is currently dedicated to the simple, yet time consuming, tasks of designing, constructing, and maintaining simple optical systems, which are used as parts of larger experimental setups.

Printed optics technology has been developed for creating custom optical elements for interactive devices using 3D printing. This technology enables sensing, display, and illumination elements to be directly embedded in the body of an interactive ted optics

This technique utilizes today's 3D printing technology for providing 3D printing custom optical elements for interactive devices. Such Printed Optics techniques enables sensing, display, and illumination elements to be directly embedded in the casing or mechanical structure of an interactive device. Using these elements, unique display surfaces, novel illumination techniques, custom optical sensors, and embedded optoelectronic components can be digitally fabricated for rapid, high fidelity, highly customized interactive devices. Printed Optics is part of a long term vision for interactive devices that are 3D printed in their entirety.

US 8,488,920 describes an optical printed circuit board, comprising: plural polymer waveguide sections from independent waveguides, each of the sections being doped with an amplifying dopant; an optical pump source to pump the plural polymer waveguide sections, wherein the plural waveguide sections are arranged close or adjacent to one another such that a the optical pump source is able to pump plural of the optical waveguide sections.

GENERAL DESCRIPTION

There is a need in the art for a novel approach for constructing optical systems by introducing concepts similar to those as electronics systems, of pre-routed boards, containing optical circuitry, and the introduction of the "pick and place" analog to optical components. The present invention provides a novel Optical Circuit Board (OCB) structure configured for mounting optical components thereon. The OCB of the invention may be integrated, in a straightforward manner, with standard electronic circuit techniques, to allow the construction of simple, integrated, electro-optical systems.

As indicated above, the general concept of printed optics has been proposed by Disney Research. In this method, however, all the elements of an optical device are 3D printed in their entirety, which results in inherently lower quality of optical components, far from the standard required for true research grade devices.

The present invention provides a novel optical platform configured for mounting thereon optical components, which are prepared independently (i.e. separately from the optical platform). This technique allows for avoiding the limitations of 3D printing technology for manufacture of at least some of optical components, and allows for using off-the-shelf, high-quality, optical components.

The invention provides a novel approach for an optical device of the kind including: optical components (e.g. lenses, beam splitters, etc.) which are referred to herein as "active" optical components affecting properties of incident light and/or its propagation (active optical components may or may not be tunable); and light guiding elements which are referred to herein as "passive" elements in the meaning that they include waveguides / fibers optically connecting the active optical components, and support structures for holding the active optical components.

More specifically, according to the invention, the passive elements are integral with an optical platform (also termed here optical board or optical circuit board (OCB) or optical printed circuit board (OPCB) and such optical platform is manufactured by 3D printing technique to create a 3D optical pattern of the passive elements. The features of the optical pattern correspond to the arrangement / pattern of external active optical components (that are manufactured independently, and not necessarily being 3D printed ones) for being mounted on the optical platform. This enables use of high- quality, optical components which practically cannot be obtained by the conventional 3D printing techniques in a cost effective manner. The active optical components (e.g. including off-the-shelf components) are mounted on the dedicated optical platform, which has been previously separately fabricated, and carries passive elements arranged in a predetermined 3D optical pattern (according to the optical device circuit).

Thus, the invention provides a novel optical platform, carrying an optical pattern of passive elements and configured for mounting external active optical components on said platform in a predetermined locations while providing optical coupling between the active optical components. It should be noted that although the optical platform of the invention is at times referred to herein below as Optical Circuit Board (OCB), it is essentially different from the known OCBs. The optical platform of the invention is manufactured by a novel method resulting in a different structure. The optical platform structure of the invention includes a substrate, and a plurality of waveguides (generally, light guides/paths) which are integral with the substrate while being suspended from the substrate. In the optical platform of the invention, the substrate and the passive elements integral therewith may be made of the same material composition. This is contrary to the known structures of the kind specified, in which waveguides are either embedded in a substrate or form a surface pattern on the surface of the substrate, and are thus typically formed by material composition(s) different from that of the substrate.

The optical platform structure of the invention is manufactured by a continuous

3D printing process resulting in an integral structure, i.e. the integral structure comprised of the substrate and an optical circuit pattern formed by suspended waveguides and chassis mounts. According to the preferred embodiments of the invention, the method of the invention for manufacturing such optical platform structure utilizes layer-by-layer creation of successive sub-patterns of the entire optical circuit pattern, by polymerization of a basic (precursor) monomer composition of the substrate.

According to the invention, electronic and fluidic components/devices are fully integrated, vastly extending the capabilities of the envisioned devices, to allow for fully usable "lab-on-board" and "experiment-on-board" applications.

Three dimensional printing has evolved into a paradigm shifting technology in recent years. The ability to replicate and design, at home, structures down to the micron scale at less than 10k$ is at hand. Several technologies have emerged, including laser sintering, Fused Deposition Modeling (FDM) via extrusion, and photopolymerization.

The present invention provides a novel optical circuit board (OCB) which comprises a 3D printed optical pattern defining one or more chassis mounts configured for mounting one or more optical components thereon and defining one or more optical waveguides for optically coupling said optical components, when mounted on said one or more chassis mounts.

As explained above, the term "active component" or "optical component" or "active optical component" used herein refers to an element, component or device, being either passive or active in the meaning that components is tunable or non-tunable, and which is capable of optically processing input optical signals. These active components should be distinguished from the elements of the 3D printed optical pattern (waveguides, optical input and output ports, etc.), serving mainly as connecting and light guiding utilities, as well as other media circuits. The printed 3D pattern may also define one or more fluidic cells being in optical communication with one or more of the waveguides, thus extending the capabilities of the system for example to biology, spectroscopy and nonlinear fluid control, switching and amplification in liquid dyes and nematic polarization rotation.

Thus, instead of 3D printing of the optical components, the present invention provides an optical circuit board composed of a substrate carrying a 3D printed pattern of the waveguide(s) and chassis mount(s) configured for mounting thereon external optical components, wherein said 3D pattern is integral with the substrate (made of or including the same material as the substrate) and suspended from the substrate's surface. The inventors have shown that commercially available transparent 3D printable materials have the required transparency and index of refraction to provide desired material quality and smoothness.

The 3D pattern may be printed within a polymer material composition by light induced polymerization or stereolithography, thereby providing features size of the pattern as small as a few microns.

According to one broad aspect of the invention, there is provided an optical circuit board comprising a substrate and a 3D optical pattern integral with said substrate and being suspended from a surface of the substrate, the 3D optical pattern being configured to define a predetermined arrangement of one or more optical waveguide circuits and chassis mounts, the chassis mounts being configured for mounting thereon one or more predetermined external optical components, and said one or more optical waveguide circuits being configured for providing light propagation to and from said one or more optical components, when mounted on said one or more of the chassis mounts.

In some embodiments, the substrate and the 3D optical pattern are formed by light induced polymerization of successive layers in a basic monomer material composition.

The invention, in its further aspect provides an optical circuit board comprising a substrate carrying a 3D optical pattern integral with a surface of the substrate and defining a predetermined arrangement of optical waveguide circuit(s) suspended from the surface of the substrate, and chassis mounts configured for mounting thereon one or more predetermined external optical components, features of said 3D optical pattern being formed by polymerized regions of a basic monomer material composition of the substrate.

In some embodiments, the substrate is configured as a printed circuit board comprising an electronic circuit pattern printed on the surface of the substrate.

According to another broad aspect of the invention, there is provided an optical device comprising the above described optical circuit board and active optical components mounted on the chassis mounts.

According to yet another broad aspect of the invention, it provides a method for manufacturing an optical circuit board comprising a substrate and a 3D optical pattern integral with said substrate, defining a predetermined arrangement of optical waveguide circuit(s) suspended from the surface of the substrate, and chassis mounts configured for mounting thereon one or more predetermined external optical components. The method comprises: providing a basic monomer material composition; providing reference data indicative of features of successive sub-patterns in said 3D optical pattern; utilizing the reference data for operating a printing system for creating the successive sub-patterns by light induced polymerization of the basic monomer material composition.

According to yet another aspect of the invention, there is provided an electro- optical circuit board which comprises an electrical printed circuit board (PCB) integrated with the OPCB of the invention. The OPCB (i.e. a substrate with the integral and suspended pattern of waveguide(s) and chassis mounts) may be printed on a surface of the PCB, enabling coupling one or more electro-optical active components, when mounted on the electro-optical circuit board, between electrical circuits of the PCB and the printed waveguide circuits of the OPCB.

The invention in its yet further aspect provides an electro-optical device comprising the above described electro-optical circuit board, i.e. comprising a PCB and an OCB printed on a surface of the PCB.

In some embodiments of the invention, multimode optical waveguides are printed in the optical board, which may be vector printed onto a cladding polymer, at a few tens of micron resolution, and then coated over by printing with the cladding polymer to achieve a high quality optical fiber network. As part of the process, placement chassis are printed for optical components to be mounted thereof, such as collimation lenses, beamsplitters, as well as nonlinear crystals and modulators (electro optical and acousto optical). The latter require electrical contacts and routing, which can either be produced separately using standard printed circuit board techniques, or may be integral in the OCB of the invention, e.g. being produced from conductive polymers.

The novel OCB approach of the present invention provides a bridge between gross, hand controlled expensive and sensitive lab optics, to truly micro-optical chip- scale designs being developed for next generation computing and memory.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to better understand the subject matter that is disclosed herein and to exemplify how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:

Fig. 1 illustrates the principles of the invention for constructing optical devices; Figs. 2 A and 2B exemplify an experimental structure of optical circuit board of the invention showing an array of suspended fibers (optical pattern) carried on and integral with a substrate obtained by 3D printing technique (Fig. 2A), and light guiding and outcoupling of light in the structure (Fig. 2B);

Fig. 3 schematically illustrates an example of the OCB configuration according to the invention; and

Fig. 4 illustrates a graph corresponding to the loss fraction as a function of the bend radius for 3D printing of waveguides on the OCB.

DETAILED DESCRIPTION OF EMBODIMENTS

Reference is made to Fig. 1 illustrating the main principles of the invention.

Fig. 1 shows schematically an optical circuit board (OCB) 10 of the present invention. The OCB 10 is an integral structure formed by a substrate 12 and an optical pattern 14. The optical pattern 14 is configured to define a circuit of connecting and light guiding elements, such as waveguides, generally at 14A, and chassis mounts 14B. As shown in the figure, the optical pattern 14 is suspended from surface 12A of the substrate 12.

As also shown in the figure, the structure 10 is a 3D printed structure, which is formed by continuously, layer-by-layer, defining (printing) layers Li - L„, each being a sub-pattern of the entire optical pattern 14. According to some embodiments of the invention, such creation of successive sub-patterns of the entire optical circuit pattern 14, is implemented by layer-by-layer polymerization of a basic monomer composition of the substrate 14. For example, known UV curing technique can be used for this purpose, according to which UV curing radiation is successively focused on n successive planes within the basic monomer composition.

To this end, reference data about required arrangement of waveguides and other elements of the pattern (e.g. connecting, supporting, and guiding elements) is provided. Such data is typically prepared based on the design of the final optical device to be provided, which in turn includes the arrangement of active optical components and optical connection between them.

As schematically shown in Fig. 1, a control system (computer system) 16, which has access to (e.g. includes in its internal memory 16A) the reference data about the required optical pattern 14, and includes a controller 16B preprogrammed for using the optical pattern data for controlling operation of a printing system 18 to create successive layers (sub-patterns) of pattern 14. For example, considering the layer-by-layer polymerization of a basic monomer composition is used for the 3D printing, the parameters of the printing system 18 to be controlled may include an operating wavelength for curing (typically 405nm or less), exposure duration per layer, optical resolution (e.g. of at least 30 microns for the waveguide printing), etc.

The control system 16 may be integral with the printing system 18. It should be noted, although not specifically shown, that the control system 16 may include a processor module, which may for example be configured for processing input data indicative of the arrangement of active components and required optical coupling between them (generally, required operation of the final optical device), and generating the reference data about the suitable optical pattern 14. The inventors have prepared an experimental optical circuit board and demonstrated the waveguides operation. In this connection, reference is made to Figs. 2A and 2B showing the experimental results. Figs. 2A shows an array of suspended fibers (constituting optical pattern 14) integral with and suspended from the surface 12A of the substrate. The entire OCB was obtained by 3D printing technique. In this example commercially available 3D printer Asiga PicoPlus33 was used, with the PlasClear material for OCB formation. This 3D printer operates with light of 405 nm wavelength to cure the PlasClear. The 3D printed optical pattern was formed including waveguides of 100 microns width suspended 300 microns above the surface of the substrate. Exposure time was 2.3 seconds (for each layer). The printed structure was subsequently rinsed in Isopropanol and water to gently remove uncured material, and subsequently further hardened by a 20 minute exposure in the Asiga 405 nm flash box. Fig. 2B demonstrates light guiding and outcoupling of light from spot S of the waveguide array.

Turning back to Fig. 1, in some embodiments of the invention, the features of the OCB, i.e. surface 12A and 3D optical pattern 14, are formed by a predetermined arrangement of at least partially polymerized regions of the basic monomer material composition of the substrate.

Reference is made to Fig. 3 showing a specific but not limiting example of the configuration of an optical device 20 utilizing an optical circuit board (OCB) 10 of the present invention. The OCB 10 has a substrate 12 and a 3D optical pattern 14 integral with and suspended from the substrate's surface. The pattern 14 defines one or more optical waveguide circuits 14A and chassis mounts 14B configured for coupling to one or more optical components mountable on the optical circuit board 10. In the present not limiting example, the optical components include beam splitters 16 and lens 18. Also, in the present example, the 3D pattern 14 includes a fluidic cell 14C with its associated electrode assembly. The optical components are separately and independently prepared, e.g. fabricated by 3D printing, or being off-the-shelf high-quality components.

As indicated above, the OCB 10 is a 3D printed structure, which may for example be manufactured by successive printing, by light induced polymerization, sub- patterns of the pattern 14. Standard 3D printing techniques for plastics include Fused Deposition Modeling (FDM), sometime referred to as extrusion techniques, and light induced polymerization. In FDM techniques a preformed polymer is extruded via one or more small nozzles, typical feature sizes possible using this technique are larger than 100 μm. In contrast, in light induced polymerization, feature sizes can be as small as a few microns, with resolutions limited by the diffraction limit of the optics used, or by the nozzle diameters in inkjet-type techniques. The technique of the invention might require feature sizes, which are incompatible with FDM techniques, but which can be easily achieved using light-induced polymerization. Another benefit of such technique is the ability to dynamically alter the composition of the polymerized material, which may be used to change its optical properties (for example, its index of refraction). The present invention also provides for printing of larger scale structures for optical component chassis, which can be performed using any known 3D printing technologies.

The materials suitable to be used in the OCBs of the present invention include several types of polymers, of the standard types used in polyjet and stereolithography 3D printing. These materials have indices of refraction roughly around 1.5, and by changing the concentration of various material components the index of refraction may be varied by a few tens of percent. An example of such a material is VeroClear (produced by Stratasys Ltd.) which has similar properties to Poly(methyl methacrylate) (PMMA), commonly known as plexiglas, with a refractive index of 1.47 (650nm light source).

Current transparent polymer based materials exhibit attenuation lengths of order of several meters in the visible light range. With the proposed device dimensions, which are of the order of up to several tens of centimeters, this loss is negligible with the technique of the present invention.

With that in mind, the inventors have calculated the possible bend radii for printed light-guides. The light loss as a function of the bend radius can be calculated as:

where Df is the fiber (waveguide) diameter, n ₁ (n ₂ ) is the refractive index of the core (cladding), and R is the bend radius. Fig. 4 illustrates a graph corresponding to the loss fraction as a function of the bend radius, using typical values Df = 25 _m, η _Ύ = 1.47, n ₂ = 1.37. From the figure it is clear that bend radii of larger than approximately 2mm are possible without significant loss of light.

le future, 3D printing technology might not The present invention provides for using standard micro-optical components, which will be integrated into the devices by insertion into custom printed chassis. Such technology is widely used in the electronics industry via pick-and-place standards, and can be adapted to this application. Relevant micro-optical components include, for example, lenses, mirrors, waveplates, polarization elements, beam splitting elements, and the like. Such components are readily available via standard vendors, and due to their small size are comparatively inexpensive.

As indicated above, the present invention provides for using combined electronic and optical technologies on the same board. Active optical components, for example phase modulators, are electrically controlled and driven. The invention allows the explicit use of combined optical and electrical pick and pick and place technologies along with 3D printing of the optical interface. One implementation for example, is the 3D printing of the optical elements and chassis on a pre-existing printed circuit board (which already contains pads for the electrical components), by direct printing of the OCB of the invention (i.e. the optical pattern) for further mounting / assembling the optical components on the chassis mounts. These expand the capabilities of the proposed device to include active elements, enabling, for example, wavelength shifting, amplitude and phase modulation.

Most of the spectroscopic and dynamic measurements done in the so-called field of micro-fluidics actually require millimeter scale fluidic cells. The present invention provides for naturally integrating the ability to print such cells into the optical circuit. The fluid channels to such cells can also be printed as part of the 3D structure (optical pattern). Application for such integrated fluidic device are, for example, real time contaminant monitoring, spectroscopic analyses of suspect samples, and active light control using electro-responsive fluids, such as nematic and ferro-fluids.

Referring back to Fig. 3, it shows an artist's rendition of a possible implementation for a printed optics board containing light guides, a lens, beam splitting elements, a fluidic cell, and a means of modulation of such cell (namely, an electrode). Such a design can be used, for example, as an interferometer. The electrode can be produced using standard PCB techniques, while the light guides, fluidic cell, and chassis for the optical elements can be 3D printed pattern on the aforementioned PCB being suspended from its surface. Placement of the optical components (lens, etc.) can be performed in a pick-and-place manner, analogous to standard electronics techniques.