Transmissive metasurface lens integration

Abstract

To provide transmissive metasurface lens integration.SOLUTION: Metasurface elements, integrated systems incorporating such metasurface elements with light sources and / or detectors, and methods of manufacturing and operating such optical arrangements and integrated systems are provided. Systems and methods for integrating transmissive metasurfaces with other semiconductor devices or additional metasurface elements, and more particularly to the integration of such metasurfaces with substrates, illumination sources, and sensors are also provided. The provided metasurface elements may be used to shape output light from an illumination source or collect light reflected from a scene to form two unique patterns using polarization of light. Shaped emission light and collection light may be integrated into a single co-designed probe and detection optical system.SELECTED DRAWING: None

Description

Technical Field

[0001] The present disclosure relates to an optical arrangement of a metasurface element, an integrated system integrating a light source and / or a detector with such a metasurface element, and a method of manufacturing such an optical arrangement and integrated system.

Background Art

[0002] A metasurface element is a diffractive optical system in which individual waveguide elements have a sub-wavelength spacing and have a planar shape. Metasurface elements have been recently developed for applications in the UV-IR band (300 - 10,000 nm). Compared to conventional refractive optical systems, metasurface elements abruptly introduce a phase shift into the bright field. This enables the metasurface element to have a thickness on the order of the wavelength of the light it is designed to operate with, while conventional refractive surfaces have a thickness 10 - 100 times (or more) larger than the wavelength of the light they are designed to operate with. Additionally, metasurface elements have no thickness variation in the components and can thus form light without bending, as required for refractive optical systems. Compared to conventional diffractive optical elements (DOEs), such as binary diffractive optical systems, metasurface elements have the ability to impart a range of phase shifts to the incident light field, and at a minimum, a metasurface element can have a phase shift between 0 and 2π with at least five different values from that range, while a binary DOE can only impart two different values of phase shift and is often limited to a phase shift of either 0 or 1π. Compared to a multi-level DOE, a metasurface element does not require variation in height along the optical axis of its components, and only the in-plane geometry of the metasurface element features varies.

Summary of the Invention

Problems to be Solved by the Invention

[0003] This application relates to an optical arrangement of a metasurface element, an integrated system integrating a light source and / or a detector with such a metasurface element, and a method of manufacturing such an optical arrangement and integrated system.

Means for Solving the Problems

[0004] Many embodiments relate to a method for fabricating one or more metasurface elements or systems, depositing a hard mask material layer on at least one surface of a substrate, the substrate being transparent over a specified operating bandwidth, depositing a pattern material layer on the hard mask material layer, patterning the pattern material to form an array pattern on the hard mask layer, the array pattern including either a positive or negative replica of an array of metasurface features, the array of metasurface features including a plurality of metasurface features having a feature size smaller than the wavelength of light within a specified operating bandwidth, and being configured to impose a phase shift on colliding light in the plane of the plurality of metasurface features, etching the hard mask layer using an anisotropic etching process to form a plurality of recessed and raised features corresponding to the array pattern within the hard mask, and removing any remaining pattern material from over the hard mask layer including.

[0005] In many other embodiments, the substrate is formed from a material selected from the group consisting of fused silica, sapphire, borosilicate glass, and rare earth oxide glass.

[0006] In still many other embodiments, the hard mask material layer is formed from a material selected from the group consisting of silicon, silicon nitride of various stoichiometries, silicon dioxide, titanium dioxide, and alumina, and is deposited using a deposition process selected from the group consisting of sputtering, chemical vapor deposition, and atomic layer deposition.

[0007] In still many other embodiments, the pattern material layer is formed from either photoresist patterning using a lithography process or polymer patterning using a nanoimprint method.

[0008] In still many other embodiments, the array pattern is etched using a reactive ion etching method selected from the group consisting of SF6, Cl2, BCl3, C4F8 or any static or multiple mixture thereof.

[0009] In yet still many other embodiments, the remaining pattern material is removed using a process selected from the group consisting of chemical solvents, chemical etchants, and plasma etchants.

[0010] In yet still many other embodiments, the patterned hard mask material is a dielectric and forms the meta-surface features of the meta-surface element.

[0011] In yet still many other embodiments, the method further comprises depositing a dielectric meta-surface material layer on the patterned hard mask material layer such that the meta-surface material layer fills the depressions within the hard mask material layer and spreads over the raised features of the hard mask material layer to form a vapor deposited layer of the meta-surface material on top of the hard mask layer, and planarizing the vapor deposited layer such that the meta-surface material layer and the hard mask layer end at a uniform height on the substrate.

[0012] In yet still many other embodiments, the meta-surface material layer is formed from a material selected from silicon, silicon nitride of various stoichiometries, silicon dioxide, titanium dioxide, alumina and is deposited using a conformal process selected from the group consisting of chemical vapor deposition and atomic layer deposition.

[0013] ​​In still many other embodiments, planarization uses an etching process selected from the group consisting of wet etching and plasma etching, or a process selected from chemical mechanical planarization techniques.

[0014] In still many other embodiments, the meta-surface material placed within the recess forms the meta-surface features of the meta-surface element, and the hard mask material is configured as an embedding material having a refractive index lower than that of the meta-surface material in a specified operating bandwidth.

[0015] In still many other embodiments, the hard mask material has very little absorption over a specified operating bandwidth and has a refractive index between about 1 and about 2.4 in the specified operating bandwidth.

[0016] In still many other embodiments, the method further includes using selective etching to remove the hard mask material layer such that the meta-surface material layer placed within the recesses of the patterned hard mask remains on the surface of the substrate after removal of the hard mask material layer, forming a plurality of separated meta-surface features separated by a plurality of voids.

[0017] In still many other embodiments, the method further includes depositing an embedding material layer on the separated meta-surface features such that the voids between the features are filled, thereby causing the embedding material layer to spread over the surface of the meta-surface material layer, and the embedding material layer has a refractive index lower than that of the meta-surface material in a specified operating bandwidth.

[0018] In still many other embodiments, the embedding material is a polymer selected from the group consisting of poly(methyl methacrylate), SU8, and benzocyclobutene.

[0019] In still many other embodiments, the embedding material is a solid film selected from the group consisting of silicon dioxide, aluminum oxide, titanium dioxide, silicon nitride, hafnium oxide, zinc oxide, and spin-on glass.

[0020] In still many other embodiments, the method further includes planarizing the embedding material layer such that the meta-surface material layer and the embedding material layer end at a uniform height on the substrate.

[0021] In still many other embodiments, the method further includes depositing an anti-reflection coating on one or both of the surfaces of the substrate disposed on the opposite side of the embedding material layer and the meta-surface element.

[0022] In still many other embodiments, the anti-reflection coating is composed of layers in which any combination of materials selected from the group consisting of silicon dioxide, titanium dioxide, aluminum oxide, silicon nitride, aluminum nitride, and amorphous silicon are alternately overlapped, and each of the alternately overlapped layers has a thickness less than the wavelength of light within the operating bandwidth.

[0023] In still many other embodiments, the substrate is either disposed on top of an illuminator or a sensor, or is itself an illuminator or a sensor.

[0024] In still many other embodiments, the substrate has a substrate thickness that is inappropriate for use with the target optical system and: removing at least a portion of the back side of the substrate through one or both of grinding or chemical etching, and aligning and fusing an additional substrate to the substrate of the meta-surface element further includes at least one of.

[0025] In still many other embodiments, the additional substrate itself has a metasurface element disposed on one of its surfaces, and the substrate and the additional substrate are fused along the surfaces opposite to the surfaces on which the relevant metasurface elements are disposed.

[0026] In still many other embodiments, the fusing method uses a bonding process having a thermal budget below 600 °C.

[0027] In still many other embodiments, the bonding process is a wafer bonding process using an adhesive selected from the group consisting of photoepoxy, benzocyclobutene, UV curable polymer, SU8, and plasma-activated silicon dioxide film.

[0028] In still many other embodiments, the method further includes removing at least a portion of the back side of one or both of the substrates before fusing.

[0029] In still many other embodiments, the method further includes forming at least a first metasurface element on a first surface of a first substrate, and forming at least a second metasurface element on a first surface of a second substrate, and fusing the first and second substrates together along the surfaces opposite to the first surfaces of the substrates using a bonding process having a thermal budget below 600 °C.

[0030] In still many other embodiments, the plurality of metasurface features are non-uniform.

[0031] In still many other embodiments, the plurality of metasurface features deviate from the ideal shape by an amount that can be determined in advance based on the dimensions of the metasurface features.

[0032] In still many other embodiments, the metasurface element is embedded and planarized and includes two layers of metasurface features that are offset from each other by a distance that is less than or on the same order as the wavelength of light within the specified operating bandwidth, such that the two layers of metasurface features operate in concert to impose a phase shift on the impinging light.

[0033] In still many other embodiments, the plurality of metasurface features are non-uniform and deviate from the ideal shape by a pre-determinable amount based on the dimensions of the metasurface features, the ideal shape being square, the ideal square having a side dimension that is less than 200 nm where the metasurface feature is formed as circular, and the ideal square having a side dimension that is less than 300 nm where the metasurface feature is formed as a square with rounded edges.

[0034] In still many other embodiments, the method further comprises forming a plurality of identical or unique first metasurface elements, providing a plurality of identical or unique illumination sources arranged in a planar array and integrating at least one of the plurality of first metasurface elements with each of the plurality of illumination sources in the array such that light from each of the plurality of illumination sources passes through at least one of the first metasurface elements, thereby imposing angular deflection, placing a first spacer layer between the planar array of illumination sources and the first metasurface elements, the first spacer layer being configured to cause divergence in the light emitted from each of the illumination sources in the planar array before it impinges on each of the first metasurface elements, placing a second metasurface element at a distance from the plurality of first metasurface elements, the second metasurface element being configured to imprint a far-field illumination pattern on the bright field formed by the combined emission of all of the plurality of illumination sources, and placing a second spacer layer between the first and second metasurface elements such that an offset distance is formed therebetween including

[0035] Various embodiments include forming at least a first metasurface element on a first surface of a first substrate, and forming at least a second metasurface element on a first surface of a second substrate, and fusing the first and second substrates together along a surface opposite the first surface of the substrate using a bonding process having a thermal budget below 600 °C, related to a method of forming a multi-metasurface element.

[0036] In various other embodiments, the bonding process is a wafer bonding process using an adhesive selected from the group consisting of photoepoxy, benzocyclobutene, UV curable polymer, SU8, and plasma activated silicon dioxide film.

[0037] In still various other embodiments, the method further includes removing at least a portion of the back side of one or both of the substrates before fusing.

[0038] In still various other embodiments, the method further embedding and planarizing at least one of the first and second metasurface elements, forming at least a third metasurface element on a first surface of a third substrate, and fusing a surface of the third substrate opposite the first surface to the planarized first or second metasurface using a bonding process having a thermal budget below 600 °C.

[0039] In yet still various other embodiments, planarizing further includes embedding at least one of the first and second metasurface elements in either a polymer or a solid bonding agent.

[0040] In yet still various other embodiments, the method further includes repeating the steps of forming, embedding, and fusing to form a layered stack of four or more metasurface elements.

[0041] Still further, in various other embodiments, at least one of the layers at one end of the layered stack is either an illuminator or a sensor.

[0042] Still further, in various other embodiments, the method further includes inserting a spacer substrate between the first and second substrate surfaces on opposite sides of the metasurface element, the spacer substrate having at least one opening disposed therethrough, and fusing the spacer substrate to the first and second substrates using a bonding process having a thermal budget below 600° C., such that at least one opening forms a void between the first and second substrates. Including.

[0043] Still further, in various other embodiments, the spacer substrate is formed of a low refractive index material selected from the group consisting of polymers, SiO2, and glass.

[0044] Still further, in various other embodiments, the spacer material is coated with black chrome.

[0045] Still further, in various other embodiments, the method further includes repeating the steps of forming, inserting, and fusing to form a layered stack of three or more metasurface elements.

[0046] Still further, in various other embodiments, at least one of the layers at one end of the layered stack is either an illuminator or a sensor.

[0047] Still further, in various other embodiments, the plurality of metasurface features are non-uniform.

[0048] Still further, in various other embodiments, the plurality of metasurface features deviate from the ideal shape by a pre-determinable amount based on the dimensions of the metasurface features.

[0049] Further embodiments include forming two layers of metasurface features on a substrate, the two layers being offset from each other by a distance less than or on the same order as the wavelength of light within a specified operating bandwidth, whereby the two layers of metasurface features operate in conjunction to impose a phase shift on the impinging light, relating to a method of forming a composite metasurface device.

[0050] Additional embodiments include forming a plurality of identical or unique first metasurface elements, providing a plurality of identical or unique illumination sources arranged in a planar array and integrating at least one of the plurality of first metasurface elements with each of the plurality of illumination sources in the array such that light from each of the plurality of illumination sources passes through at least one of the first metasurface elements, thereby causing angular deflection, placing a first spacer layer between the planar array of illumination sources and the first metasurface elements, the first spacer layer being configured to cause divergence in the light emitted from each of the illumination sources in the planar array before each impinges on a respective first metasurface element, placing a second metasurface element at a distance from the plurality of first metasurface elements, the second metasurface element being configured to imprint a far-field illumination pattern on the bright field formed by the emission of all of the plurality of illumination sources, and placing a second spacer layer between the first and second metasurface elements such that an offset distance is formed therebetween relating to a method of forming a metasurface device.

[0051] In yet further additional embodiments, at least the first spacer layer includes a solid material.

[0052] In yet further additional embodiments, at least the second spacer layer includes voids.

[0053] In still further additional other embodiments, the plurality of metasurface features are non-uniform.

[0054] In still further additional other embodiments, the plurality of metasurface features deviate from the ideal shape by an amount that can be pre-determined based on the dimensions of the metasurface features.

[0055] In yet still further additional other embodiments, the method further comprises forming a plurality of identical or unique first metasurface elements, providing a plurality of identical or unique sensor elements arranged in a planar array, integrating at least one of the plurality of first metasurface elements with each of the plurality of sensor elements in the array such that light impinging on each of the plurality of sensor elements passes through at least one of the first metasurface elements, thereby causing angular deflection, placing a first spacer layer between the planar array of sensor elements and the first metasurface elements, the first spacer layer being configured to cause divergence in the light impinging on each of the first metasurface elements before it impinges on each of the sensor elements of the planar array, placing a second metasurface element at a distance from the plurality of first metasurface elements, the second metasurface element being configured to imprint the far-field illumination pattern onto the bright field that it impinges on, and placing a second spacer layer between the first and second metasurface elements such that an offset distance is formed therebetween including.

[0056] Numerous other embodiments include forming a plurality of identical or unique first metasurface elements, Providing a plurality of identical or unique sensor elements arranged in a planar array and integrating at least one of a plurality of first metasurface elements with each of the plurality of sensor elements in the array such that light impinging on each of the plurality of sensor elements passes through at least one of the first metasurface elements, thereby imparting angular deflection. Placing a first spacer layer between the planar array of sensor elements and the first metasurface elements, the first spacer layer being configured to cause divergence in the light impinging on each of the first metasurface elements before it impinges on each of the sensor elements of the planar array. Placing a second metasurface element at a distance from the plurality of first metasurface elements, the second metasurface element being configured to imprint a far-field illumination pattern onto a bright field that it impinges on, and Placing a second spacer layer between the first and second metasurface elements such that an offset distance is formed therebetween relates to a method of forming a metasurface element including the above.

[0057] Some embodiments include an array of metasurface features disposed on a substrate having transmissivity over a specified operating bandwidth, the array including a plurality of metasurface features having a feature size smaller than the wavelength of light within the specified operating bandwidth, the plurality of metasurface features being configured to impose a phase shift on impinging light in the plane of the plurality of metasurface features. The plurality of metasurface features are non-uniform and deviate from an ideal shape by a pre-determinable amount based on the dimensions of the metasurface features. relates to a metasurface element.

[0058] In some other embodiments, the ideal shape is a square, and the ideal square has a side dimension smaller than 200 nm where the metasurface feature is formed as a circle, and the ideal square has a side dimension smaller than 300 nm where the metasurface feature is formed as a square with rounded edges.

[0059] Many embodiments include a plurality of identical or unique illumination sources or sensor elements arranged in a planar array, a first spacer layer disposed on the planar array of illumination sources and configured to cause divergence in the light emitted from each of the illumination sources in the planar array or convergence in the light impinging on each of the sensor elements, a plurality of identical or unique first metasurface elements disposed on the first spacer layer, wherein at least one of the plurality of first metasurface elements is associated with each of the plurality of illumination sources or sensor elements in the array such that light emitted from each of the plurality of illumination sources or impinging on each of the plurality of sensor elements passes through at least one of the first metasurface elements, thereby imparting angular deflection, a second metasurface element disposed at a distance from the plurality of first metasurface elements and configured to imprint a far-field illumination pattern onto a bright field that impinges thereon, and a second spacer layer between the first and second metasurface elements such that an offset distance is formed therebetween relating to an array of metasurface-corresponding illumination or sensors including.

[0060] In many other embodiments, the plurality of metasurface features on each of the metasurface elements are non-uniform and deviate from the ideal shape by a pre-determinable amount based on the dimensions of the metasurface features.

[0061] In still many other embodiments, at least a plurality of metasurface features on the first or second metasurface element are configured to have an asymmetric cross-section and are arranged at at least two different rotation angles, such that the metasurface element imprints at least two patterns having orthogonal polarization and linearly offset from each other on an illumination source, or is configured to detect such patterns from incident light before irradiation of a sensor element, and the arrangement is configured such that three-dimensional information is acquired from a scene in a single shot by the arrangement.

[0062] In still many other embodiments, the illumination source is either polarized or non-polarized and is selected from the group consisting of a VCSEL, a solid-state laser, a quantum cascade laser, an LED, and a superluminescent LED.

[0063] In yet still many other embodiments, the two patterns are unique.

[0064] In yet still many other embodiments, the two patterns have at least 50,000 junction points.

[0065] In yet still many other embodiments, at least the first pattern is configured to acquire a measurement of the foreground of a scene and at least the second pattern is configured to acquire a measurement of the background of a scene.

[0066] In yet still many other embodiments, the two patterns are diagonally polarized with respect to the laser polarization.

[0067] In yet still many other embodiments, three or more patterns having three or more different polarizations are used.

[0068] Various embodiments include at least one sensor element, At least one first and at least one second metasurface element disposed with an offset distance on at least one sensor element, including at least one first and second metasurface element having a first spacer layer disposed therebetween. Each of the at least one first and second metasurface elements includes an array of metasurface features disposed on at least one substrate having translucency over a specified operating bandwidth, the array including a plurality of metasurface features having a feature size smaller than the wavelength of light within the specified operating bandwidth, and configured to impose a phase shift on incident light in the plane of the plurality of metasurface features. The array of metasurface features on each of the at least one first and second metasurface elements is configured to collect light of the specified operating bandwidth over a specified field of view and shift the incident light so that it impinges on the sensor element at a critical ray angle of zero degrees or close to zero degrees. Relates to a metasurface element corresponding sensor.

[0069] In various other embodiments, the first spacer layer is either a solid spacer material or a void.

[0070] In still various other embodiments, the field of view is ±44 degrees.

[0071] In still various other embodiments, the sensor further includes a narrowband optical filter disposed between the metasurface element and the sensor element.

[0072] In yet still various other embodiments, the narrowband optical filter is composed of alternating overlapping layers having low and high refractive indices selected from the group consisting of silicon dioxide, titanium dioxide, amorphous silicon, silicon nitride, and aluminum oxide.

[0073] In still yet various other embodiments, the sensor further includes a plurality of identical microlenses disposed between the metasurface element and the sensor element.

[0074] In still yet various other embodiments, at least one first metasurface element and at least one second metasurface element are disposed on opposite sides of the same substrate, and the substrate includes a first spacer layer.

[0075] In still yet various other embodiments, two metasurface elements on both sides of the substrate have the same height.

[0076] In still yet various other embodiments, two metasurface elements are formed from films simultaneously deposited on the front and back of the same substrate using a conformal deposition process selected from the group consisting of pressure chemical vapor deposition and atomic layer vapor deposition.

[0077] In still yet various other embodiments, at least one first metasurface element and at least one second metasurface element are disposed facing inward toward each other on separate substrates separated by a void.

[0078] In still yet various other embodiments, the sensor further includes an optical bandpass filter incorporated on the outward-facing surface of at least one second metasurface substrate.

[0079] In still yet various other embodiments, the sensor further includes at least a third metasurface element disposed between the first and second metasurface elements and the CMOS sensor and configured to angularly branch the path of the incident light so that the light impinging on the CMOS sensor has a non-zero chief ray angle.

[0080] In still yet various other embodiments, at least three metasurfaces are configured to minimize lattice distortion to less than 5% across a specified field of view.

[0081] In still further various other embodiments, the sensor element is a CMOS sensor.

[0082] Further embodiments include at least one sensor element and at least one illumination source, at least one separate metasurface element having an offset distance placed on each of the at least one sensor element and the at least one illumination source and having at least one spacer layer associated with each respectively, including each of the metasurface elements includes an array of metasurface features disposed on a substrate having translucency over a specified operating bandwidth, the array includes a plurality of metasurface features having a feature size smaller than the wavelength of light within the specified operating bandwidth, at least one illumination metasurface element disposed in association with the illumination source is configured to impose a radiation pattern on the bright field emitted therefrom within the plane of the plurality of metasurface features, and at least one sensor metasurface element disposed in association with the at least one sensor element is configured to detect the radiation pattern of the bright field after illumination of the scene. Relates to a single platform imaging / detection system for metasurface element correspondence.

[0083] In still further embodiments, the system further includes a plurality of separate metasurface elements and spacer layers associated with each of the illumination source and the sensor element.

[0084] In still further embodiments, the metasurface element associated with the illumination source imprints two orthogonal polarizations on the bright field to generate at least two patterns having orthogonal polarizations and linearly offset from each other on the bright field to illuminate the scene, and the metasurface element associated with the sensor element is configured to detect at least two patterns so that three-dimensional information about the scene can be collected.

[0085] Numerous embodiments include Calculating the far field of the illumination source, Calculating the far field of an object, where the object is a metasurface element, Calculating a least squares fit to the far field of the object to obtain a pseudo far field, thereby resulting in the far field of the object by convolution of the pseudo far field and the far field of the illumination source, Setting an initial metasurface feature array grid and phase to an initial state, Determining one or more target cost functions and calculating a gradient function for each of the one or more cost functions for each of a plurality of pixels of the metasurface element, Inputting the results from the one or more cost functions and gradient functions into an optimization algorithm, Updating the phase for each of the plurality of pixels of the metasurface element and repeating the gradient calculation and optimization until the target cost function converges, and Outputting the calculated metasurface element phase profile Relates to a method for fabricating a metasurface element for imprinting a desired far field intensity on an illumination source, including.

[0086] In a number of other embodiments, the cost function is selected from the group consisting of the squared distance from the object, the nearest neighbor distance, the squared error of the far field projection of the metasurface element under illumination, and the smoothness of the calculated far field.

[0087] In yet a number of other embodiments, the optimization algorithm is either conjugate gradient or L-Broyden-Fletcher-Goldfarb-Shannon.

[0088] Some embodiments also relate to a method of forming a metasurface element on a substrate having a plurality of metasurface features having a feature size smaller than the wavelength of light within a specified operating bandwidth, the substrate being configured to impose a phase shift on colliding light in the plane of the plurality of metasurface features, the substrate having a substrate thickness inappropriate for use with the optical system of the object, and the following: Removing at least a portion of the back side of the substrate through one or both of grinding or chemical etching, and Aligning and fusing an additional substrate to the substrate of the meta-surface element further includes at least one of.

[0089] In some other embodiments, the additional substrate itself has a meta-surface element disposed on one of its surfaces, and the substrate and the additional substrate are fused along surfaces on opposite sides of the surface on which the associated meta-surface element is disposed.

[0090] In still some other embodiments, the fusing method uses a bonding process having a thermal budget below 600°C.

[0091] In still some other embodiments, the bonding process is a wafer bonding process that uses an adhesive selected from the group consisting of photoepoxy, benzocyclobutene, UV-curable polymer, SU8, and plasma-activated silicon dioxide film.

[0092] In still yet some other embodiments, the method further includes removing at least a portion of the back side of one or both of the substrates prior to fusing.

[0093] In still yet some other embodiments, the method further includes forming at least a first meta-surface element on a first surface of a first substrate, and forming at least a second meta-surface element on a first surface of a second substrate, and fusing the first and second substrates together along surfaces on opposite sides of the first surface of the substrate using a bonding process having a thermal budget below 600°C.

[0094] In still yet some other embodiments, the plurality of meta-surface features are non-uniform.

[0095] In still some other embodiments, the plurality of metasurface features deviate from the ideal shape by an amount that can be pre-determined based on the dimensions of the metasurface features.

[0096] In still some other embodiments, the method further includes embedding and planarizing at least one of the first and second metasurface elements, forming at least a third metasurface element on a first surface of a third substrate, and fusing a surface of the third substrate opposite the first surface to the planarized first or second metasurface using a bonding process having a thermal budget below 600°C.

[0097] In still some other embodiments, planarizing further includes embedding at least one of the first and second metasurface elements in either a polymer or a solid bonding agent.

[0098] In still some other embodiments, forming, embedding, and fusing steps are repeated to form a layered stack of four or more metasurface elements.

[0099] In still some other embodiments, at least one of the layers at one end of the layered stack is either an illuminator or a sensor.

[0100] In still some other embodiments, the method further includes inserting a spacer substrate between the surfaces of the first and second substrates opposite the metasurface elements, the spacer substrate having at least one opening therethrough, and fusing the spacer substrate to the first and second substrates using a bonding process having a thermal budget below 600°C such that at least one opening forms a gap between the first and second substrates. including.

[0101] A number of other embodiments are an array of metasurface features disposed on a substrate having translucency over a specified operating bandwidth, the array including a plurality of metasurface features having a feature size smaller than the wavelength of light within the specified operating bandwidth, and configured to impose a phase shift on colliding light in the plane of the plurality of metasurface features, the plurality of metasurface features being amorphous Si metasurface features embedded in SiO2 and having a pillar height of 500 - 1000 nm and a pillar diameter of 100 - 300 nm, amorphous Si metasurface features embedded in SiO2 and having a pillar height of 600 nm and a pillar diameter of 100 - 300 nm, amorphous Si metasurface features having voids disposed therebetween and having a pillar height of 1 - 500 nm and a pillar diameter of 100 - 350 nm, amorphous Si metasurface features having voids disposed therebetween and having a pillar height starting from 480 nm and a pillar diameter of 100 - 280 nm, TiO2 metasurface features having voids disposed therebetween and having a pillar height of 300 - 1000 nm and a pillar diameter of 100 - 350 nm, TiO2 metasurface features having voids disposed therebetween and having a pillar height of 975 nm and a pillar diameter of 100 - 300 nm, amorphous Si metasurface features embedded in benzocyclobutane and having a pillar height of 590 nm and a pillar diameter of 100 - 300 nm, amorphous Si metasurface features embedded in SiO2 and having a pillar height of 600 nm and a pillar diameter of 100 - 275 nm, amorphous Si metasurface features embedded in SU8 and having a pillar height of 675 nm and a pillar diameter of 100 - 300 nm, as well as amorphous Si metasurface features in air having a pillar height of 600 nm and a pillar diameter of 100 - 300 nm with an element pitch of 450 nm Comprising an array of metasurface features formed from one of the group consisting of, Relates to a metasurface element.

[0102] In many other embodiments where amorphous Si is the material of choice, the amorphous Si is hydrogenated and can have high light transmission compared to amorphous silicon in which hydrogen is not present in the structure.

[0103] Additional embodiments and features are described in part in the following description, in part will become apparent to those skilled in the art upon examination of this specification, or may be learned by practice of the present disclosure. A further understanding of the nature and advantages of the present disclosure can be realized by reference to the remaining portions of this specification and the drawings which form a part of this disclosure. The present invention provides, for example, the following. (Item 1) A method for fabricating one or more metasurface elements or systems, Depositing a hard mask material layer on at least one side of a substrate, wherein the substrate has light transmissivity over a specified operating bandwidth, Depositing a pattern material layer on the hard mask material layer, Patternizing the pattern material to form an array pattern on the hard mask layer, the array pattern including either a positive or negative replica of an array of metasurface features, the metasurface feature array including a plurality of metasurface features having a feature size smaller than the wavelength of light within the specified operating bandwidth, and configured to impose a phase shift on colliding light in the plane of the plurality of metasurface features, Etching the hard mask layer using an anisotropic etching process to form a plurality of depressions and raised features corresponding to the array pattern within the hard mask, Removing any remaining pattern material from on top of the hard mask layer And a method. (Item 2) The substrate is formed from a material selected from the group consisting of fused quartz, sapphire, borosilicate glass, and rare earth oxide glass. The hard mask material layer is formed from a material selected from the group consisting of silicon, silicon nitride of various stoichiometries, silicon dioxide, titanium dioxide, and alumina, and is disposed using a deposition process selected from the group consisting of sputtering, chemical vapor deposition, and atomic layer deposition. The pattern material layer is formed from either photoresist patterning using a lithography process or polymer patterning using a nanoimprint method. The array pattern is etched using a reactive ion etching method selected from the group consisting of SF6, Cl2, BCl3, C4F8, or any static or multiple mixture. The remaining pattern material is removed using a process selected from the group consisting of chemical solvents, chemical etching solutions, and plasma etching solutions. The method according to item 1. (Item 3) The method according to item 1, wherein the patterned hard mask material is a dielectric and forms the meta-surface features of the meta-surface element. (Item 4) Depositing a dielectric meta-surface material layer on the patterned hard mask material layer such that the meta-surface material layer fills the depressions within the hard mask material layer and spreads over the raised features of the hard mask material layer to form a vapor deposition layer of the meta-surface material on the hard mask layer; Planarizing the vapor deposition layer such that the meta-surface material layer and the hard mask layer end at a uniform height on the substrate. The method according to item 1, further comprising the above steps. (Item 5) The meta - surface material layer is formed from a material selected from silicon, silicon nitride of various stoichiometries, silicon dioxide, titanium dioxide, and alumina, and is deposited using a conformal process selected from the group consisting of chemical vapor deposition and atomic layer deposition. The planarization uses an etching process selected from the group consisting of wet etching and plasma etching, or a process selected from chemical - mechanical planarization techniques. The method according to item 4. (Item 6) The method according to item 4, wherein the meta - surface material placed within the recess forms the meta - surface features of the meta - surface element, and the hard - mask material is configured as an embedding material having a refractive index lower than that of the meta - surface material in the specified operating bandwidth. (Item 7) The method according to item 6, wherein the hard - mask material has very little absorption over the specified operating bandwidth and has a refractive index between about 1 and about 2.4 in the specified operating bandwidth. (Item 8) Removing the hard - mask material layer using selective etching such that the meta - surface material layer placed within the recess of the patterned hard - mask remains on the surface of the substrate after removal of the hard - mask material layer, forming a plurality of separated meta - surface features separated by a plurality of voids. The method according to item 4, further comprising. (Item 9) The method according to item 8, further comprising depositing an embedding material layer over the separated meta - surface features such that the voids between the features are filled, thereby causing the embedding material layer to spread over the surface of the meta - surface material layer, and the embedding material layer has a refractive index lower than that of the meta - surface material in the specified operating bandwidth. (Item 10) The method according to item 9, wherein the embedding material is a polymer selected from the group consisting of poly(methyl methacrylate), SU8, and benzocyclobutene. (Item 11) The method according to item 9, wherein the embedding material is a solid film selected from the group consisting of silicon dioxide, aluminum oxide, titanium dioxide, silicon nitride, hafnium oxide, zinc oxide, and spin-on glass. (Item 12) The method according to item 9, further comprising planarizing the embedding material layer such that the meta-surface material layer and the embedding material layer end at a uniform height on the substrate. (Item 13) The method according to item 12, further comprising depositing an antireflection coating on one or both of the surfaces of the substrate disposed on the opposite side of the embedding material layer and the meta-surface element. (Item 14) The method according to item 13, wherein the antireflection coating is composed of layers in which any combination of materials selected from the group consisting of silicon dioxide, titanium dioxide, aluminum oxide, silicon nitride, aluminum nitride, and amorphous silicon are alternately overlapped, and each of the alternately overlapped layers has a thickness less than the wavelength of light within the operating bandwidth. (Item 15) The method according to item 1, wherein the substrate is disposed on a luminaire or a sensor, or is itself a luminaire or a sensor. (Item 16) The substrate has a substrate thickness inappropriate for use with the optical system of interest and: removing at least a part of the back side of the substrate through one or both of grinding or chemical etching, and aligning and fusing an additional substrate to the substrate of the meta-surface element The method according to item 1, further comprising at least one of the above. (Item 17) The additional substrate itself has a meta-surface element disposed on one of its surfaces, and the substrate and the additional substrate are fused along the surfaces on the opposite side of the surface on which the associated meta-surface element is disposed. The method according to item 16. (Item 18) The method of fusion uses a bonding process having a thermal budget below 600°C, the method according to item 16. (Item 19) The bonding process is a wafer bonding process using an adhesive selected from the group of photoepoxy, benzocyclobutene, UV-curable polymer, SU8, and plasma-activated silicon dioxide film, the method according to item 18. (Item 20) The method according to item 18 further includes removing at least a part of the back side of one or both of the substrates before fusion. (Item 21) The method according to item 1 further includes forming at least a first metasurface element on a first surface of a first substrate, forming at least a second metasurface element on a first surface of a second substrate, and fusing the first and second substrates together along a surface opposite to the first surface of the substrate using a bonding process having a thermal budget below 600°C. (Item 22) The method according to item 1, wherein the plurality of metasurface features are non-uniform. (Item 23) The method according to item 1, wherein the plurality of metasurface features deviate from an ideal shape by an amount that can be determined in advance based on the dimensions of the metasurface features. (Item 24) A method of forming a multi-metasurface element includes forming at least a first metasurface element on a first surface of a first substrate, forming at least a second metasurface element on a first surface of a second substrate, and fusing the first and second substrates together along a surface opposite to the first surface of the substrate using a bonding process having a thermal budget below 600°C. (Item 25) The method according to item 24, wherein the bonding process is a wafer bonding process using an adhesive selected from the group consisting of an optical epoxy, benzocyclobutene, a UV curable polymer, SU8, and a plasma activated silicon dioxide film. (Item 26) The method according to item 24, further comprising removing at least a portion of the back side of one or both of the substrates before fusion. (Item 27) Embedding and planarizing at least one of the first and second metasurface elements; Forming at least a third metasurface element on a first surface of a third substrate; Fusing the surface of the third substrate opposite the first surface to the planarized first or second metasurface using a bonding process having a thermal budget below 600 °C; The method according to item 24, further comprising the above steps. (Item 28) The method according to item 27, wherein the planarization further comprises embedding at least one of the first and second metasurface elements in either a polymer or a solid bonding agent. (Item 29) The method according to item 27, comprising repeating the steps of forming, embedding, and fusing to form a layered stack of four or more metasurface elements. (Item 30) The method according to item 29, wherein at least one of the layers at one end of the layered stack is either an illuminator or a sensor. (Item 31) Inserting a spacer substrate between the surfaces of the first and second substrates on the opposite sides of the metasurface element, the spacer substrate having at least one opening disposed therethrough; Fusing the spacer substrate to the first and second substrates using a bonding process having a thermal budget below 600 °C such that the at least one opening forms a void between the first and second substrates; The method according to item 24, further comprising (Item 32) The method according to item 31, wherein the spacer substrate is formed of a low refractive index material selected from the group consisting of polymer, SiO2, and glass. (Item 33) The method according to item 32, wherein the spacer material is coated with black chrome. (Item 34) The method according to item 31, further comprising repeatedly performing the steps of forming, inserting, and fusing to form a layered stack of three or more meta-surface elements. (Item 35) The method according to item 24, wherein at least one of the layers at one end of the layered stack is either an illuminator or a sensor. (Item 36) The method according to item 24, wherein the plurality of meta-surface features are non-uniform. (Item 37) The method according to item 24, wherein the plurality of meta-surface features deviate from the ideal shape by an amount that can be determined in advance based on the dimensions of the meta-surface features. (Item 38) The method according to item 1, wherein the meta-surface elements are embedded and planarized, and include two layers of meta-surface features offset from each other by a distance smaller than or of the same order as the wavelength of the light within the specified operating bandwidth, whereby the two layers of meta-surface features operate in conjunction to impose a phase shift on the colliding light. (Item 39) A method of forming a composite meta-surface element, comprising forming two layers of meta-surface features on a substrate, the two layers being offset from each other by a distance smaller than or of the same order as the wavelength of the light within the specified operating bandwidth, whereby the two layers of meta-surface features operate in conjunction to impose a phase shift on the colliding light. (Item 40) The plurality of metasurface features are non-uniform and deviate from the ideal shape by a pre-determinable amount based on the dimensions of the metasurface features, the ideal shape being square, the ideal square having a side dimension smaller than 200 nm in which the metasurface features are formed as circular, and the ideal square having a side dimension smaller than 300 nm in which the metasurface features are formed as a square with rounded edges, the method according to item 1. (Item 41) Forming a plurality of identical or unique first metasurface elements; Providing a plurality of identical or unique illumination sources arranged in a planar array and integrating at least one of the plurality of first metasurface elements with each of the plurality of illumination sources within the array such that light from each of the plurality of illumination sources passes through at least one of the first metasurface elements, thereby applying angular deflection; Placing the first spacer layer between the planar array of illumination sources and the first metasurface elements, the first spacer layer being configured to cause divergence in the light emitted from each of the illumination sources of the planar array before it impinges on each of the first metasurface elements; Placing the second metasurface element at a distance from the plurality of first metasurface elements, the second metasurface element being configured to imprint a far-field illumination pattern in the bright field formed by the emission of all of the plurality of illumination sources; Placing a second spacer layer between the first and second metasurface elements such that an offset distance is formed therebetween; Further comprising the method according to item 1. (Item 42) Forming a plurality of identical or unique first metasurface elements; Providing a plurality of identical or unique illumination sources arranged in a planar array and integrating at least one of the plurality of first metasurface elements with each of the plurality of illumination sources within the array such that light from each of the plurality of illumination sources passes through at least one of the first metasurface elements, thereby causing angular deflection; Arranging the first spacer layer between the planar array of illumination sources and the first metasurface element, wherein the first spacer layer is configured to cause divergence in the light emitted from each of the illumination sources of the planar array before impinging on each of the first metasurface elements; Arranging the second metasurface element at a distance from the plurality of first metasurface elements, wherein the second metasurface element is configured to imprint a far-field illumination pattern on the bright field formed by the emission of all of the plurality of illumination sources; Arranging a second spacer layer between the first and second metasurface elements such that an offset distance is formed therebetween; A method of forming a metasurface element, comprising: (Item 43) The method according to item 42, wherein at least the first spacer layer comprises a solid material. (Item 44) The method according to item 42, wherein at least the second spacer layer comprises voids. (Item 45) The method according to item 42, wherein the plurality of metasurface features are non-uniform. (Item 46) The method according to item 42, wherein the plurality of metasurface features deviate from an ideal shape by an amount that can be pre-determined based on the dimensions of the metasurface features. (Item 47) Forming a plurality of identical or unique first metasurface elements; Providing a plurality of identical or unique sensor elements arranged in a planar array, integrating at least one of the plurality of first metasurface elements with each of the plurality of sensor elements within the array, such that light impinging on each of the plurality of sensor elements passes through at least one of the first metasurface elements, thereby causing angular deflection; Disposing a first spacer layer between the planar array of sensor elements and the first metasurface elements, the first spacer layer being configured to cause divergence in the light impinging on each of the first metasurface elements before impinging on the respective sensor elements of the planar array; Disposing a second metasurface element at a distance from the plurality of first metasurface elements, the second metasurface element being configured to imprint a far-field illumination pattern onto a bright field; Disposing a second spacer layer between the first and second metasurface elements, thereby forming an offset distance therebetween; The method according to item 1, further comprising. (Item 48) Forming a plurality of identical or unique first metasurface elements; Providing a plurality of identical or unique sensor elements arranged in a planar array, integrating at least one of the plurality of first metasurface elements with each of the plurality of sensor elements within the array, such that light impinging on each of the plurality of sensor elements passes through at least one of the first metasurface elements, thereby causing angular deflection; Disposing a first spacer layer between the planar array of sensor elements and the first metasurface elements, the first spacer layer being configured to cause divergence in the light impinging on each of the first metasurface elements before impinging on the respective sensor elements of the planar array; Placing the second metasurface element at a distance from the plurality of first metasurface elements, wherein the second metasurface element is configured to imprint a far-field illumination pattern onto a bright field that collides therewith, Placing a second spacer layer between the first and second metasurface elements such that an offset distance is formed therebetween A method of forming a metasurface element, comprising: (Item 49) An array of metasurface features disposed on a substrate having light transmissivity over a specified operating bandwidth, the array including a plurality of metasurface features having a feature size smaller than the wavelength of light within the specified operating bandwidth, and configured to impose a phase shift on colliding light in the plane of the plurality of metasurface features. The plurality of metasurface features are non-uniform and deviate from an ideal shape by a pre-determinable amount based on the dimensions of the metasurface features. A metasurface element. (Item 50) The ideal shape is a square, the ideal square having a side dimension smaller than 200 nm in which the metasurface feature is formed as a circle, and the ideal square having a side dimension smaller than 300 nm in which the metasurface feature is formed as a square having a rounded edge, according to the method of item 49. (Item 51) A plurality of identical or unique illumination sources or sensor elements arranged in a planar array, A first spacer layer disposed above the planar array of illumination sources and configured to cause divergence in the light emitted from each of the illumination sources of the planar array or convergence in the light colliding with each of the sensor elements. A plurality of identical or unique first metasurface elements disposed on the first spacer layer, wherein at least one of the plurality of first metasurface elements is associated with each of the plurality of illumination sources or sensor elements in the array, such that light emitted from each of the plurality of illumination sources or impinging on each of the plurality of sensor elements passes through at least one of the first metasurface elements, thereby causing angular deflection, a plurality of identical or unique first metasurface elements; A second metasurface element disposed at a distance from the plurality of first metasurface elements, the second metasurface element being configured to imprint a bright field that impinges on a far-field illumination pattern, a second metasurface element; A second spacer layer between the first and second metasurface elements such that an offset distance is formed therebetween An array of metasurface-corresponding illumination or sensors including (Item 52) The plurality of metasurface features on each of the metasurface elements are non-uniform and deviate from an ideal shape by a pre-determinable amount based on the dimensions of the metasurface features, the illumination or sensor array according to item 51. (Item 53) The plurality of metasurface features on at least the first or second metasurface element are configured to have an asymmetric cross-section and are arranged at at least two different rotational angles such that the metasurface element imprints at least two patterns having orthogonal polarization and linearly offset from each other on the illumination source or, prior to irradiation of the sensor element, is configured to detect such patterns from the impinging light, the array being configured such that three-dimensional information is acquired from a scene in a single shot by the array, the illumination or sensor array according to item 51. (Item 54) The illumination source is polarized or non-polarized and is selected from the group consisting of VCSELs, solid state lasers, quantum cascade lasers, LEDs, and superluminescent LEDs, for the illumination or sensor array of item 53. (Item 55) The two patterns are unique, for the illumination or sensor array of item 53. (Item 56) The two patterns have at least 50,000 bonding points, for the illumination or sensor array of item 53. (Item 57) At least the first pattern is configured to obtain a measurement of the foreground of the scene, and at least the second pattern is configured to obtain a measurement of the background of the scene, for the illumination or sensor array of item 53. (Item 58) The two patterns are diagonally polarized with respect to the laser polarization, for the illumination or sensor array of item 53. (Item 59) Three or more patterns having three or more different polarizations are used, for the illumination or sensor array of item 53. (Item 60) At least one sensor element, At least one first and at least one second metasurface element disposed with an offset distance on the at least one sensor element, having a first spacer layer disposed therebetween, the at least one first and at least one second metasurface element comprising, Each of the at least one first and second metasurface elements includes an array of metasurface features disposed on at least one substrate having transparency over a specified operating bandwidth, the array including a plurality of metasurface features having a feature size smaller than the wavelength of light within the specified operating bandwidth, configured to impose a phase shift on incident light in the plane of the plurality of metasurface features, The arrangement of the metasurface features on each of the at least one first and second metasurface elements is configured to collect light within a specified operating bandwidth over a specified field of view and to shift the incident light such that it impinges on the sensor element at a principal ray angle of zero degrees or close to zero degrees. Metasurface element corresponding sensor. (Item 61) The sensor according to item 60, wherein the first spacer layer is either a solid spacer material or a void. (Item 62) The sensor according to item 60, wherein the field of view is ±44 degrees. (Item 63) The sensor according to item 60, further comprising a narrowband optical filter disposed between the metasurface element and the sensor element. (Item 64) The sensor according to item 60, wherein the narrowband optical filter is composed of alternating overlapping layers having low and high refractive indices selected from the group consisting of silicon dioxide, titanium dioxide, amorphous silicon, silicon nitride, and aluminum oxide. (Item 65) The sensor according to item 60, further comprising a plurality of identical microlenses disposed between the metasurface element and the sensor element. (Item 66) The sensor according to item 60, wherein the at least one first metasurface element and the at least one second metasurface element are disposed on opposite sides of the same substrate, and the substrate includes the first spacer layer. (Item 67) The sensor according to item 60, wherein the two metasurface elements on both sides of the substrate have the same height. (Item 68) The sensor according to item 60, wherein the two metasurface elements are formed from films simultaneously deposited on the front and back surfaces of the same substrate using a conformal deposition process selected from the group consisting of plasma-enhanced chemical vapor deposition and atomic layer deposition. (Item 69) The sensor according to item 60, wherein the at least one first metasurface element and the at least one second metasurface element are arranged facing inward toward each other on separate substrates separated by a gap. (Item 70) The sensor according to item 69, further comprising an optical bandpass filter incorporated in the outer-facing surface of the substrate of the at least one second metasurface. (Item 71) The sensor according to item 60, further comprising at least a third metasurface element arranged between the first and second metasurface elements and the CMOS sensor to angularly branch the path of the incident light so that the light impinging on the CMOS sensor has a non-zero chief ray angle. (Item 72) The sensor according to item 72, wherein the at least three metasurfaces are configured to minimize lattice distortion to less than 5% over the specified field of view. (Item 73) The sensor according to item 60, wherein the sensor element is a CMOS sensor. (Item 74) At least one sensor element and at least one illumination source, At least one separate metasurface element having an offset distance placed on each of the at least one sensor element and the at least one illumination source and having at least one spacer layer associated with each respectively, Including Each of the meta - surface elements includes an array of meta - surface features disposed on a substrate having translucency over a specified operating bandwidth, the array including a plurality of meta - surface features having a feature size smaller than the wavelength of light within the specified operating bandwidth, the at least one illumination meta - surface element disposed in association with the illumination source is configured to impose a radiation pattern on the bright - field emitted therefrom within the plane of the plurality of meta - surface features, and the at least one sensor meta - surface element disposed in association with the at least one sensor element is configured to detect the radiation pattern of the bright - field after irradiation of the scene. Single - platform imaging / detection system for meta - surface element correspondence. (Item 75) The system according to item 74, further comprising a plurality of distinct meta - surface elements and spacer layers associated with each of the illumination source and the sensor element. (Item 76) The meta - surface element associated with the illumination source imprints two orthogonal polarizations on the bright - field to generate at least two patterns having orthogonal polarizations and linearly offset from each other on the bright - field to irradiate the scene, and the meta - surface element associated with the sensor element is configured to detect the at least two patterns so as to collect three - dimensional information about the scene. The system according to item 74. (Item 77) Calculating an illumination source far - field view; Calculating a target far - field view, wherein the target is a meta - surface element; Calculating a least - squares fit to the target far - field view to obtain a pseudo - far - field view, thereby resulting in the target far - field view by convolution of the pseudo - far - field view and the illumination source far - field view; Setting an initial meta - surface feature array lattice and phase to an initial state; Determine one or more target cost functions and calculate a gradient function for each of the one or more cost functions for each of the plurality of pixels of the meta-surface element; Input the results from the one or more cost functions and the gradient function into an optimization algorithm; Update the phase for each of the plurality of pixels of the meta-surface element and repeat the gradient calculation and optimization until the target cost function converges; Output the calculated meta-surface element phase profile; A method for fabricating a meta-surface element for imprinting a desired far-field intensity on an illumination source, comprising: (Item 78) The method according to item 77, wherein the cost function is selected from the group consisting of the squared distance from the target, the nearest neighbor distance, the squared error of the far-field projection of the meta-surface element under illumination, and the smoothness of the calculated far-field. (Item 79) The method according to item 77, wherein the optimization algorithm is either conjugate gradient or L-Broyden-Fletcher-Goldfarb-Shannon. (Item 80) A method of forming a meta-surface element on a substrate that includes a plurality of meta-surface features having a feature size smaller than the wavelength of light within the specified operating bandwidth, and is configured to impose a phase shift on the colliding light in the plane of the plurality of meta-surface features, the substrate having a substrate thickness that is inappropriate for use with the optical system of the target, and further comprising at least one of: Removing at least a portion of the back side of the substrate through one or both of grinding or chemical etching; and Aligning and fusing an additional substrate to the substrate of the meta-surface element. The method further comprising at least one of the above. (Item 81) The additional substrate itself has a metasurface element disposed on one of its surfaces, and the substrate and the additional substrate are fused along the surface opposite to the surface on which the associated metasurface element is disposed, according to the method of item 80. (Item 82) The method of fusion uses a bonding process having a thermal budget below 600°C, according to the method of item 80. (Item 83) The bonding process is a wafer bonding process using an adhesive selected from the group of photoepoxy, benzocyclobutene, UV-curable polymer, SU8, and plasma-activated silicon dioxide film, according to the method of item 82. (Item 84) The method of item 82 further includes removing at least a part of the back side of one or both of the substrates before fusion. (Item 85) The method of item 80 further includes forming at least a first metasurface element on a first surface of a first substrate, forming at least a second metasurface element on a first surface of a second substrate, and fusing the first and second substrates together along the surface opposite to the first surface of the substrates using a bonding process having a thermal budget below 600°C. (Item 86) The plurality of metasurface features are non-uniform, according to the method of item 80. (Item 87) The plurality of metasurface features deviate from the ideal shape by an amount that can be determined in advance based on the dimensions of the metasurface features, according to the method of item 80. (Item 88) Embedding and planarizing at least one of the first and second metasurface elements, forming at least a third metasurface element on a first surface of a third substrate, Fusing the surface of the third substrate on the opposite side of the first surface to the planarized first or second metasurface using a bonding process having a thermal budget below 600 °C The method according to item 85, further comprising. (Item 89) The method according to item 88, wherein the planarization further comprises embedding at least one of the first and second metasurface elements in either a polymer or a solid bonding agent. (Item 90) The method according to item 88, comprising repeatedly performing the steps of forming, embedding, and fusing to form a layered stack of four or more metasurface elements. (Item 91) The method according to item 90, wherein at least one of the layers at one end of the layered stack is either an illuminator or a sensor. (Item 92) Inserting a spacer substrate between the surfaces of the first and second substrates on the opposite side of the metasurface element, the spacer substrate having at least one opening disposed therethrough, Fusing the spacer substrate to the first and second substrates using a bonding process having a thermal budget below 600 °C such that the at least one opening forms a gap between the first and second substrates The method according to item 88, further comprising. (Item 93) An array of metasurface features disposed on a substrate having light transmissivity over a specified operating bandwidth, the array comprising a plurality of metasurface features having a feature size smaller than the wavelength of light within the specified operating bandwidth, configured to impose a phase shift on colliding light in the plane of the plurality of metasurface features, and the plurality of metasurface features are Amorphous Si metasurface features embedded in SiO2 and having a pillar height of 500 - 1000 nm and a pillar diameter of 100 - 300 nm, An amorphous Si metasurface feature embedded in SiO₂ and having a pillar height of 600 nm and a pillar diameter of 100 - 300 nm, An amorphous Si metasurface feature having voids disposed therebetween and having a pillar height of 1 - 500 nm and a pillar diameter of 100 - 350 nm, An amorphous Si metasurface feature having voids disposed therebetween and having a pillar height starting from 480 nm and a pillar diameter of 100 - 280 nm, A TiO₂ metasurface feature having voids disposed therebetween and having a pillar height of 300 - 1000 nm and a pillar diameter of 100 - 350 nm, A TiO₂ metasurface feature having voids disposed therebetween and having a pillar height of 975 nm and a pillar diameter of 100 - 300 nm, An amorphous Si metasurface feature embedded in benzocyclobutane and having a pillar height of 590 nm and a pillar diameter of 100 - 300 nm, An amorphous Si metasurface feature embedded in SiO₂ and having a pillar height of 600 nm and a pillar diameter of 100 - 275 nm, An amorphous Si metasurface feature embedded in SU8 and having a pillar height of 675 nm and a pillar diameter of 100 - 300 nm, and An amorphous Si metasurface feature in air having a pillar height of 600 nm and a pillar diameter of 100 - 300 nm with an element pitch of 450 nm A metasurface element comprising an array of metasurface features formed from one of the group consisting of (Item 94) (Item 94) The metasurface element according to item 93, wherein the amorphous Si is hydrogenated.

[0104] The description will be more fully understood with reference to the following drawings, which are presented as exemplary embodiments of the invention and should not be construed as an exhaustive listing of the scope of the invention.

Brief Description of the Drawings

[0105]

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Mode for Carrying Out the Invention

[0106] Referring now to the drawings, there are provided metasurface elements, integrated systems integrating such metasurface elements with a light source and / or a detector, and methods of manufacturing and operating such optical arrangements and integrated systems. Many embodiments relate to systems and methods for integrating transmissive metasurface elements with other semiconductor devices or additional metasurface elements, and more particularly to the integration of such metasurfaces with substrates, illumination sources, and sensors. In some embodiments, the metasurface element can be used to shape the output light from an illumination source or collect the light reflected from a scene and form two distinct patterns using polarization. In such embodiments, the shaped emission and collection can be integrated into a single co-designed probe and detection optics.

[0107] In many embodiments, the metasurface element can integrate a multilayer metasurface element that includes a combination of two or more metasurface optical elements. In various such embodiments, the multilayer metasurface element is self-standing (i.e., not directly integrated into the system with a particular illuminator or sensor). In some such embodiments, the optical system can be composed of a single physical component or substrate having a metasurface element disposed on any of its surfaces. In some embodiments, multiple substrates having multiple metasurface elements can be combined to create a more complex system. In such embodiments, the thickness of the substrate can be determined by the requirements of the optical system, manufacturing constraints, and the particular design of the two metasurfaces. In various embodiments, the multilayer metasurface element can be formed by patterning each individual metasurface element on a unique substrate and then fusing the substrates together through appropriate techniques, such as wafer bonding, optical adhesives. However, generally, according to embodiments, any number of metasurface elements can be bonded through any number of steps using CMOS or related processes.

[0108] In many embodiments, the metasurface element can be freestanding or embedded within another material. In various such embodiments, the choice of the embedding material includes an appropriate choice of refractive index and light absorption characteristics. In many such embodiments, the embedding material can provide mechanical stability and protection as well as additional design freedom that enables the metasurface to perform the desired optical functions.

[0109] In various embodiments, the metasurface element can be loaded or fabricated directly onto each facet of an LED, a VCSEL facet, or VCSELs in an array to minimize the device thickness and optimize the metasurface-illuminator / sensor alignment. In some such embodiments, the resulting system can be used to convert natural Lambertian or any arbitrary light dispersion, for example, into a wide range of essentially arbitrary light dispersions including profiles such as a so-called top hat, a so-called bat wing, or any other desired structured light pattern.

[0110] In some embodiments, a spacer layer of a defined thickness (e.g., working distance) is deposited on top of a CMOS image sensor, an LED, a VCSEL, etc. to implement an optical distance suitable for a desired camera design, lighting design, or optimal system performance. In various such embodiments, the spacer layer material can be organic or inorganic and can have a lower refractive index than the dielectric element including the metasurface. In some such embodiments, the thickness of the spacer layer can be varied to provide an appropriate optical spacing for a particular optical system.

[0111] Various embodiments also relate to methods of fabricating metasurface elements. In some such embodiments, the method also relates to the manufacture of metasurface elements on a wafer integrating other devices, such as sensors or illuminators, whereby in some embodiments, costly manufacturing processes, such as, for example, the mechanical assembly of small-sized elements, or the active alignment with sensors of an optical system, are avoided. In some such embodiments, the metasurface element can be integrated with a sensor (or illuminator) in a series of operations in a semiconductor fabrication facility. In many such embodiments, the sequence can include (i) a sensor or illuminator, (ii) an optional microlens array / collimator, an optional filter, an optional spacer layer, an optional metasurface element(s), an optional additional spacer layer, an optional metasurface element(s), an optional anti-reflection (AR) layer, an optional protective layer. In many such embodiments, the sequence of elements can include (i) a sensor or illuminator, (ii) an optional microlens array / collimator, an optional filter, an optional spacer layer, an optional metasurface element(s), an optional additional spacer layer, an optional metasurface element(s), an optional anti-reflection (AR) layer, an optional protective layer.

[0112] Embodiments for manufacturing metasurface elements

[0113] Currently, the fabrication of metasurface devices requires the use of special processes and systems that are not compatible with mass production, limiting the implementation and adoption of such metasurface devices within CMOS devices. An exemplary description of a conventional process for forming a metasurface can be found, for example, in U.S. Patent No. 8,848,273, the disclosure of which is incorporated herein by reference. The ability to fabricate metasurfaces using standard semiconductor processes can enable direct integration with functional elements of metasurface optics, such as light-emitting diodes (LEDs), vertical-cavity surface-emitting lasers (VCSELs), complementary metal-oxide-semiconductor (CMOS) image sensors, microelectromechanical (MEM) devices, etc. Direct integration means the bonding of metasurface devices and sensors / illuminators using unit processes that are the same or similar to those used to fabricate functional CMOS devices.

[0114] Accordingly, many embodiments relate to methods of fabricating metasurface devices and systems, and more particularly, to methods that can be implemented within a conventional semiconductor manufacturing facility. In various embodiments, conventional processes suitable for fabricating metasurface devices can include, among others, photolithography, nanoimprinting, various chemical vapor deposition (CVD), atomic layer deposition (ALD) and physical vapor deposition (PVD) material transfer processes, as well as chemical and plasma etching (and CMS). Referring to the drawings, an exemplary set of fabrication processes tailored for the fabrication of various aspects of embodiments of metasurface devices are presented in the schematic diagrams of FIGS. 1A - 1G.

[0115] The metasurface optical element is composed of a dielectric having a feature size on the order of several tens of nanometers to microns, or generally smaller than the wavelength of light for which the metasurface is used. Referring to FIGS. 1A-1C, in many embodiments, the first step in manufacturing a metasurface device involves patterning and forming an array of metasurface features. In many such embodiments, as shown in FIG. 1A, this metasurface feature forming process is accomplished by depositing a patterning material (14) over a suitable hardmask material (12) having a thickness t (where t is the film thickness and the height of the final metasurface) disposed on a suitable substrate (10). Any suitable deposition technique may be used to form these layers, including, for example, sputtering, chemical vapor deposition (CVD), or atomic layer deposition (ALD).

[0116] Throughout this disclosure, exemplary materials are described with respect to particular embodiments, but it will be understood that any suitable combination of patterning materials, hardmask materials, and substrates may be used for these purposes. For example, in various embodiments, the substrate material is selected to provide suitable structural support and to be transmissive over a desired bandwidth. Exemplary substrate materials that have been successfully implemented using the processes described in the embodiments include, for example, fused silica, sapphire, borosilicate glass, and rare earth oxide glass. Similarly, the hardmask material may be selected from any readily available material suitable for use in a semiconductor fabrication facility. Exemplary hardmask materials include, for example, silicon, silicon nitride of various stoichiometries, silicon dioxide, titanium dioxide, alumina, and the like. For example, in various embodiments, such as when the hardmask material forms an embedding material (as described in more detail below), the hardmask material may be selected to have a low (e.g., 1 to 2.4) refractive index at a particular wavelength of light. Finally, the patterning material according to the embodiments may be formed from any suitable photoresist, such as a photoresist adjusted for a lithography wavelength capable of forming metasurface features of a desired size. Exemplary lithography processes include, for example, ultraviolet and deep ultraviolet (DUV) lithography. In other embodiments, the patterning layer may be a polymer material suitable for use in nanoimprint lithography. Regardless of the particular materials used, the patterning material needs to be able to reproduce the features of the desired pattern on the order of tens of nanometers to microns and to adequately protect the underlying hardmask film within the selected regions in subsequent steps.

[0117] Specifically, as shown in FIG. 1B, once the substrate (10), hard mask (12), and patterning material (14) layers are properly provided, the patterning material is patterned to reproduce an array of features (16) corresponding to either a negative or positive replica of the final intended metasurface feature array structure. The process of creating this feature array pattern can take any form suitable for creating the desired feature size. For example, in embodiments of metasurface elements for use in visible or near-infrared applications, UV lithography (e.g., when the wavelength of operation of the UV lithography step is below 193 nm) can be used. In yet other embodiments, the pattern can be physically imprinted by a master stamp in a nanoimprint lithography process.

[0118] As shown in FIG. 1C, once the desired feature array pattern (16) is properly provided, an anisotropic etching process is used to transfer the desired feature pattern into the hard mask layer (12). An exemplary anisotropic etching process for use according to embodiments is a reactive ion etching process. In a reactive ion etching process, it will be understood that several possible chemistries can be used, including, for example, SF6 gas, Cl2 gas, BCl3 gas, C4F8, or any mixture of these gases. Further, the gas mixture can be static or time-limited in a multiplexed manner where one or more gases are introduced and then, after some set period, followed by one or more gases of a second distinct set. Regardless of the specific anisotropic etching process used, once the pattern is etched into the hard coating layer, the remaining photoresist can be removed using any suitable method (e.g., chemical solvent, chemical etchant, plasma etchant, etc.). It should be noted that in various embodiments, it may be desirable to use the feature array (16) formed within the hard mask material (14) as the final metasurface element. In such embodiments, the process can stop here or, for example, be combined with the deposition of a suitable AR coating or a mechanically protective encapsulation layer as described in FIG. 1G.

[0119] As shown in FIG. 1D, when a particular metasurface material is used in the final metasurface element, the feature pattern (16) (as previously described in FIG. 1C) formed within the etched hard mask (12) can function as a template for the final metasurface structure. In such an embodiment, a separate metasurface material (18) is deposited using a suitable conformal coating method, such as chemical vapor deposition (CVD), atomic layer deposition (ALD), etc., to fill the mask negative and create the metasurface element. As shown in the figure, the metasurface material (18) overfills the space formed by the feature pattern (16) etched into the hard mask (12) to completely fill the depression. In addition to filling the depression (20), this process leaves a deposited layer of metasurface material on top of the remaining hard mask. Again, while a particular metasurface material is described throughout, it will be understood that the metasurface material according to the embodiment can be selected from any readily available dielectric material having the desired refractive index and suitable for use in a semiconductor fabrication facility. Exemplary metasurface materials include, for example, silicon, silicon nitride of various stoichiometries, silicon dioxide, titanium dioxide, alumina, etc.

[0120] Referring to FIG. 1E, once the overfill of the metasurface material (18) is deposited, etching or chemical mechanical planarization is performed according to the embodiment to remove the overfill layer, resulting in a uniform height for the patterned hard mask (12) and the metasurface material (12). In embodiments where an embedded metasurface is desired and a hard coating material suitable to function as the embedding material (as described above) is selected, the process can be stopped and the metasurface material embedded within the resulting hard coating material structure is used as the final metasurface element. This metasurface element can then optionally be coated with a suitable AR coating layer or mechanical protection layer, as described below.

[0121] In various embodiments, as shown in FIG. 1E, the hard mask material (12) is removed, leaving the freestanding metasurface element (20). In such embodiments, the hard mask can be removed using a selective etching chemistry that etches the hard mask material (12) much faster (e.g., 100:1 or 1000:1 or more) than the metasurface material (18). As will be appreciated by those skilled in the art, such a process depends on the particular choice of metasurface material and hard mask material. For example, in embodiments where the hard mask is silicon and the metasurface is TiO2, XeF2 etching chemistry selectively removes silicon while leaving the metasurface material essentially unchanged. Note that in embodiments designed such that the metasurface element is freestanding, i.e., the metasurface element features are separated only by voids (22) and protrude from the edge of the substrate, the process is complete at this step.

[0122] Finally, as described above, in certain embodiments where it is desirable for the metasurface to have an AR coating or a mechanical protection layer, additional steps are required to complete the final metasurface element. Referring to FIG. 1G, in various embodiments, an AR coating or a mechanical protection or planarization layer (24) is also deposited to fill the depressions (22) between the metasurface features (20) and may extend over the surface of the metasurface material layer (18). It will be appreciated that any material having optical properties suitable for a particular optical system design, such as appropriate refractive index and minimal light absorption at a desired wavelength or over a target bandwidth (the planarization layer enables multiple levels of metasurface elements for complex optical systems), can be used in this process. As described above, the metasurface components and the substrate surface are coated with one or more materials or layers of materials in many embodiments to protect the metasurface and provide improved functionality. Referring to FIG. 2A, a schematic diagram of an embedded metasurface is shown. As illustrated, the metasurface features (20) can be made of any material having the desired optical properties as described above and are typically embedded in an embedding medium (24) having a low refractive index. Exemplary embedding materials include, for example, poly(methyl methacrylate), SU8, benzocyclobutene, and / or solid films such as silicon dioxide, aluminum oxide, titanium dioxide, silicon nitride, hafnium oxide, zinc oxide, or spin-on glass. The low-index embedding medium can encapsulate the metasurface features and spread some thickness over the metasurface features. In such embodiments, the low-index medium can function as a protective barrier for the metasurface element (i.e., provide mechanical stability). The embedding material can also provide additional design freedom for a system that allows optimizing certain properties, for example, to improve the overall transmissivity or efficiency of the metasurface, and in some cases, can eliminate the need for a separate AR coating. Here, the embedded metasurface is fabricated on a substrate, but as will be described in detail below, it has been shown that the metasurface can also extend from a sensor / illuminator.The joined elements (metasurface, embedding medium, and substrate) can also be covered with a suitable anti-reflection coating on the surface of the substrate containing the metasurface (26') and / or on the back surface of the substrate (26). In many embodiments, the AR coating can be composed of layers of any combination of silicon dioxide, titanium dioxide, aluminum oxide, silicon nitride, aluminum nitride, or amorphous silicon overlapping alternately, each having a thickness less than the wavelength of light within the operating bandwidth of the metasurface. Accordingly, as described above, the embedding medium itself can potentially be used as an anti-reflection coating.

[0123] Although certain embedded metasurface embodiments have been described above, in various other embodiments, the metasurface can be embedded and planarized as shown in Figure 2B. In such embodiments, the metasurface element can be embedded in a suitable low-index material (as described above), and in an additional step, the embedding medium (24) is then etched or planarized so that its height is equal to that of the metasurface element (20). An optional anti-reflection coating can also be included either on the bare substrate surface (26) or on the patterned metasurface surface (not shown).

[0124] Embodiments for the fabrication of metasurface elements on conventional substrates

[0125] The foregoing has described in detail a manufacturing process capable of forming various self-standing or embedded metasurface elements using conventional CMOS fabrication techniques. However, in practice, it may not be possible to adapt conventional metasurface elements in order to enable the economical production of metasurface elements using equipment that already exists in a semiconductor manufacturing facility. For example, one of the design criteria conventionally used to adjust the optical properties of a metasurface element is the thickness of the substrate. Varying this substrate thickness provides another degree of freedom to the metasurface element designer in obtaining the desired optical properties. However, most of the equipment that already exists in semiconductor manufacturing facilities has constraints that result in specific mechanical requirements regarding the substrates on which metasurface elements are fabricated. For standard substrate diameters in semiconductor manufacturing facilities, e.g., 200 mm and 300 mm, the substrate thickness is limited to 725 microns and 775 microns, respectively. These fixed substrate thicknesses, as a result, impose specific requirements on the optical functionality, and thus the design, of the metasurface formed on such a substrate or a system of multiple metasurfaces formed on such a substrate (in high volume production, there may be, for example, 5,000 metasurfaces, or more, formed on a single die).

[0126] Accordingly, many embodiments relate to a process for fabricating a metasurface element or system to match the thickness of a particular substrate on which the metasurface or metasurface system is fabricated. For example, in various embodiments, the phase shift that needs to be imparted by a metasurface element to impart a particular function to an entire optical component(s) will be specific to the thickness of the substrate on which the element is formed. Accordingly, in some embodiments, the procedure for designing and fabricating a metasurface element includes (1) considering the device specifications of the metasurface element, (2) considering the thickness and optical properties (refraction and absorption rate) of the substrate on which the metasurface is formed, (3) optimizing the phase profile of the metasurface to achieve the desired specifications for the substrate's properties, and (4) determining the thickness and in-plane dimensions of the metasurface element necessary to reproduce the phase profile.

[0127] Referring to FIG. 3, an exemplary process is provided in accordance with the manufacture of a metasurface using a standard substrate thickness. As shown in the figure, following the deposition and lithographic patterning and etching of the metasurface material (as described above in FIGS. 1A - 1G), if the metasurface layer is designed for a standard substrate thickness, an additional protective layer or AR coating can be placed on the metasurface layer before being sent for further back - end processing. In many such embodiments, the back - end processing can include singulating thousands of metasurfaces formed across the substrate using a dicing process. Further, in a desired embodiment for manufacturing a metasurface having a final substrate thickness different from the standard thickness described above, additional steps can be performed to change the thickness of the underlying substrate. In such embodiments, the metasurface is initially formed with respect to a standard substrate diameter (200 or 300 mm) that again matches industry standards and a standard thickness in the semiconductor process (725 or 775 microns respectively). After initially defining the metasurface on a substrate of standard thickness, subsequent back - end processing is performed to change the thickness of the substrate. Suitable methods for changing the thickness of the substrate in accordance with embodiments include, for example, grinding or a combination of grinding and chemical treatment to gradually remove the substrate material. In such embodiments, the final substrate thickness on which the metasurface is formed can be any value less than the starting standard thickness. Alternatively, if a thicker substrate is required, two independent wafers, each containing any number of metasurfaces (1,000 - 10,000 individual metasurfaces), can be joined in accordance with an embodiment to achieve the desired thickness in a wafer bonding process, such that the final monolithic unit has a set of metasurfaces on both sides and an overall thickness as required by the final design. A process in accordance with such embodiments can be performed on two substrates of standard thickness if the required final thickness is twice the standard thickness, or on two substrates that have been thinned and joined such that the final thickness of the unit has any desired thickness.In such an embodiment, the "backend processing" may include additional wafer bonding steps that can align each of the individual substrates with each other before they are bonded.

[0128] Embodiments for manufacturing metasurface elements with non-ideal characteristics

[0129] In a conventional process for designing a metasurface, the shape conformity of what is manufactured from the designed metasurface is often assumed to be either a one-to-one correspondence or within some error range. This approach results in a metasurface array that often consists of a single set of shapes where one characteristic of the set of shapes varies, for example, a circle with a varying diameter across the metasurface. However, manufacturing techniques used for potential mass production of metasurfaces, such as UV lithography as described above, generally cannot perform a faithful reproduction of a given geometry. Therefore, many embodiments relate to metasurface elements and metasurface manufacturing processes where the function of the metasurface is reproduced using non-ideal and non-uniform shapes.

[0130] For example, FIG. 4A provides a schematic cross-sectional view of an exemplary cross-section of a metasurface where a non-uniform set of shapes is distributed across the metasurface. In this particular embodiment, square pillars are desired. However, after manufacturing, what is actually formed within a given metasurface is a square with a varying side length (e.g., s1), a square with rounded corners with a varying radius r e and an array of circles with varying radii r1 or r2. Specifically, larger features are here designed to be squares or squares with rounded corners, but as the side length of the square shrinks somewhat below the minimum side length, the square becomes a circle. In the process according to the embodiment, the manufacturing limits are simulated for each desired metasurface feature shape, and these non-ideal or non-uniform feature elements are then used to determine the final metasurface element array structure.

[0131] For example, FIGS. 4B and 4C provide diagrams illustrating printing from a metasurface element mask reticle and variations in the designed pattern. As shown in the figures, in embodiments for designed square features with periods of sides 200 nm and 450 nm, the printed manufacturing technique actually replicates circles with a diameter of 200 nm (FIG. 4B). In contrast, for square features with a spacing between sides of 296 nm and 450 nm, the manufactured features are squares with rounded corners (FIG. 4C). As a result, many embodiments of metasurface elements in which square metasurface features are designed may be replaced with rounded squares less than about 300 nm and circles less than about 200 nm to enable the use of industry-standard CMOS reproduction techniques.

[0132] Embodiments for manufacturing multiple metasurface elements

[0133] As described above, various embodiments relate to a method for wafer bonding two substrates to integrally combine metasurface elements. Such embodiments can be modified, for example, to enable the facile manufacture of multiple metasurface elements (e.g., metasurface elements including two or three separate metasurface feature arrays), such as doublets and triplets. Specifically, there are many wafer bonding processes, each of which imposes a specific thermal budget on the substrates being bonded. Since many embodiments of metasurface elements use amorphous Si as the metasurface material, overheating of the substrate can result in crystallization of the Si. Accordingly, embodiments are presented that enable wafer bonding of two or more metasurface elements at low temperature using a low-temperature process, for example, using a UV-curable polymer (such as benzocyclobutane (BCB) or the like), or plasma-activated SiO2, to enable the formation of metasurface doublets and triplets.

[0134] Referring to FIG. 5, a schematic diagram for forming a metasurface doublet according to an embodiment is shown. As illustrated, in many such embodiments, a plurality of unique metasurface elements (30&32) are fabricated on two separate substrates (34&36). The metasurface elements are then made into a bonding system by fusing the bottom surfaces of each unique substrate (e.g., the portion of the surface of the substrate without the metasurface elements). As described above, the substrates can be fused by wafer bonding techniques, optical epoxies, or any suitable method for joining two unique elements into a single element within the allowable thermal budget of the metasurface material being used. The bonding material (38) in many embodiments can be an adhesive such as benzocyclobutene, cured polymer SU8, or a silicon dioxide film that facilitates glass bonding. In cases where the thermal budget of the metasurface material is low (less than 600 °C), the silicon dioxide bond can be a low-temperature plasma-activated SiO2 bond. Additionally, although not shown, the metasurface can be encapsulated as described in the embodiments illustrated in FIGS. 2A and 2B. In addition, as described with reference to FIG. 3, the thicknesses of the two substrates, which ultimately make up the total thickness of the space between the metasurfaces, can be further varied to optimize certain characteristics of the bonding system.

[0135] The present disclosure has heretofore detailed embodiments incorporating only two metasurface elements, but the process can be generalized to any number of metasurface elements. For example, in certain applications, it may be required to bond three or more metasurfaces into a monolithic unit. In such cases, two substrates containing separate metasurface elements can form the initially unbonded unit. An illustration of an exemplary embodiment of such a process is provided in FIG. 6. As shown in the figure, in many such embodiments, at least one of the metasurface substrates (40) has only one side patterned with metasurface elements (42), while the opposite side of the substrate can be completely unpatterned or can also include a bandpass filter (44) for a particular wavelength of interest. In such embodiments, the filter can be formed from one or more suitable materials, for example, alternating layers of low and high refractive index materials such as silicon dioxide, titanium dioxide, amorphous silicon, silicon nitride, and aluminum oxide. At least a second metasurface substrate (46) has two unique metasurface elements (48&50) on each side of the substrate (this second metasurface substrate may itself have been formed through its own intermediate bonding step as described previously in connection with FIG. 5). The metasurface substrates (40&46) are then made into a bonding system by fusing the bottom surfaces of each respective substrate (e.g., the portion of the surface of the first substrate (40) without metasurface elements with the portion of the surface of the second substrate (46) containing one of the two metasurface elements (48&50)). As previously described, the substrates can be fused by wafer bonding techniques, optical epoxy, or any suitable method for bonding two unique elements into a single element within the allowable thermal budget of the metasurface materials used. The bonding material in many embodiments can be an adhesive such as benzocyclobutene, cured polymer SU8, or a silicon dioxide film that facilitates glass bonding. In cases where the thermal budget of the metasurface material is low (less than 600 °C), the silicon dioxide bond can be a low-temperature plasma-activated SiO2 bond. This bonding material is placed on or between the surfaces of the two substrates being bonded.In one embodiment, various metasurface elements can optionally be encapsulated as described above (52&54). However, in many embodiments to facilitate the bonding process, metasurface elements (48) that are proximal to either the bare substrate surface or the bandpass filter (44) within at least the bonded triplet device are embedded within a polymer and / or solid bonding agent (56).

[0136] In the foregoing examples of bonding metasurface elements, each metasurface element is separated by a solid substrate. However, in some embodiments, each metasurface element can instead be separated by a void. Referring to FIG. 7, a schematic diagram of a metasurface doublet including a void is shown. As shown in the figure, in many such embodiments, two or more metasurface elements (60&62) are formed on respective substrates (64&66) using an appropriate method such as the method described above in connection with FIG. 5. The respective metasurface elements are then bonded to a third substrate or spacer substrate (68) including one or more etched openings (70) to create a monolithic unit, where the space within the opening between the metasurfaces is not filled (i.e., a void is formed between the metasurface elements (60&62) therefor). The space between the metasurfaces provides additional design tools for system-level optimization. For example, in many embodiments, various different designs can be implemented by adjusting the thickness of the spacer wafer. Additionally, in various embodiments, as also shown in FIG. 7, it is possible to add an additional spacer substrate (72) to incorporate other system elements such as illuminators and / or sensors (74).

[0137] In embodiments incorporating such a spacer substrate, any suitable substrate material can be used. For example, in many embodiments, the spacer substrate can be any low-index material such as, for example, polymers, SiO2, glass, etc. Additionally, in other embodiments, the spacer material can be coated with black chrome. The metasurface elements can be formed from any material, which is optimized for a particular bandwidth, such as, for example, silicon, TiO2, alumina, metals, etc. The metasurface elements can be fabricated using such methods as described in FIGS. 1A-1G or using semiconductor manufacturing processes in general.

[0138] In the foregoing embodiments, the process for joining the metasurfaces of 2 and 3 has been described, however, such embodiments can be extended beyond simply 2 or 3 metasurfaces. For example, by repeating the steps described above in connection with FIGS. 5-7, embodiments enable stacking of any number of metasurface elements. Referring to FIG. 8A, in various embodiments, a set of metasurfaces (80, 82, 84, etc.) and spacer layers (86, 88, etc.) can be directly integrated with an illuminator or sensor. In such embodiments, an optional spacer layer (90) is first formed on the sensor / illuminator (92) through a suitable deposition process as described above in connection with FIGS. 1A-1G. Following the spacer layer (90), any number of metasurface elements (80 - metasurface n+1) can be fabricated as needed to perform the desired function. Each subsequent metasurface can also be separated by a spacer layer (86 - spacer n+1), and the thickness of each intervening layer can be varied as required by the optical design. As described above, the spacer layer can be any low-index material, such as, for example, polymers, SiO2, glass, in such embodiments. Similarly, as described above, the metasurface elements can be of any material in such embodiments, which is optimized for a particular bandwidth, such as, for example, silicon, TiO2, alumina, metals, etc. The metasurface elements can be fabricated using such methods as described in FIGS. 1A-1G or using other suitable semiconductor manufacturing processes in general.

[0139] While the foregoing assumes integration with a sensor or illuminator (92), the set of metasurface elements and spacer layers can also be fabricated iteratively on a substrate (90), as shown in FIG. 8B. As shown in the figure, in such an embodiment, the process is as described in connection with FIG. 8A, except that instead of integrating the metasurface / spacer stack on the sensor / illuminator (92), the stack is fabricated on a stand-alone substrate (90). The substrate and stack bonded in accordance with such an embodiment can then be incorporated into an optical system or used as a stand-alone optical component.

[0140] Embodiments of Multilayer Metasurface Elements and Their Manufacture

[0141] In the embodiments detailed above, each metasurface element is designed to perform a unique optical function in a larger optical system, and the metasurface elements are typically separated by macroscopic distances (distances of 10 or more wavelengths). However, in various embodiments, multiple two-layer patterned materials can be provided at microscopic distances from each other (e.g., at distances smaller than or of the same order as the wavelength of light), such that the layers together form a single metasurface element and perform a single optical function. This can be particularly advantageous when optical functions requiring very complex metasurface features are desired. Such complex features can exceed the capabilities of standard CMOS manufacturing techniques for fabrication. In such cases, a combination of simple features arranged at microscopic distances in accordance with an embodiment can be used to reproduce the optical function of a complex feature shape. Referring to FIG. 9, a schematic view of an embodiment of a metasurface element including two layers of patterned material separated by a distance t offset is provided. Only a schematic view of a two-layer system is shown, but it will be understood that any number of such layers can be provided as long as the distance t offset is small enough to allow a combination of the optical functions of the multiple layers. These feature layers can be formed and bonded using any suitable combination of the manufacturing steps described above in connection with FIGS. 1-8.

[0142] Embodiments for integrating a metasurface element with a VCSEL

[0143] The techniques and processes for fabricating metasurface elements according to the embodiments also enable their direct integration with illumination sources. Of particular interest is the combination of metasurface elements with VCSELs and VCSEL arrays. In general, transmissive metasurface elements can imprint an arbitrary phase profile onto an electromagnetic wave to generate an arbitrary radiation pattern in the far field. The manufacturing techniques for metasurface elements according to the embodiments enable direct integration with VCSELs, solid-state lasers, quantum cascade lasers, LEDs, superluminescent LEDs, or any solid-state light source.

[0144] A VCSEL can be conceptualized as a single (or two, three) mode laser that generates a nearly parallel beam of laser light at a single wavelength. In many cases, to generate sufficient output or spatial spread, the device includes a two-dimensional array of VCSELs rather than a single VCSEL. This light has a distribution (or illumination) in real space and angular space. The metasurface, when properly designed and integrated with the VCSEL array, has the ability to transform both the real space and angular space distributions of either the VCSEL or the VCSEL array. Specifically, combining a metasurface element with a VCSEL enables the metasurface element to imprint an arbitrary radiation pattern onto the source (e.g., a bat wing, a top hat, a super-Gaussian, or other patterns known in the art).

[0145] FIG. 10A presents a flow diagram of a process for fabricating a metasurface to create any desired far-field intensity from a VCSEL array, according to an embodiment. To obtain illumination in real space, the VCSELs are assumed to operate within the far-field region, according to an embodiment. The characteristic far-field of the VCSEL (VCSEL-FF) is propagated from experimental data to the surface under illumination, which in this case is the metasurface element as defined above. In the case of a VCSEL array, the outputs from many VCSELs through the (VCSEL-FF) are summed at the surface to generate illumination under the assumption of non-interference. This surface illumination then gives the intensity distribution at the metasurface element (I-MS). Every point on this illuminated surface also has a distribution of the angles of the incident light thereon, obtained from the VCSEL far-field angular distribution. In a simplified case, it is possible to consider, according to an embodiment, the case where all illuminated points have this same VCSEL far-field angular distribution, although each point has a slightly different angular distribution.

[0146] To generate a metasurface element that takes into account the angular distribution in the metasurface element within the design, embodiments of this process construct a pseudo far-field (PSEUDO-FF) with characteristics from the target far-field distribution (TARGET_FF), and its convolution is ((PSEUDO-FF)*(VCSEL-FF))(x,y)=(TARGET-FF)(x,y) (Equation 1) That is, according to an embodiment, the pseudo far-field convolved with the VCSEL far-field reproduces the target far-field. In such an embodiment, the pseudo far-field is calculated by fitting a curve to the target function. Then the (PSEUDO-FF) is used as the target (or objective function) for the remainder of this process.

[0147] In various embodiments, the process starts by initializing the metasurface lattice by discretizing it and setting the phase to some initial state. In many embodiments, a cost function is determined. In various embodiments, this is selected to be the mean squared error of the far-field projection of the metasurface under VCSEL illumination with respect to (PSEUDO-FF). In some embodiments, other goals, such as the smoothness of the result in the calculated far-field, can also be optionally set. For each goal, a corresponding gradient function is also derived. The calculated results of this gradient function and the cost function are then, in embodiments, used as inputs to an optimization algorithm according to the embodiments, as summarized in FIG. 10A. The optimization algorithm updates the result of the pixel phase according to the embodiments and continues until the objective function satisfies some criterion (e.g., convergence). When the cost function converges, the required metasurface phase profile is output, and the metasurface element design is selected according to the wavelength and the desired material (e.g., as described in detail below) so that a physical design for the metasurface element can be created.

[0148] Exemplary data plots show the output of the process with respect to phase (10B) and intensity (10C) after employing the algorithm described above for an exemplary case according to embodiments. As shown in the figure, in such embodiments, the phase is encoded by the metasurface element and the intensity profile on the right is generated after the laser source passes through the metasurface element and projected into the far field. Accordingly, using such a process, it is possible to obtain predicted performance data for a proposed metasurface element under desired operating conditions and illustrate ways to optimize its performance by changing aspects of the metasurface element design, such as the size, height, and spacing of the element.

[0149] Embodiments for integrating a metasurface element with an illumination array

[0150] The foregoing process has focused on integrating the metasurface element with a single illumination source, as shown, for example, in FIGS. 7 and 8A. However, the metasurface element can also be integrated with a set of pixelated and distributed illumination sources. As illustrated in FIG. 11, various embodiments include a set of illumination sources, p1, p2, ··· p n (although shown in 1D, it will be understood that the system can be extended to a 2D array and, in general, the array need not be periodically spaced). Each illuminator can be identical, but in many embodiments, the characteristics of each illuminator can generally be unique. For example, each illuminator can have a different wavelength, bandwidth, or even output a uniquely driven optical waveform. For certain applications, the array in FIG. 11 can be an array of VCSELs. In other applications, there can be three colors (e.g., red, green, and blue) that are periodically repeated thereafter within the array. Since each illuminator including the array can have unique characteristics, it can also be convenient to have an array of metasurface elements, each with uniquely designed characteristics. In such embodiments, the metasurface array (100) can be offset from the illuminator array (102) by a spacer (104) (similar to FIG. 7 or FIG. 8B). As described above, the thickness of the spacer layer (104) is determined by a specific design, but in many embodiments, the thickness is configured to allow the light from the illumination source to diverge sufficiently before contacting the metasurface array (100). Again, the function of each metasurface element within the array can generally be unique, but in some embodiments, each metasurface element can provide collimation of the underlying illuminator pixel or can function to further mix each underlying illuminator pixel.

[0151] In addition to the first metasurface array (100), various embodiments may incorporate a second metasurface element (106) to further shape the emitted light from the luminaire array (102). In various embodiments, the second metasurface element (106) is also offset by a second spacer layer (108). This second spacer layer (108) is shown as a void spacer in FIG. 11, but it will be understood that this spacer can also be a solid material as in the other embodiments described above. In many embodiments, the first metasurface array (100) is configured to introduce additional angular divergence into the luminaire array (102), while the second metasurface element (106) imprints a specific far-field radiation pattern onto the bright field. In other embodiments, the second metasurface element (106) can also be formed from an array of metasurface elements, each with its own functionality. In all such embodiments, the metasurface elements, and in particular, the second metasurface element within the system, can be designed using the embodiment of the algorithm described in FIG. 10A. In this particular case, the system is described as an array of pixelated luminaires (102) shaped by the metasurface array / element to illuminate a scene (110), but the system can also be considered in reverse. For example, the pixelated illumination source could instead be the pixels of a CMOS image sensor, and instead of light projected onto the scene, the system could be configured to collect light from the scene (10) and focus that light onto the pixels.

[0152] In all embodiments where the illumination source is a VCSEL, it is understood that the present disclosure is also applicable to an array of VCSELs (VCSEL array). In such a VCSEL array, many individual aperture VCSELs with designable characteristics are bonded onto a single chip. Such a VCSEL array is used to increase the total output of the illumination source. The array can be composed of a one-dimensional row of individual VCSELs or a 2D lattice of individual VCSELs, and in each case, the specific characteristics of the VCSELs (e.g., output, wavelength, aperture diameter, beam divergence, etc.) and the arrangement of the individual VCSELs (e.g., center-to-center distance, periodic or aperiodic spacing, etc.) can all be freely selected.

[0153] In the context of metasurface element integration, embodiments of metasurface elements with inherently designed characteristics (but not necessarily) can be patterned on each individual VCSEL in the array using any of the techniques outlined herein. For example, the metasurface can be fabricated directly on the facets of each individual VCSEL in the array, or a suitable dielectric spacer can be deposited on the VCSEL, followed by integration of the metasurface on the deposited dielectric layer and the VCSEL. In such embodiments, the metasurface can provide a specific radiation pattern for each VCSEL, and the overall system (VCSEL characteristics, geometric parameters, and metasurface-corresponding radiation pattern) can be iteratively optimized for a specific set of performance parameters.

[0154] In various other embodiments, a dielectric material having a refractive index lower than that of the constituent VCSEL material can be deposited and planarized such that a single metasurface can be patterned on the dielectric material. This is in contrast to embodiments where each VCSEL in the array has an individual metasurface patterned on its facet. Again, in such embodiments, the integrated system can be optimized to achieve the desired performance. Finally, in all of the foregoing embodiments, the integration of the metasurface with the VCSEL array can be achieved using wafer-level optical processes. In such embodiments, the spacer layer can be air rather than a solid dielectric, similar to the device shown in FIG. 7.

[0155] Embodiments for integrating metasurface elements for 3D applications

[0156] In certain 3D structured light applications, a pseudo-random binary array (PSBA) is projected onto a scene. A typical PSBA is constructed, for example, by discretizing a 2D space within a square lattice. Each lattice point in the x-y plane can be characterized by a unique index (i,j), where i and j are integers. At each point (i,j), a pseudo-random algorithm is used to determine whether the lattice point has a dot (representing a binary 1) or does not have a dot (representing a binary 0).

[0157] Typically, a diffractive optical element (DOE) is used to convert incident laser light, for example, from a VCSEL or an array of VCSELs, into a single dot pattern. Such a conversion method depends only on two intensity values (dot or not dot) in the projected area. However, in general, it is desirable to have multiple patterns given to a single scene and to have a separable information channel for each of the multiple patterns (i.e., to have two patterns projected onto a scene from a single element and to have a method for uniquely identifying each pattern in the sensor plane). In some methods of 3D imaging, multiple patterns are projected onto the scene at different time slices (temporal variation). These methods use either multiple distinct illumination patterns or some active element, such as a spatial light modulator, that can be electrostatically adjusted to change the projected pattern at different times. However, these methods do not permit single-shot acquisition, and the complexity, and thus the cost of the system, tends to increase substantially beyond that of an integrated laser / DOE. Accordingly, many embodiments relate to metasurface elements configured to provide single-shot acquisition for 3D structured light applications.

[0158] Referring to FIGS. 12A - 12C, an exemplary embodiment of a metasurface element (120) is provided that consists of a plurality of metasurface features (122) having an asymmetric cross - section (e.g., rectangular or elliptical), a fixed height, and a rotation axis, and is capable of imprinting two unique dot patterns with two orthogonal polarizations onto an illumination source (124). This exemplary embodiment is described with respect to a laser with fixed polarization, but the embodiment can also be configured to operate with an unpolarized source (e.g., a light - emitting diode (LED)), in which case the function of the metasurface element would be to split the unpolarized light into two separate polarizations (as schematically shown in FIG. 12B) and imprint an arbitrary desired pattern onto the projected light. Whatever the illumination source, in various other embodiments, the metasurface element can be integrated with an illumination source (e.g., an LED, a VCSEL, a VCSEL array, etc.) according to the embodiments described in this disclosure. For example, referring to FIG. 12A, the metasurface element (120) is fabricated on a substrate (126) of a desired thickness and then joined to a spacer layer that is later joined to the illumination source (124), joined directly to the illumination source, or the substrate on which the metasurface element is formed is later diced into individual units and can be joined to the laser source through back - end packaging. For various embodiments of a 3D imaging system, the illumination source can be near - infrared (NIR) (e.g., a wavelength of 850 or 940 nm).

[0159] Regardless of the specific configuration and manufacturing of the metasurface element used, in such embodiments, the metasurface element operates by shaping not only the intensity but also the polarization of the light emitted from the illumination source. Specifically, in addition to intensity variations, light also has a vector quantity known as polarization. Given a polarized illumination source, it is possible to decompose the illumination polarization into two orthogonal polarizations or the basis of the channels. Due to the orthogonality of these polarization bases, any pattern imprinted on these different polarization channels can also be independently detected through a suitable detector configured to separate these polarization channels.

[0160] As a specific example, consider the following case. Horizontal polarization

Number

Number

Number

Number

[0161] As described above, embodiments operate as a result of the orthogonality of polarization channels on which each pattern is imprinted. Due to this orthogonality, reflected light from a given scene can be separated by appropriate detectors and, as shown in FIG. 12B, multiple images of the same scene, one with polarization 1 corresponding to pattern 1 and one with polarization 2 corresponding to pattern 2, can be created. The end result is that embodiments of such a system provide two nominally independent measurements of the distorted pattern reflected from a scene without the need for time-division multiplexing. Accordingly, embodiments of such a system can be used to provide single-shot, multiple measurements in a 3D imaging system, thus reducing ambiguity and improving accuracy.

[0162] Typical pattern projection systems used in mobile devices, for example, are limited in the total number of points that can be projected onto a scene. This limitation results from a combination of the number of constituent VCSELs within a VCSEL array (which cannot be changed by the operation of the optical system that generates the pattern) and the ability of the optical system that generates the structured light pattern to create multiple replicas of each VCSEL included in the VCSEL array. In practical embodiments, this limits the number of projection points within a pattern to a specific number N (typically on the order of 30,000). According to embodiments of the polarization-dependent metasurface system described above, since a single metasurface element has the ability to create multiple fully distinct patterns for each orthogonal polarization, even within the aforementioned limitation, the total number of dots within a given pattern can be doubled (e.g., 2N) and, in a typical system, can reach a number of 60,000 points in a single projection pattern. This doubling can be understood by examining the nature of the pattern. Conceptually, a typical projection pattern has a set of lattice points separated by some period p. A short distance away from the projector, the pattern spreads into a field of view given by the vertical and horizontal distances, H and Y. For a conventional projector, a maximum of 30,000 lattice points fill its field of view and, for that purpose, the product

Number

[0163] Finally, since two distinct patterns can be generated from the system according to the embodiment, such a system can also be optimized for both short-range (<1 m) and long-range (>1 m) 3D imaging. For example, one pattern can be configured to distinguish an object at a short distance from the device, while a different pattern can be configured to distinguish a pattern that is far away from the device. In such an embodiment, it would be possible to use a single device to create, for example, in a single shot, pattern 1 with polarization 1 for short-range measurements and pattern 2 with polarization 2 for long-range measurements.

[0164] Embodiment for integrating a metasurface element into an imaging system

[0165] In some embodiments, integrating multiple metasurface elements (e.g., two or more) using the methods as described in FIGS. 7 and 8 enables the combined system to achieve the functionality required for practical CMOS camera imaging. Specifically, a CMOS camera (used in a mobile phone, computer, tablet, etc. to collect an image of a visible light scene or with infrared for biometric authentication, etc.) requires that the imaging system have an increased field of view (FOV), independent control of the chief ray angle (CRA) as a function of the field of view height in the CMOS image sensor, and minimal optical distortion of the scene being imaged. These terms are understood to have their ordinary meaning to those skilled in the art. With respect to a conventional imaging system composed of refractive lenses, to perform this function, it is necessary to bond 5 or 6 individual lenses. Moreover, implementing one metasurface element within such an imaging system does not provide sufficient degrees of freedom to properly control these parameters (CRA, FOV, and minimization of distortion). However, by bonding multiple metasurfaces, each with its own unique and independent phase profile, an imaging system with a wide FOV, controllable distortion, and controllable CRA can be realized according to the embodiments.

[0166] Referring to FIG. 13, a ray tracing diagram according to an exemplary embodiment of a system having two metasurface elements (130&132) bonded onto a single substrate (134) in accordance with an embodiment is provided. In various such embodiments, the metasurface elements on both sides of the substrate are formed to have the same height (although not described in detail herein, these metasurface elements are fabricated using methods as described in any of the foregoing figures and can be bonded, for example, using a process such as the process described in FIG. 5. In many such embodiments, the metasurface elements can be formed from a film deposited simultaneously on both sides of the substrate using a suitable conformal deposition process, such as low-pressure chemical vapor deposition or atomic layer deposition). In this exemplary embodiment, the two metasurface elements are configured to be bonded to form a good image over a wide FOV (±44 degrees in this example, although it will be understood that this is not a limiting case). As shown in the figure, embodiments of such a two-metasurface system have surprisingly been found to generate naturally focused rays in the plane of the filter and in the telecentric (i.e., having a 0-degree CRA) image plane. Briefly, in a conventional refractive design, a complex, multi-element system is required to achieve such a telecentric design, whereas according to the embodiment, only two metasurface elements are required to achieve similar telecentricity. This telecentricity results in improved optical characteristics. Specifically, the low height (e.g., zero or near-zero degrees of CRA) enables narrowing the bandwidth of the optical filter (136) for narrowband applications. In a conventional refractive design, especially for small mobile applications, the CRA is typically on the order of 15 degrees to 30 degrees. These larger CRAs consequently require a significant increase in the filter bandwidth and allow more ambient light to enter the detector. In narrowband applications (e.g., near-infrared VCSEL arrays), such ambient light can be a persistent noise source. Thus, embodiments of the bonded metasurface / filter system as shown in FIG. 13 enable better ambient light performance.

[0167] Additional features of embodiments of such telecentric designs are that the metasurface system provides more uniform illumination (referred to by those skilled in the art as "relative illumination") in the image sensor. Embodiments of the metasurface system also provide additional design changes with respect to conventional refractive lens systems. In a typical complementary metal-oxide-semiconductor (CMOS) image sensor (CIS), it is necessary to associate microlenses with each pixel. Since there are large variations in the chief ray angle (CRA) across a given sensor plane that are inherent to refractive optical systems, the microlens array on the CIS also requires complex CRA specifications. However, in embodiments of the metasurface system as described herein, the CRA of the microlens array is configured to be a constant 0 degrees across the CIS, which may enable a higher level of simplicity in the design and manufacture of the microlens array. Alternatively, in some embodiments, the microlens array may be completely removed from the CIS, saving process steps in CIS manufacturing.

[0168] ​Embodiments of the metasurface system for use with a CMOS sensor have heretofore been shown using two metasurface elements on opposite sides of a single substrate, but in various other embodiments, the two metasurface elements can be disposed on separate substrates. An exemplary embodiment of such a system is illustrated in FIG. 14. As shown in the figure, in many such embodiments, the metasurface elements are disposed on two separate substrates (138 & 140) with a gap (142) disposed between the two elements. One advantage of such embodiments incorporating a gap is that light rays can bend more in air than in a glass substrate over a short distance d, allowing for further expansion of the illumination zone with a shorter separation between the metasurface elements, and thus enabling a reduction in the overall form factor of the metasurface optics. As shown in FIG. 14, in various embodiments, the metasurface elements are disposed over the gap (142) facing the surfaces of the substrates (138 & 140). Such an embodiment allows for protecting the metasurface elements from environmental contamination. Additionally, such embodiments allow for leaving the outer surface of the imager-side substrate (140) unpatterned and enable integrating an optical filter (144) directly onto the substrate. In the embodiment shown in FIG. 14, the metasurface elements are disposed to face inward with respect to the gap between them, but it will be understood that they can be disposed on any surface of the two substrates. The fabrication of the metasurface system shown in FIG. 15 can follow the aforementioned processes, such as the process associated with FIG. 7 for example.

[0169] The foregoing has described a metasurface system configured to provide telecentric optical characteristics. However, in some cases (e.g., when distortion correction is required), it is necessary to introduce a non-zero CRA. Accordingly, embodiments also relate to a metasurface system including at least three metasurfaces that can simultaneously control the FOV, distortion, and CRA. A ray-tracing diagram of an exemplary embodiment of a metasurface system including three metasurface elements having unique phase profiles is shown in FIG. 15. Introducing additional metasurface element(s) or elements, each enabling the realization of a distinct arbitrary phase profile, provides an additional degree of freedom in controlling the ray path compared to a typical system composed of a significant number of refractive elements. For example, to double the optical functionality of a system consisting of three metasurfaces according to an embodiment, six to seven refractive optical elements may be required in a conventional system. Thus, the comparative metasurface system can reduce the overall thickness of such an imaging system by at least 50% while achieving equivalent or even improved performance.

[0170] As shown in FIG. 15, looking at the metasurface system itself, such an imaging system can include three or more metasurface elements (150, 152 & 154) disposed on two or more substrates (156 & 158). As described above, these metasurface elements can be composed of any suitable dielectric material, particularly a dielectric material having minimal absorption at the wavelength of interest. As shown in the figure, in various embodiments, the first two metasurface elements (150 & 152) can impart telecentric optics to the incident light, while the third metasurface (154) (e.g., the one closest to the filter (156)) and the imager impart further divergence or bending to the light and thus can give a non-zero CRA to the light impinging on the imager. Although a particular arrangement of metasurface elements and substrates is shown in the system illustrated in FIG. 15, such a schematic is intended to serve as an example and does not limit the present disclosure to such a system response. Regardless of the particular arrangement of the elements, the manufacture of such metasurface elements can follow the processes described above, such as the process illustrated and described in connection with FIG. 6, for example.

[0171] Using such a three-metasurface element system according to an embodiment, it is possible to control the CRA and thus minimize the grating distortion in a CMOS image sensor. For example, FIG. 16 provides a data plot showing the control of the resulting CRA as a function of the field height in a CMOS image sensor for an imaging system based on the embodiment shown in FIG. 15. This is an exemplary case, and the control of the CRA as a function of the field height can take other functional forms rather than the linear case shown below. Similarly, FIG. 17 provides a grating distortion plot for an imaging system based on the embodiment shown in FIG. 15. As shown in the figure, embodiments of such an imaging system can minimize the grating distortion to less than 5% across the entire FOV of the imaging system.

[0172] Embodiments for Incorporating Metasurface Elements into an Imaging / Detection System

[0173] Given the advantages described for use on both the detection optical system and the projection optical system of a metasurface element according to an embodiment, various embodiments relate to a metasurface system configured for use in a combined illumination-detection module. Referring to FIG. 18, a schematic diagram of an integrated illuminator and sensor system according to an embodiment is provided. As shown in the figure, in such an embodiment, an illuminator having a plurality of spacers (162&162') and metasurface elements (164&164'), either alone or together with refractive elements configured to provide a particular radiation pattern, is used to illuminate some object or scene (166). A sensor (168) (e.g., a CMOS image sensor) with a corresponding metasurface system is used to detect the radiation or form an image of the scene. In such an embodiment, the entire system - the metasurface elements (162&162'), the sensor (168), the illuminator (160) - can be configured to operate over some particular bandwidth or at a particular wavelength of interest and can be joined on a single platform (170). The illuminator and sensor metasurface elements (162&162') can be configured to affect any polarization of the electric field. Embodiments of such joined systems can be used on computers, mobile phones, television monitors, wall-mounted units, credit cards, tablets, mirrors, etc.

[0174] As previously described in connection with FIGS. 12A - 12C, the metasurface enables its unique functionality to be imprinted on two orthogonal polarizations. Thus, various embodiments of the metasurface illuminator - detection system can also be co - designed to consider polarization as an additional optimization variable. Referring to FIG. 19, a schematic diagram of an integrated illumination system that also acts on the polarization of the radiation field is provided. As shown in the figure, in one such exemplary embodiment, an illuminator (172) having one or more metasurface elements (174&174´) along with appropriate spacers (176&176´) and optionally refractive elements is used to irradiate a scene or object (178). The metasurface elements in such an embodiment are designed such that for any two orthogonal polarizations of light, two distinct and independent radiation patterns can be generated. A sensor (180) with a corresponding set of metasurface elements is used to collect the light reflected from the scene. As shown in the figure, the illuminator and sensor metasurface elements are configured to cooperate such that the two orthogonal polarizations of light used to generate the radiation pattern form two distinct images on the sensor. The system - metasurfaces (174&174´), sensor (180), illuminator (172) - can be optimized to operate over some specific bandwidth or at a specific wavelength of interest according to an embodiment and can be bonded on a single platform (182). It will be understood that the illuminator and sensor metasurface elements according to an embodiment can be configured to affect any polarization of the electric field. The bonded system according to an embodiment can be used on a computer, mobile phone, television monitor, wall - mounted unit, credit card, tablet, mirror, etc.

[0175] Embodiments of the metasurface element material system

[0176] As described above, each individual metasurface element within any optical system, regardless of whether there are one or more metasurface elements including the system, has some specific 2D phase and the transmission function it performs

Number

[0177] Referring to FIG. 20, phase and transmission maps are provided for an embodiment of a metasurface device that includes silicon pillars embedded within SiO2. The upper left figure provides a heat map of transmission as a function of pillar diameter and height, and the color scale shown on the right. The upper right figure provides a phase map as a function of pillar diameter and height. The lower left provides a plot of a line scan of transmission as a function of pillar diameter at a fixed height of 600 nm. The lower right provides a plot of a line scan of relative phase as a function of pillar diameter for a fixed height of 600 nm. Using these figures, it will be appreciated that a particular set of pillar diameters and heights can be determined for specific transmission and phase over all appropriate wavelengths according to the embodiment, as well as a particular diameter for a height of 600 nm. In many embodiments, the pillar height can vary from 500 to 1000 nm, and the pillar diameter can vary from 100 to 300 nm. In various other embodiments, the pillar diameter can vary from 100 to 200 nm, and the pillar height can vary from 500 to 800 nm. In various other embodiments, at a pillar height of 600 nm, the pillar diameter can vary from 100 to 300 nm. The particular heights and diameters represent local optima for transmission of the device, but other pillar heights can be used as required by the design of a particular optical system in an embodiment.

[0178] Referring to FIG. 21, phase and transmission maps are provided for an embodiment of a metasurface element including silicon pillars in air. The upper left figure provides a heat map of transmission as a function of pillar diameter and height and the color scale shown on the right. The upper right figure provides a phase map as a function of pillar diameter and height. The lower left provides a line scan of transmission as a function of pillar diameter at a fixed height of 480 nm. The lower right provides a line scan of relative phase as a function of pillar diameter for a fixed height of 480 nm. Using these figures, it will be appreciated that a particular set of pillar diameters and heights can be determined for specific transmission and phase over all appropriate wavelengths according to the embodiment, as well as a specific diameter for a height of 480 nm. In many embodiments, the pillar height can vary from about 1 to 500 nm and the pillar diameter can vary from 100 to 350 nm. In various other embodiments, the pillar diameter can vary from 100 to 250 nm and the pillar height can vary from 150 to 500 nm. In various other embodiments, at a pillar height of 480 nm, the pillar diameter can vary from 100 to 280 nm. The particular heights and diameters represent local optima for the transmission of the element, but in embodiments, other pillar heights can be used as required by the design of a particular optical system.

[0179] Referring to FIG. 22, phase and transmission maps are provided for an embodiment of a metasurface device including TiO2 pillars in air. The upper left figure provides a heat map of transmission as a function of pillar diameter and height, and the color scale shown on the right. The upper right figure provides a phase map as a function of pillar diameter and height. The lower left figure provides a line scan of transmission as a function of pillar diameter at a fixed height of 975 nm. The lower right provides a line scan of relative phase as a function of pillar diameter for a fixed height of 975 nm. Using these figures, it will be understood that a particular set of pillar diameters and heights can be determined for specific transmission and phase over all appropriate wavelengths according to the embodiment, as well as a specific diameter for a height of 975 nm. In many embodiments, the pillar height can vary from 300 to 1000 nm, and the pillar diameter can vary from 100 to 350 nm. In various other embodiments, the pillar diameter can vary from 100 to 300 nm, and the pillar height can vary from 300 to 400 nm and / or from 700 to 1000 nm. In various other embodiments, at a pillar height of 975 nm, the pillar diameter can vary from 100 to 300 nm. The particular heights and diameters represent local optima for the transmission of the device, but in embodiments, other pillar heights can be used as required by the design of a particular optical system.

[0180] Referring to FIG. 23, phase and transmission maps are provided for an embodiment of a metasurface device including amorphous silicon pillars embedded within a benzocyclobutane (BCB) polymer. The upper figure provides a line scan of transmission as a function of pillar diameter at a fixed height of 590 nm and an element period of 400 nm. The lower figure provides a line scan of phase as a function of pillar diameter at a fixed height of 590 nm and an element period of 400 nm. Using these figures, it will be understood that a particular set of pillar diameters and heights can be determined for particular transmission and phase over all appropriate wavelengths according to the embodiment, as well as a particular diameter for a height of 590 nm. In many embodiments, at a pillar height of 975 nm, the pillar diameter can vary from 100 to 300 nm. In various other embodiments, the pillar diameter can vary from 100 to 225 nm. A particular height represents a local optimum for transmission of the device, although other pillar heights can be used as required by a particular optical system design.

[0181] Referring to FIG. 24, phase and transmission maps are provided for an embodiment of a metasurface device including amorphous silicon pillars embedded within silicon dioxide. The upper figure provides a line scan of transmission as a function of pillar diameter at a fixed height of 600 nm and an element period of 350 nm. The lower figure provides a line scan of phase as a function of pillar diameter at a fixed height of 600 nm and an element period of 350 nm. Using these figures, it will be understood that a particular set of pillar diameters and heights can be determined for particular transmission and phase over all appropriate wavelengths according to the embodiment, as well as a particular diameter for a height of 600 nm. In many embodiments, at a pillar height of 600 nm, the pillar diameter can vary from 100 to 275 nm. In various other embodiments, the pillar diameter can vary from 100 to 175 nm. A particular height represents a local optimum for transmission of the device, although other pillar heights can be used as required by a particular optical system design.

[0182] In other embodiments, tests were conducted on amorphous Si metasurface features embedded within SU8, and it was found that such surfaces having a pillar height of 675 nm and a pillar diameter of 100 - 300 are suitable for use. Additionally, amorphous Si metasurface features in air having a pillar height of 600 nm and a pillar diameter of 100 - 300 with an element spacing of 450 nm may be appropriate according to various embodiments.

[0183] While specific combinations of metamaterials and embedding materials have been described above, it will be understood that similar maps of metasurface features, transmittance, and phase may be created according to embodiments of the present invention.

[0184] Doctrine of equivalents As a result, although the invention has been described in a particular manner, many additional modifications and variations will be apparent to those skilled in the art. Therefore, it is understood that the invention may be practiced otherwise than as specifically described. Accordingly, the embodiments of the present invention are to be construed in all respects as illustrative and not as restrictive.

Claims

**Claim 1**: A meta-surface compatible lighting or sensor array, wherein the meta-surface compatible lighting or sensor array comprises: At least one light source or at least one sensor element; A plurality of meta-surface elements arranged in a planar array, wherein light emitted from the at least one light source or light impinging on each of the at least one sensor element passes through the planar array of the plurality of meta-surface elements; And; The plurality of meta-surface elements are configured to be asymmetric, and the plurality of meta-surface elements generate at least one of at least two far-field functions from the at least one light source or direct the light to at least one of the at least two far-field functions from the impinging light prior to illumination of the at least one sensor element based on the light passing through the plurality of meta-surface elements. A meta-surface compatible lighting or sensor array. **Claim 2**: The meta-surface compatible lighting or sensor array according to claim 1, wherein the asymmetry is a result of different pitches of the plurality of meta-surface elements along two orthogonal directions. **Claim 3**: The meta-surface compatible lighting or sensor array according to claim 1, wherein the at least two far-field functions have different polarizations. **Claim 4**: The meta-surface compatible lighting or sensor array according to claim 1, wherein the at least two far-field functions are linearly separated. **Claim 5**: A first spacer layer is disposed above the at least one light source, the first spacer layer is configured to cause divergence of the light emitted from the at least one light source or cause focusing of the light impinging on the at least one sensor element, and the plurality of meta-surface elements are disposed above the first spacer layer. The meta-surface compatible lighting or sensor array according to claim 1. **Claim 6**: The meta-surface compatible lighting or sensor array is: A second plurality of metasurface elements disposed at a distance from the first plurality of metasurface elements, wherein the second plurality of metasurface elements are configured to generate an additional far-field function on the bright field that impinges on the second plurality of metasurface elements, the second plurality of metasurface elements; A second spacer layer between the first plurality of metasurface elements and the second plurality of metasurface elements, wherein the separation distance is formed between the first plurality of metasurface elements and the second plurality of metasurface elements, the second spacer layer; The metasurface-corresponding illumination or sensor array according to claim 5, further comprising. **Claim 7** The metasurface-corresponding illumination or sensor array is At least one refractive lens separated from the first plurality of metasurface elements, wherein the at least one refractive lens is configured to collimate the at least one illumination source, the at least one refractive lens; A second spacer layer between the plurality of metasurface elements and the at least one refractive lens, wherein the separation distance is formed between the plurality of metasurface elements and the at least one refractive lens, the second spacer layer; The metasurface-corresponding illumination or sensor array according to claim 1, further comprising. **Claim 8** The at least one illumination source or the at least one sensor element comprises a plurality of illumination sources or a plurality of sensor elements arranged in a planar array, At least one of the plurality of metasurface elements is associated with each of the plurality of illumination sources or the plurality of sensor elements in an array of light emitted from each of the plurality of illumination sources or light impinging on each of the plurality of sensor elements, the metasurface-corresponding illumination or sensor array according to claim 1. **Claim 9** The at least one illumination source is polarized or not polarized, and the at least one illumination source is selected from the group consisting of VCSEL, solid-state laser, quantum cascade laser, LED, superluminescent LED, the metasurface-corresponding illumination or sensor array according to claim 1.

10. The at least two far-field functions are unique, the meta-surface-corresponding illumination or sensor array according to Claim 1.

11. The at least two far-field functions impose at least one dot pattern on the colliding light, the meta-surface-corresponding illumination or sensor array according to Claim 1.

12. The at least one dot pattern has up to 60,000 joining points, the meta-surface-corresponding illumination or sensor array according to Claim 11.

13. At least two patterns are imposed on the colliding light, the meta-surface-corresponding illumination or sensor array according to Claim 11.

14. At least the first dot pattern is configured to obtain measurements of the foreground of the scene, and at least the second dot pattern is configured to obtain measurements of the background of the scene, the meta-surface-corresponding illumination or sensor array according to Claim 13.

15. The at least two dot patterns are polarized diagonally with respect to each other, the meta-surface-corresponding illumination or sensor array according to Claim 13.

16. Three or more dot patterns having three or more different polarizations are imposed, the meta-surface-corresponding illumination or sensor array according to Claim 11.

17. The pattern is configured to be projected onto two different optical planes, the meta-surface-corresponding illumination or sensor array according to Claim 13.

18. A single platform imaging / detection system corresponding to a meta-surface element, wherein the single platform imaging / detection system corresponding to the meta-surface element is at least one sensor element and at least one illumination source, and At least one illumination metasurface element and at least one sensor metasurface element, wherein the at least one sensor metasurface element is disposed at a separation distance from the at least one illumination metasurface element, the at least one sensor metasurface element is disposed above the at least one sensor element, the at least one illumination metasurface element is disposed above the at least one light source, and each of the at least one illumination metasurface element and the at least one sensor metasurface element has at least one associated spacer layer, at least one illumination metasurface element and at least one sensor metasurface element, and Each of the plurality of metasurface elements comprises an array of metasurface features disposed on a substrate having translucency over a specified operating bandwidth, the array of metasurface features having a feature size smaller than the wavelength of light within the specified operating bandwidth, the at least one illumination metasurface element disposed in association with the at least one light source being configured to impose a radiation pattern on the bright field emitted from the at least one light source within the plane of the plurality of metasurface features, and the at least one sensor metasurface element disposed in association with the at least one sensor element being configured to receive the radiation pattern of the bright field after illumination of the scene. The at least one illumination metasurface element associated with the at least one light source generates at least one of two far-field functions on the bright field based on the light emitted from the at least one light source, and the at least one sensor metasurface element associated with the at least one sensor element directs the received light to at least one of the at least two far-field functions based on the received light, a single platform imaging / detection system corresponding to the metasurface element. **Claim 19**: The at least two far-field functions generate at least two patterns with orthogonal polarization, and the at least two far-field functions are linearly separated from each other on the bright field illuminating the scene so that three-dimensional information about the scene can be collected. The meta-surface-corresponding illumination or sensor array according to claim 16. **Claim 20**: The asymmetry is the result of the asymmetric cross-section of the plurality of meta-surface elements. The meta-surface-corresponding illumination or sensor array according to claim 1. **Claim 21**: The asymmetry is a further result of at least two different rotation angles of the plurality of meta-surface elements. The meta-surface-corresponding illumination or sensor array according to claim 20.

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