Transmission type metasurface lens integration

Abstract

The invention relates to transmissive metasurface lens integration. Metasurface elements, integrated systems combining such metasurface elements with light sources and / or detectors, and methods of making and operating such optical devices and integrated systems are provided. Systems and methods for integrating transmissive metasurfaces with other semiconductor devices or additional metasurface elements, especially such metasurfaces with substrates, illumination sources, and sensors, are also provided. The provided metasurface elements can 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 the light. In these embodiments, shaping emission and collection may be incorporated into separately co-designed detection and sensing optical systems.

Description

[0001] This application is a divisional application of the Chinese invention patent application with application date of August 31, 2018, application number 201880071477.5, and invention name “Transmission-type metasurface lens integration”. Technical Field

[0002] The present disclosure relates to optical devices incorporating metasurface elements, integrated systems incorporating light sources and / or detectors having such metasurface elements, and methods of manufacturing such optical devices and integrated systems. Background Art

[0003] Metasurface elements are diffractive optical devices in which the individual waveguide elements have sub-wavelength spacing and have a planar profile. Metasurface elements have recently been developed for use in the UV-IR band (300-10,000nm). Compared to traditional refractive optical devices, metasurface elements suddenly introduce phase shifts into the light field. This makes the thickness of the metasurface element approximately on the order of the wavelength of its designed operating wavelength, while the thickness of traditional refractive surfaces is 10-100 times (or more) greater than the wavelength of the light at which it is designed to operate. In addition, the thickness of the metasurface element does not vary among the constituent elements, so it is possible to shape the light without any curvature as required by refractive optical devices. Compared to traditional diffractive optical elements (DOEs) (such as binary diffractive optical elements), metasurface elements have the ability to impart a range of phase shifts on the incident light field. At least, the phase shift of the metasurface element can be at least between 0-2π, and there are at least 5 different values ​​within this range, while the binary DOE can only provide two different phase shift values ​​and is usually limited to a phase shift of 0 or 1π. Compared with multi-layer DOEs, metasurface elements do not need to change the height of their constituent elements along the optical axis, but only need to change the planar geometry of the metasurface element features. SUMMARY OF THE INVENTION

[0004] The present application relates to an optical device incorporating a metasurface element, an integrated system incorporating a light source and / or a detector having such a metasurface element, and a method for manufacturing such an optical device and integrated system.

[0005] Many embodiments are directed to a method of manufacturing one or more metasurface elements or systems, comprising:

[0006] depositing a layer of hard mask material on at least one surface of a substrate, wherein the substrate is transparent to light over a specified operating bandwidth;

[0007] depositing a pattern material layer on the hard mask material layer;

[0008] patterning the pattern material to form an array pattern atop the hard mask layer, the array pattern comprising one of a positive or negative replica of an array of metasurface features, the array of metasurface features comprising a plurality of metasurface features having a feature size less than a wavelength of light within a specified operating bandwidth and configured to impart a phase shift on impinging light within a plane of the plurality of metasurface features;

[0009] etching the hard mask layer using an anisotropic etching process to form a plurality of voids and raised features corresponding to the array pattern in the hard mask; and

[0010] Any remaining pattern material is removed from the top of the hard mask layer.

[0011] In various other embodiments, the substrate is formed of a material selected from the group consisting of fused silica, sapphire, borosilicate glass, and rare earth oxide glass.

[0012] In even various other embodiments, the hard mask material layer is formed from a material selected from the group consisting of silicon, various stoichiometric silicon nitrides, silicon dioxide, titanium dioxide, aluminum oxide, and is deposited using a deposition process selected from the group consisting of sputtering, chemical vapor deposition, and atomic layer deposition.

[0013] In various other embodiments, the pattern material layer is formed of one of a photoresist patterned using a photolithography process or a polymer patterned using a nanoimprint process.

[0014] In even yet various other embodiments, the array pattern is etched using a reactive ion etching process selected from the group consisting of: SF6, Cl2, BCl3, C4F8, or any static or multiplexed mixtures thereof.

[0015] In even yet various other embodiments, the residual pattern material is removed using a process selected from the group consisting of a chemical solvent, a chemical etchant, and a plasma etchant.

[0016] In even yet other various embodiments, the patterned hard mask material is a dielectric and forms metasurface features of the metasurface element.

[0017] In even yet various other embodiments, the method further comprises:

[0018] depositing a dielectric metasurface material layer on the patterned hard mask material layer such that the metasurface material layer fills voids in the hard mask material layer and extends over raised features of the hard mask material layer, thereby forming a blanket layer of metasurface material on top of the hard mask layer; and

[0019] The capping layer is planarized so that the metasurface material layer and the hard mask layer terminate at a uniform height above the substrate.

[0020] In even further various other embodiments, the metasurface material layer is formed of a material selected from silicon, silicon nitride of various stoichiometries, silicon dioxide, titanium dioxide, aluminum oxide, and is deposited using a conformal process selected from: chemical vapor deposition and atomic layer deposition.

[0021] In even yet various other embodiments, planarization uses an etching process selected from the group consisting of wet etching and plasma etching or a method in a chemical mechanical planarization technique.

[0022] In even further various other embodiments, a metasurface material disposed in the void forms a metasurface feature of the metasurface element, and wherein the hard mask material is configured as an embedded material having a lower refractive index than the metasurface material at the specified operating bandwidth.

[0023] In even yet various other embodiments, the hard mask material has negligible absorption over the designated operating bandwidth and has a refractive index between about 1 and about 2.4 at the designated operating bandwidth.

[0024] In even more various other embodiments, the method further comprises removing the hard mask material layer using selective etching, such that after removing the hard mask material layer, a metasurface material layer disposed in the voids of the patterned hard mask remains on the surface of the substrate to form a plurality of isolated metasurface features separated by a plurality of air gaps.

[0025] In even further various other embodiments, the method further comprises depositing an embedded material layer on the isolated metasurface features such that air gaps between the features are filled and such that the embedded material layer extends above the surface of the metasurface material layer, wherein the embedded material layer has a lower refractive index than the metasurface material at the specified operating bandwidth.

[0026] In even yet various other embodiments, the embedding material is a polymer selected from the group consisting of poly(methyl methacrylate), SU8, and benzocyclobutene.

[0027] In even yet various 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.

[0028] In even yet other various embodiments, the method further comprises planarizing the buried material layer such that the metasurface material layer and the buried material layer terminate at a uniform height above the substrate.

[0029] In even yet other various embodiments, the method further comprises depositing an anti-reflective coating on top of one or both of the embedding material layer and a side of the substrate disposed opposite the metasurface element.

[0030] In even yet various other embodiments, the antireflective coating consists of alternating layers of any combination of materials selected from silicon dioxide, titanium dioxide, aluminum oxide, silicon nitride, aluminum nitride, and amorphous silicon, wherein the thickness of each alternating layer is less than the wavelength of light within the operating bandwidth.

[0031] In even yet other embodiments, the substrate is one that is disposed on top of an illuminator or sensor, or is itself an illuminator or sensor.

[0032] In even yet other various embodiments, the substrate has a substrate thickness that is not suitable for use with the target optical system and further comprises at least one of:

[0033] removing at least a portion of the back side of the substrate by one or both of grinding or chemical etching; and

[0034] An additional substrate is aligned and fused to the substrate of the metasurface element.

[0035] In even further various other embodiments, the further substrate itself has a metasurface element disposed on one surface thereof, and wherein the substrate and the further substrate are fused along a surface opposite to the surface on which the opposing metasurface element is disposed.

[0036] In even yet various other embodiments, the fusion method uses a bonding process with a thermal budget below 600°C.

[0037] In even yet various other embodiments, the bonding process is a wafer bonding process using an adhesive selected from the group consisting of optical epoxy, benzocyclobutene, UV cured polymer, SU8, and plasma activated silica film.

[0038] In even yet various other embodiments, the method further comprises removing at least a portion of a backside of one or both substrates prior to fusing.

[0039] In even further various other embodiments, the method further comprises forming at least a first metasurface element on a first side of a first substrate, and forming at least a second metasurface element on a first side of a second substrate, and fusing the first and second substrates together along sides opposite to the first sides of the substrates using a bonding process having a thermal budget of less than 600°C.

[0040] In even yet other various embodiments, the plurality of metasurface features are non-uniform.

[0041] In even yet other various embodiments, the plurality of metasurface features deviate from an ideal shape by a predetermined amount based on a size of the metasurface features.

[0042] In even further various 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 less than or equal to the wavelength of light within the specified operating bandwidth such that the two layers of metasurface features operate together to apply a phase shift to the impinging light.

[0043] In even further various other embodiments, the plurality of metasurface features are non-uniform and deviate from an ideal shape by a predetermined amount based on a size of the metasurface feature, and wherein the ideal shape is a square, and wherein a side dimension of the ideal square is less than 200 nm, the metasurface features are formed as circles, and wherein a side dimension of the ideal square is less than 300 nm, the metasurface features are formed as squares with rounded edges.

[0044] In even yet various other embodiments, the method further comprises:

[0045] forming a plurality of identical or unique first metasurface elements;

[0046] providing a plurality of identical or unique illumination sources arranged in a planar array, and integrating at least one of a 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 and is thereby imparted with an angular deflection;

[0047] A first spacer layer is disposed between the planar array of illumination sources and the first metasurface element, the first spacer layer being configured to cause light emitted from each illumination source of the planar array to diverge before striking the corresponding first metasurface element,

[0048] 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 on a light field formed by emissions from all of the plurality of illumination sources; and

[0049] A second spacer layer is disposed between the first and second metasurface elements such that an offset distance is formed therebetween.

[0050] Various embodiments relate to a method of forming a plurality of metasurface elements, comprising: forming at least a first metasurface element on a first side of a first substrate, and forming at least a second metasurface element on a first side of a second substrate, and fusing the first and second substrates together along sides opposite to the first sides of the substrates using a bonding process with a thermal budget of less than 600°C.

[0051] In various other embodiments, the bonding process is a wafer bonding process using an adhesive selected from the group consisting of optical epoxy, benzocyclobutene, UV-curable polymer, SU8, and plasma activated silica film.

[0052] In even various other embodiments, the method further comprises removing at least a portion of a backside of one or both substrates prior to fusing.

[0053] In even various other embodiments, the method further comprises:

[0054] embedding and planarizing at least one of the first and second metasurface elements;

[0055] forming at least a third metasurface element on the first side of the third substrate; and

[0056] A side of the third substrate opposite the first side is fused to the planarized first or second metasurface using a bonding process with a thermal budget below 600°C.

[0057] In even other various other embodiments, the planarizing further comprises embedding at least one of the first and second metasurface elements in one of a polymer or a solid adhesive.

[0058] In even various other embodiments, the method further comprises iteratively forming, embedding, and fusing steps to form a layered stack of four or more metasurface elements.

[0059] In even other various other embodiments, at least one layer at one end of the layered stack is one of an illuminator or a sensor.

[0060] In even other various other embodiments, the method further comprises:

[0061] inserting a spacer substrate between sides of the first and second substrates opposite the metasurface element, the spacer substrate having at least one hole disposed therethrough; and

[0062] The spacer substrate is fused to the first and second substrates using a bonding process having a thermal budget below 600° C. such that the at least one hole forms an air gap between the first and second substrates.

[0063] In even other various other embodiments, the spacer substrate is made of a low refractive index material selected from the group consisting of polymer, SiO2 and glass.

[0064] In even various other embodiments, the spacer material is coated with black chrome.

[0065] In even various other embodiments, the method further comprises iteratively forming, inserting, and fusing steps to form a layered stack of three or more metasurface elements.

[0066] In even other various other embodiments, at least one layer at one end of the layered stack is one of an illuminator or a sensor.

[0067] In even various other embodiments, the plurality of metasurface features are non-uniform.

[0068] In even other various other embodiments, the plurality of metasurface features deviate from an ideal shape by a predetermined amount based on a size of the metasurface features.

[0069] Another embodiment is directed to a method of forming a composite metasurface element, comprising: forming two layers of metasurface features on top of a substrate, wherein the two layers are offset from each other by a distance less than or equal to the wavelength of light within the specified operating bandwidth, so that the two layers of metasurface features operate together to apply a phase shift to the impinging light.

[0070] Another embodiment is directed to a method of forming a metasurface element, comprising:

[0071] forming a plurality of identical or unique first metasurface elements;

[0072] providing a plurality of identical or unique illumination sources arranged in a planar array, and integrating at least one of a 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 and is thereby imparted with an angular deflection;

[0073] Disposing a first spacer layer between the planar array of illumination sources and the first metasurface element, the first spacer layer being configured to cause light emitted from each illumination source of the planar array to diverge before striking the corresponding first metasurface element;

[0074] 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 on a light field formed by emissions from all of the plurality of illumination sources; and

[0075] A second spacer layer is disposed between the first and second metasurface elements such that an offset distance is formed therebetween.

[0076] In yet other embodiments, at least the first spacer layer comprises a solid state material.

[0077] In yet other embodiments, at least the second spacer layer includes an air gap.

[0078] In even yet other embodiments, the plurality of metasurface features are non-uniform.

[0079] In even yet other embodiments, the plurality of metasurface features deviate from an ideal shape by a predetermined amount based on a size of the metasurface features.

[0080] In even yet other embodiments, the method further comprises:

[0081] forming a plurality of identical or unique first metasurface elements;

[0082] 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 a plurality of sensor elements in the array such that light incident on each of the plurality of sensor elements passes through at least one of the first metasurface elements and is thereby imparted with an angular deflection;

[0083] Disposing a first spacer layer between the planar array of sensor elements and the first metasurface element, the first spacer layer being configured to cause light impinging on each first metasurface element to diverge before impinging on a corresponding sensor element of the planar array;

[0084] 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 on a light field impinging thereon; and

[0085] A second spacer layer is disposed between the first and second metasurface elements such that an offset distance is formed therebetween.

[0086] Various other embodiments relate to a method of forming a metasurface element, comprising:

[0087] forming a plurality of identical or unique first metasurface elements;

[0088] 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 a plurality of sensor elements in the array such that light incident on each of the plurality of sensor elements passes through at least one of the first metasurface elements and is thereby imparted with an angular deflection;

[0089] Disposing a first spacer layer between the planar array of sensor elements and the first metasurface element, the first spacer layer being configured to cause light impinging on each first metasurface element to diverge before impinging on a corresponding sensor element of the planar array;

[0090] 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 on a light field impinging thereon; and

[0091] A second spacer layer is disposed between the first and second metasurface elements such that an offset distance is formed therebetween.

[0092] Several embodiments relate to metasurface elements, including:

[0093] an array of metasurface features disposed atop a substrate that is transparent to light over a specified operating bandwidth, the array comprising a plurality of metasurface features having a feature size that is smaller than a wavelength of light within the specified operating bandwidth and configured to impart a phase shift on impinging light within a plane of the plurality of metasurface features;

[0094] The plurality of metasurface features are non-uniform and deviate from an ideal shape by a predetermined amount based on a size of the metasurface features.

[0095] In some other embodiments, the ideal shape is a square, and wherein the side dimension of the ideal square is less than 200 nm, the metasurface features are formed as circles, and wherein the side dimension of the ideal square is less than 300 nm, the metasurface features are formed as squares with rounded edges.

[0096] Various embodiments relate to metasurface-enabled illumination or sensor arrays, including:

[0097] multiple identical or unique illumination sources or sensor elements arranged in a planar array;

[0098] a first spacer layer disposed above the planar array of illumination sources and configured to produce divergence in light emitted from each illumination source of the planar array, or convergence in light incident on each sensor element;

[0099] a plurality of identical or unique first metasurface elements disposed above the first spacing layer, at least one of the plurality of first metasurface elements being associated with each of a plurality of illumination sources or sensor elements in the array such that light emitted from each of the plurality of illumination sources or light incident on each of the plurality of sensor elements passes through at least one of the first metasurface elements, thereby imparting an angular deflection;

[0100] 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 on a light field impinging thereon; and

[0101] A second spacer layer is disposed between the first and second metasurface elements such that an offset distance is formed therebetween.

[0102] In various other embodiments, the plurality of metasurface features on each metasurface element are non-uniform and deviate from an ideal shape by a predetermined amount based on the size of the metasurface features.

[0103] In even various other embodiments, multiple 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 rotation angles, so that the metasurface element is configured to imprint at least two patterns with orthogonal polarizations and linearly offset from each other on the illumination source, or detect such patterns from the impinging light before illumination by the sensor element, and the array is configured so that the array obtains three-dimensional information from the scene in a single shot.

[0104] In various other embodiments, the illumination source is 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.

[0105] In even yet other various embodiments, both patterns are unique.

[0106] In even yet various other embodiments, both patterns have at least 50,000 bonding points.

[0107] In even yet other embodiments, at least a first pattern is configured to capture a measure of a foreground of a scene, and wherein at least a second pattern is configured to capture a measure of a background of the scene.

[0108] In even yet various other embodiments, the two patterns are diagonally polarized with respect to the laser polarization.

[0109] In even yet various other embodiments, more than two patterns having more than two different polarizations are used.

[0110] Additional embodiments relate to metasurface element-enabled sensors, including:

[0111] at least one sensor element;

[0112] at least one first and at least one second metasurface element, disposed at an offset distance above at least one sensor element, and having a first spacer layer disposed therebetween;

[0113] wherein each of the at least one first and second metasurface elements comprises an array of metasurface features disposed atop at least one substrate transparent to light over a specified operating bandwidth, the array comprising a plurality of metasurface features having a feature size less than a wavelength of light within the specified operating bandwidth and configured to impart a phase shift on impinging light within a plane of the plurality of metasurface features; and

[0114] The array of metasurface features on each of the at least one first and second metasurface elements is configured to focus light of a specified operating bandwidth over a specified field of view and to move incident light so that it strikes the sensor element at a chief ray angle of zero or near zero degrees.

[0115] In various other embodiments, the first spacer layer is one of a solid spacer material or an air gap.

[0116] In even various other embodiments, the field of view is ±44 degrees.

[0117] In even various other embodiments, the sensor further comprises a narrow bandwidth filter disposed between the metasurface element and the sensor element.

[0118] In even various other embodiments, the narrow bandwidth filter is comprised of alternating layers of low and high refractive index selected from silicon dioxide, titanium dioxide, amorphous silicon, silicon nitride, and aluminum oxide.

[0119] In even other various other embodiments, the sensor further comprises a plurality of identical microlenses disposed between the metasurface element and the sensor element.

[0120] In even other various other embodiments, 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 wherein the substrate comprises the first spacer layer.

[0121] In even other various other embodiments, the heights of the two metasurface elements on both sides of the substrate are the same.

[0122] In even other various other embodiments, the two metasurface elements are formed from films deposited simultaneously on the front and back surfaces of the same substrate using a conformal deposition process selected from pressure chemical vapor deposition and atomic layer deposition.

[0123] In even other various other embodiments, the at least one first metasurface element and the at least one second metasurface element are arranged to face inwardly from each other on separate substrates separated by an air gap.

[0124] In even other various other embodiments, the sensor further comprises an optical bandpass filter integrated in the outwardly facing surface of the substrate of the at least one second metasurface.

[0125] In even various other embodiments, the sensor further comprises at least a third metasurface element disposed between the first and second metasurface elements and the CMOS sensor and configured to angularly diverge the path of the incident light such that a chief ray angle of the light striking the CMOS sensor is non-zero.

[0126] In even other various other embodiments, at least three metasurfaces are configured to minimize mesh distortion to less than 5% within a specified field of view.

[0127] In even other various other embodiments, the sensor element is a CMOS sensor.

[0128] Additional embodiments relate to a single-platform imaging / sensing system enabled with a metasurface element, comprising:

[0129] at least one sensor element and at least one illumination source;

[0130] at least one separate metasurface element disposed at an offset distance above each of the at least one sensor element and the at least one illumination source and each having at least one spacer layer;

[0131] wherein each metasurface element comprises an array of metasurface features disposed atop a substrate that is transparent to light over a specified operating bandwidth, the array comprising a plurality of metasurface features having a feature size that is smaller than a wavelength of light within the specified operating bandwidth, and wherein at least one illumination metasurface element disposed in association with the illumination source is configured to impose a radiation pattern on a light field emitted therefrom within a plane of the plurality of metasurface features, and wherein 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 light field after scene illumination.

[0132] In even further embodiments, the system further includes a plurality of separate metasurface elements and spacer layers associated with each of the illumination source and sensor elements.

[0133] In even further embodiments, a metasurface element associated with the illumination source imposes two orthogonal polarizations on the light field to produce at least two patterns having orthogonal polarizations and linearly offset from each other on the light field of the illuminated scene, and wherein the metasurface element associated with the sensor element is configured to detect at least two patterns, enabling collection of three-dimensional information about the scene.

[0134] Various embodiments are directed to a method of manufacturing a metasurface element for imprinting a desired far-field intensity on an illumination source, comprising:

[0135] Calculate the far field of the illumination source;

[0136] calculating a far field of a target, wherein the target is a metasurface element;

[0137] Calculating a least square fit of the target far field to obtain a pseudo far field, so that a convolution of the pseudo far field and the illumination source far field produces a target far field;

[0138] Setting the initial metasurface feature array grid and phase as initial conditions;

[0139] determining one or more target cost functions and calculating a gradient function of each of the one or more cost functions for each of a plurality of pixels of the metasurface element;

[0140] inputting the results of the one or more logarithmic functions and the gradient function into an optimization algorithm;

[0141] updating the phase for each of a plurality of pixels of the metasurface element, and repeating the gradient calculation and optimization until the target cost function converges; and

[0142] Output the calculated metasurface element phase profile.

[0143] In various other embodiments, the cost function is selected from: the squared distance to the target, 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.

[0144] In even various other embodiments, the optimization algorithm is one of conjugate gradient or L-Broyden-Fletcher-Goldfarb-Shannon.

[0145] Various embodiments also relate to a method of forming a metasurface element on a substrate, comprising a plurality of metasurface features having a feature size less than a wavelength of light within a specified operating bandwidth and configured to impart a phase shift on impinging light within a plane of the plurality of metasurface features, wherein the substrate has a substrate thickness that is not suitable for use with a target optical system, and further comprising at least one of the following:

[0146] removing at least a portion of the back side of the substrate by one or both of grinding or chemical etching; and

[0147] An additional substrate is aligned and fused to the substrate of the metasurface element.

[0148] In some other embodiments, the further substrate itself has a metasurface element disposed on one surface thereof, and wherein the substrate and the further substrate are fused along a surface opposite to the surface on which the opposing metasurface element is disposed.

[0149] In even various other embodiments, the fusion method uses a bonding process with a thermal budget below 600°C.

[0150] In even various other embodiments, the bonding process is a wafer bonding process using an adhesive selected from the group consisting of optical epoxy, benzocyclobutene, UV-curable polymer, SU8, and plasma-activated silica film.

[0151] In even several other embodiments, the method further comprises removing at least a portion of a backside of one or both substrates prior to fusing.

[0152] In even several other embodiments, the method further includes forming at least a first metasurface element on a first side of a first substrate, and forming at least a second metasurface element on a first side of a second substrate, and fusing the first and second substrates together along sides opposite to the first sides of the substrates using a bonding process having a thermal budget of less than 600°C.

[0153] In even several other embodiments, the plurality of metasurface features are non-uniform.

[0154] In even several other embodiments, the plurality of metasurface features deviate from an ideal shape by a predetermined amount based on a size of the metasurface features.

[0155] In even several other embodiments, the method further comprises:

[0156] embedding and planarizing at least one of the first and second metasurface elements;

[0157] forming at least a third metasurface element on the first side of the third substrate; and

[0158] A side of the third substrate opposite the first side is fused to the planarized first or second metasurface using a bonding process with a thermal budget below 600°C.

[0159] In even several other embodiments, the planarizing further comprises embedding at least one of the first and second metasurface elements in one of a polymer or a solid adhesive.

[0160] In even several other embodiments, iterative forming, embedding, and fusing steps are included to form a layered stack of four or more metasurface elements.

[0161] In even several other embodiments, at least one layer at one end of the layered stack is one of an illuminator or a sensor.

[0162] In even several other embodiments, the method further comprises:

[0163] inserting a spacer substrate between sides of the first and second substrates opposite the metasurface element, the spacer substrate having at least one hole disposed therethrough; and

[0164] The spacer substrate is fused to the first and second substrates using a bonding process having a thermal budget below 600° C. such that the at least one hole forms an air gap between the first and second substrates.

[0165] Various other embodiments relate to metasurface elements, including:

[0166] An array of metasurface features disposed on top of a substrate that is transparent to light over a specified operating bandwidth, the array comprising a plurality of metasurface features having a feature size that is smaller than a wavelength of light within the specified operating bandwidth and configured to impart a phase shift on impinging light within a plane of the plurality of metasurface features, and wherein the plurality of metasurface features consist of one of:

[0167] Amorphous-Si metasurface features embedded in SiO2 with pillar heights of 500 to 1000 nm and pillar diameters of 100 to 300 nm;

[0168] Amorphous-Si metasurface features embedded in SiO2 with pillar heights of 600nm and pillar diameters ranging from 100 to 300nm;

[0169] amorphous-Si metasurface features with air gaps disposed therebetween, and pillar heights of 1 to 500 nm and pillar diameters of 100 to 350 nm;

[0170] amorphous-Si metasurface features with air gaps disposed therebetween, and pillar heights of 480 nm and pillar diameters of 100 to 280 nm;

[0171] TiO2 metasurface features with air gaps disposed therebetween, and pillar heights of 300 to 1000 nm and pillar diameters of 100 to 350 nm;

[0172] TiO2 metasurface features with air gaps disposed therebetween, and pillar heights of 975nm and pillar diameters of 100 to 300nm;

[0173] Amorphous-Si metasurface features embedded in benzocyclobutane with a pillar height of 590 nm and a pillar diameter of 100 to 300 nm;

[0174] Amorphous-Si metasurface features embedded in SiO2 with pillar heights of 600nm and pillar diameters ranging from 100 to 275nm;

[0175] Amorphous-Si metasurface features embedded in SU8 with a pillar height of 675 nm and a pillar diameter of 100 to 300 nm; and

[0176] Amorphous-Si metasurface features in air with 600nm pillar height and pillar diameters ranging from 100 to 300nm and 450nm element pitch.

[0177] In many other embodiments where amorphous silicon is selected, the amorphous silicon may be hydrogenated, resulting in higher optical transmittance compared to amorphous silicon where hydrogen is not present in the structure.

[0178] Additional embodiments and features are partially set forth in the following description, and will become partially apparent to those skilled in the art upon reading the specification, or may be learned through practice of the present disclosure. A further understanding of the nature and advantages of the present disclosure may be achieved by reference to the remainder of the specification and drawings which constitute a part of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0179] This description will be more fully understood with reference to the following drawings, which are presented as exemplary embodiments of the invention and are not to be construed as a complete description of the scope of the invention, wherein:

[0180] Figures 1A to 1G A schematic diagram illustrating a process of manufacturing a metasurface element according to an embodiment of the present invention is provided.

[0181] Figure 2A A schematic diagram is provided showing an embedded metasurface element with an anti-reflective coating according to an embodiment of the present invention.

[0182] Figure 2B A schematic diagram is provided showing a planarized embedded metasurface element with an anti-reflective coating according to an embodiment of the present invention.

[0183] Figure 3 A schematic flow chart illustrating a process for fabricating a metasurface element according to an embodiment of the present invention is provided.

[0184] FIG. 4A to FIG. 4C Schematic diagrams of metasurface elements with varying cross-sectional features are provided according to embodiments of the present invention.

[0185] Figure 5 Schematic diagrams showing the combination of multiple substrates with metasurface elements according to embodiments of the present invention are provided.

[0186] Figure 6 Schematic diagrams are provided showing the combination of multiple substrates with multiple metasurface elements according to embodiments of the present invention.

[0187] Figure 7 Schematic diagrams are provided showing the combination of multiple substrates having multiple air-gap-introduced metasurface elements according to embodiments of the present invention.

[0188] Fig. 8A Schematic diagrams are provided showing metasurface elements incorporating spacers integrated with sensor / illuminator components according to embodiments of the present invention.

[0189] Figure 8B A schematic diagram showing a metasurface element incorporating a spacer according to an embodiment of the present invention is provided.

[0190] Fig. 9 Schematic diagrams showing a plurality of metasurface element substrates according to embodiments of the present invention are provided.

[0191] Fig. 10A A flow chart is provided for generating an arbitrary radiation pattern from a VCSEL or VCSEL array using a metasurface element according to an embodiment of the present invention.

[0192] Fig. 10B and 10C Provided is a method of using the method according to an embodiment of the present invention Fig. 10A Phase (10B) and intensity (10C) diagrams obtained using the method.

[0193] Fig.11 Schematic diagrams are provided showing an array metasurface element coupled to a set of pixelated sensor elements or illumination sources (incorporating a second metasurface into an integrated package) according to embodiments of the present invention.

[0194] FIG. 12A to FIG. 12C A schematic diagram is provided showing a polarization-splitting metasurface element that produces two unique radiation patterns in a VCSEL array according to an embodiment of the present invention.

[0195] Fig.13 A schematic diagram is provided showing two metasurface elements combined with a second element (e.g., a cutoff filter) according to an embodiment of the present invention, wherein the chief ray angle of the focused light is 0 degrees relative to the filter plane.

[0196] Fig.14 A schematic diagram is provided showing a system of two metasurface elements according to an embodiment of the present invention, wherein each metasurface element is formed on a unique substrate.

[0197] Fig.15 A schematic diagram is provided showing a system of three metasurface elements designed to correct multiple monochromatic aberrations according to an embodiment of the present invention.

[0198] Fig.16 A schematic diagram is provided showing a method for generating a plurality of pixels at an image sensor plane and a plurality of pixels at a plurality of image sensor planes according to an embodiment of the present invention. Fig.15 The image height of the metasurface element system as a function of the chief ray angle.

[0199] Fig.17 Provided are diagrams showing embodiments according to the present invention. Fig.15 Schematic diagram of an example of mesh distortion of a metasurface element system.

[0200] Fig.18 A schematic diagram is provided showing an integrated system with metasurface elements on the illuminator and detector according to an embodiment of the present invention.

[0201] Fig.19 A schematic diagram is provided showing an integrated system with metasurface elements on the illuminator and detector according to an embodiment of the present invention, where the polarization of the light provides an additional degree of freedom.

[0202] Fig. 20 Data graphs are provided showing the phase and transmission response of a metasurface feature according to an embodiment of the present invention, the metasurface feature comprising cylindrical pillars composed of amorphous silicon embedded in SiO2.

[0203] Fig.21 Data graphs showing the phase and transmission response of metasurface features comprising cylindrical posts composed of amorphous silicon are provided in accordance with embodiments of the present invention.

[0204] Fig. 22 Data graphs are provided showing the phase and transmission response of a metasurface feature according to an embodiment of the present invention, the metasurface feature comprising cylindrical pillars composed of amorphous TiO2 in air.

[0205] Fig.23 Data graphs are provided showing the phase and transmission response of a metasurface feature comprising cylindrical posts composed of amorphous silicon encapsulated in a polymer at a wavelength of 850 nm according to an embodiment of the present invention.

[0206] Fig.24 Data graphs are provided showing the phase and transmission response of a metasurface feature according to an embodiment of the present invention, the metasurface feature comprising cylindrical posts composed of Si encapsulated in SiO2 at a wavelength of 850 nm. DETAILED DESCRIPTION OF THE INVENTION

[0207] Now answering the accompanying drawings, metasurface elements, integrated systems combining such metasurface elements with light sources and / or detectors, and methods of manufacturing and operating such optical devices and integrated systems are provided. Various embodiments relate to systems and methods for integrating transmissive metasurface elements with other semiconductor devices or additional metasurface elements, and more specifically to integrating such metasurfaces with substrates, illumination sources, and sensors. In some embodiments, the metasurface element can be used to use the polarization of light to shape the output light from the illumination source or to collect light reflected from the scene, thereby forming two unique patterns. In these embodiments, the shaped emission and collection can be combined into a single co-designed detection and sensing optical system.

[0208] In various embodiments, the metasurface element can introduce a multilayer metasurface element comprising a combination of two or more metasurface optical elements. In various such embodiments, the multilayer metasurface element can be independent (i.e., not directly integrated into the system with a specific illuminator or sensor). In some such embodiments, the optical system can be composed of a single physical component or a substrate with a metasurface element (the metasurface element is located on either side). In some embodiments, multiple substrates with multiple metasurface elements can be combined to form a more complex system. In these embodiments, the thickness of the substrate can be determined by the requirements of the optical system, manufacturing constraints, and the specific 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 these substrates together by suitable techniques (e.g., wafer bonding, optical adhesives). However, in general, according to the embodiment, any number of metasurface elements can be combined by any number of steps using CMOS or related processes.

[0209] In various embodiments, the metasurface elements may be freestanding, or may be embedded in another material. In various embodiments, the choice of embedding material includes appropriate selection of refractive index and absorption properties. In various such embodiments, the embedding material may provide mechanical stability and protection, as well as additional design freedom to enable the metasurface to perform the desired optical function.

[0210] In various embodiments, metasurface elements can be mounted or fabricated in arrays directly on the LEDs, VCSEL faces, or each face of the VCSELs to minimize device thickness and optimize alignment of the metasurface illuminator / sensor. In some such embodiments, the resulting system can be used to convert a natural Lambertian or some arbitrary light distribution to a wide range and essentially arbitrary light distribution, including, for example, a so-called top hat, a so-called batwing profile, or any other desired structured light pattern.

[0211] In some embodiments, a spacer layer of defined thickness (e.g., working distance) can be deposited on a CMOS image sensor, LED, VCSEL, etc. to achieve an optical distance suitable for a desired camera design, illuminator design, or optimal system performance. In various embodiments, the spacer layer material can be organic or inorganic and can have a lower refractive index than the dielectric elements that make up the metasurface. In some such embodiments, the thickness of the spacer layer can be modified to provide appropriate optical spacing for a particular optical system.

[0212] Various embodiments also relate to methods for manufacturing metasurface elements. In some such embodiments, the method involves manufacturing metasurface elements on a wafer incorporating other devices (e.g., sensors or illuminators), thereby avoiding expensive manufacturing processes in some embodiments, such as mechanical assembly of small-size elements or active alignment of optical elements with sensors. In some such embodiments, the metasurface element can be integrated with the sensor (or illuminator) in a series of operations in a semiconductor factory. In many such embodiments, the sequence may include: (i) sensor or illuminator; (ii) optional microlens array / collimator, optional filter, optional spacer layer, optional metasurface element, optional additional spacer layer, optional metasurface element, optional anti-reflection (AR) layer, optional protective layer. In many such embodiments, a series of elements may include: (i) sensor or illuminator; (ii) optional microlens array / collimator, optional filter, optional spacer layer, optional metasurface element, optional additional spacer layer, optional metasurface element, optional anti-reflection (AR) layer, optional protective layer.

[0213] Embodiments of manufacturing metasurface elements

[0214] Currently, the manufacture of metasurface elements requires the use of specialized processes and systems that are incompatible with large-scale manufacturing, thereby limiting the implementation and adoption of such metasurface elements in CMOS devices. An exemplary description of conventional methods for forming metasurface elements 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 produce metasurfaces through standard semiconductor processes will enable the direct integration of metasurface optical devices with functional elements, such as light emitting diodes (LEDs), vertical cavity surface emitting lasers (VCSELs), complementary metal oxide semiconductor (CMOS) image sensors, microelectromechanical (MEM) devices, etc., where direct integration refers to combining metasurface elements and sensors / illuminators using the same or similar unit processes as those used to manufacture functional CMOS elements.

[0215] Thus, various embodiments are directed to methods for fabricating metasurface components and systems, and more particularly to methods that can be implemented within conventional semiconductor foundries. In various embodiments, conventional processes suitable for fabricating metasurface components may include photolithography, nanoimprinting, various chemical vapor deposition (CVD), atomic layer deposition (ALD), and physical vapor deposition (PVD) mass transfer processes, as well as chemical and plasma etching (and CMC), among others. Turning to the accompanying drawings, in Figures 1A to 1G A set of exemplary manufacturing processes tailored for the manufacture of various aspects of embodiments of a metasurface element are shown in the schematic diagram of .

[0216] Metasurface optical components are constructed from dielectric materials with feature sizes ranging from 10 nanometers to micrometers, or often smaller than the wavelength of light using the metasurface. Figures 1A to 1C In various embodiments, the initial steps in manufacturing a metasurface element include patterning and forming an array of metasurface features. In various such embodiments, Figure 1A As shown, the metasurface feature formation process is completed by depositing a patterned material (14) on a suitable hard mask material (12) (itself placed on a suitable substrate (10)) with a thickness t (t is the thickness of the film and the height of the final metasurface). These layers can be formed using any suitable deposition technique, including, for example, sputtering, chemical vapor deposition (CVD) or atomic layer deposition (ALD).

[0217] Although exemplary materials will be discussed with respect to specific embodiments throughout this disclosure, it should be understood that any suitable combination of patterning materials, hard mask materials, and substrates can be used for these purposes. For example, in various embodiments, the substrate material is selected to provide suitable structural support and be transparent to light of the desired bandwidth. Exemplary substrate materials that have been successfully implemented using the methods described in the embodiments include, for example, fused quartz, sapphire, borosilicate glass, and rare earth oxide glass. Similarly, the hard mask material can be selected from any readily available material suitable for semiconductor foundries. Exemplary hard materials include, for example, silicon, various stoichiometric silicon nitrides, silicon dioxide, titanium dioxide, aluminum oxide, and the like. In various embodiments, for example, in the case where the hard mask material forms an embedded material (as described in more detail below), the hard mask material can be selected to have a lower refractive index (e.g., from 1 to 2.4) at a specific wavelength of light. Finally, the patterning material according to the embodiment can be formed by any suitable photoresist, for example, a photocrack agent tuned for the lithography wavelength capable of forming a super surface feature of a desired size. Exemplary photolithography processes include, for example, ultraviolet and deep ultraviolet (DUV) lithography. In other embodiments, the patterned layer can be a polymer material suitable for nanoimprint lithography. Regardless of the specific material used, the patterned material must be able to reproduce the desired feature pattern from 10 nanometers to micrometers, and must properly protect the underlying hard mask film in selected areas during subsequent steps.

[0218] In particular, if Figure 1B As shown, once the substrate (10), hard mask (12), and patterning material (14) layers are in place, the patterning material is patterned to reproduce an array of features (16) corresponding to a negative or positive reproduction of the final expected metasurface feature array structure. The process of generating the feature pattern can take any form suitable for generating the desired feature size. For example, in embodiments of metasurface elements for visible light or near-infrared applications, UV lithography can be used (e.g., where the operating wavelength of the UV lithography step is below 193nm). In even other embodiments, the pattern can be physically imprinted by a master stamper in a nanoimprint lithography process.

[0219] like Figure 1CAs shown, once the desired feature array pattern (16) is in place, an anisotropic etching process is used to transfer the desired feature pattern into the hard mask layer (12). An exemplary anisotropic etching process used in accordance with an embodiment is a reactive ion etching process. It will be appreciated that a variety of possible chemicals may be used in the reactive ion etching process, including, for example, SF6 gas, Cl2 gas, BCl3 gas, C4F8, or any mixture of these gases. In addition, the gas mixture may be static or timed, wherein one or more gases are introduced and then a second unique gas or gases are introduced after a certain period of time. Regardless of which specific anisotropic etching process is used, once the pattern is etched into the hard coating, the remaining photoresist may be removed using any suitable method (e.g., chemical solvents, chemical etchants, plasma etchants, etc.). Note that in various embodiments, it may be desirable to use the feature array (16) formed in the hard mask material (14) as the final metasurface element. In these embodiments, the process may be stopped here, or, for example, the process may be continued. Figure 1G in combination with the deposition of a suitable AR coating or mechanically protective embedding layer as described above.

[0220] like Figure 1D As shown, in which a particular metasurface material will be used in the final metasurface element, a feature pattern (16) formed in the etched hard mask (12) (such as in Figure 1C ) can be used as a template in the final metasurface structure. In these embodiments, the separated 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 produce a metasurface element. As shown, the metasurface material (18) fills the space formed by the feature pattern (16) etched in the hard mask (12), thereby completely filling the gap. In addition to filling the gap (20), this process also leaves a capping layer of the metasurface material above the remaining hard mask. Again, although specific metasurface materials will always be discussed, it will be understood that the metasurface material according to the embodiment can be selected from any readily available dielectric material having a desired refractive index and suitable for use in a semiconductor foundry. Exemplary metasurface materials include, for example, silicon, various stoichiometric silicon nitrides, silicon dioxide, titanium dioxide, aluminum oxide, etc.

[0221] refer to Figure 1EOnce the excess fill of the metasurface material (18) is deposited, etching or chemical mechanical planarization can be performed to remove the excess fill layer depending on the embodiment, thereby providing a uniform height for the patterned hard mask (12) and the metasurface material (12). In embodiments where an embedded metasurface material is required, and where a suitable hard coating material has been selected as the embedding material (as previously described), the process can be stopped and the resulting metasurface material with the embedded hard coating material structure can be used as the final metasurface element. The metasurface element can then be optionally coated with a suitable AR coating or mechanical protection layer, as described below.

[0222] In various embodiments, such as Figure 1E As shown, the hard mask material (12) is removed, thereby leaving an independent metasurface element (20). In these embodiments, a selective etching chemical method can be used to remove the hard mask, which etches the hard mask material (12) at a much higher rate than the metasurface material (18) (e.g., 100:1 or 1000:1 or higher). As will be appreciated by those skilled in the art, such a process depends on the specific selection of the metasurface material and the hard mask material. For example, in an embodiment in which the hard mask is silicon and the metasurface is TiO2, the XeF2 etching chemistry will selectively remove silicon while leaving the metasurface material substantially unchanged. Note that in embodiments in which the metasurface element is designed to be independent, that is, the metasurface element features protrude from the ends of the substrate, with only air gaps (22) separating them, the process is completed at this step.

[0223] Finally, as mentioned previously, in certain embodiments where a metasurface with an AR coating or mechanical protection layer is desired, additional steps may be required to complete the final metasurface element. Figure 1G In various embodiments, an AR coating or mechanical protection layer or planarization layer (24) may also be deposited to fill the gaps (22) between the metasurface features (20) and extend above 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 a suitable refractive index and minimal light absorption at a desired wavelength or bandwidth of interest (a planarization layer can provide a multi-layer metasurface element for a complex optical system) may be used in this process.

[0224] As described above, in order to protect the metasurface and provide improved functionality, in many embodiments, the metasurface components and substrate surface are coated with one or more materials or material layers. Figure 2A, showing a schematic diagram of an embedded metasurface. As shown, the metasurface features (20) can be any material having the desired optical properties as described above, embedded in an embedding medium (24) that typically has a lower 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 refractive index embedding medium encapsulates the metasurface features and may extend a certain thickness above the metasurface features. In these embodiments, the low refractive index medium may act as a protective barrier (i.e., provide mechanical stability) for the metasurface elements. The embedding material may also provide additional design freedom for the system, which allows certain properties to be optimized, such as to improve the overall transmittance or efficiency of the metasurface, and in some cases, a separate AR coating is not required. The embedded metasurface is shown here to be fabricated on a substrate, but the metasurface may also extend from the sensor / illuminator, as described in detail below. The combined elements (metasurface, embedding medium, and substrate) may also be coated with a suitable anti-reflection coating on the side of the substrate comprising the metasurface (26') and / or on the back side of the substrate (26). In various embodiments, the AR coating may include alternating layers of any combination of silicon dioxide, titanium dioxide, aluminum oxide, silicon nitride, aluminum nitride, or amorphous silicon, wherein the thickness of each layer is less than the wavelength of light within the operating range of the metasurface. Additionally, as described above, the embedding medium itself may potentially function as an anti-reflection coating.

[0225] Although certain embedded metasurface embodiments are described above, in various other embodiments, such as Figure 2B As shown, the metasurface can be embedded and planarized. In these embodiments, the metasurface elements can be embedded in a suitable low refractive index material (as described above), and then the embedding medium (24) can be etched or planarized in a separate step to a height commensurate with the metasurface elements (20). An optional anti-reflective coating can also be included on the exposed substrate surface (26) or on the patterned metasurface side (not shown).

[0226] Embodiments of manufacturing metasurface elements on conventional substrates

[0227] Although the above discussion has described in detail a manufacturing process that can form a variety of free-standing or embedded metasurface elements using conventional CMOS manufacturing techniques, it may not be practical to adapt conventional metasurface elements using existing equipment in a foundry to economically produce metasurface elements. For example, one of the design criteria traditionally used to customize the optical properties of a metasurface element is the substrate thickness. Changing this substrate thickness provides another degree of freedom for metasurface element designers to obtain the desired optical properties. However, the existing equipment in most foundries has limitations, resulting in specific mechanical requirements for the substrate on which the metasurface element is to be manufactured. For standard substrate diameters within a foundry, such as 200 mm and 300 mm, the thickness of the substrate is limited to 725 microns and 775 microns, respectively. These fixed substrate thicknesses in turn place specific requirements on the optical function of a system of metasurfaces formed on a substrate or multiple metasurfaces formed on such a substrate, and therefore the design (in mass production, for example, 5,000 metasurfaces are formed on one or more chips).

[0228] Thus, various embodiments relate to processes that adapt the manufacture of a metasurface element or system to a specific substrate thickness on which the metasurface or metasurface system is to be produced. For example, in various embodiments, the phase shift that needs to be applied by the metasurface element to impart a specific function to the entire optical element will be specific to the thickness of the substrate on which the element is formed. Thus, in some embodiments, a process for designing and manufacturing a metasurface element includes: (1) considering the device specifications of the metasurface element, (2) considering the thickness and optical properties (refractive index and absorptivity) of the substrate on which the metasurface is to be formed, (3) optimizing the phase difference profile of the metasurface to obtain the desired substrate performance specifications, and (4) determining the thickness and planar dimensions of the metasurface element required to reproduce the phase profile.

[0229] refer to Figure 3 , provides an exemplary process for producing a metasurface using a standard substrate thickness. As shown in the figure, after the deposition of the metasurface material and the photolithographic patterning and etching (as shown above Figures 1A to 1GAs described above), if the super surface layer is designed to be a standard substrate thickness, an additional protective layer or AR coating can be set on the super surface layer before sending it to further back-end processing. In a variety of such embodiments, the back-end processing can include singulating thousands of super surfaces formed on the entire substrate using a dicing process. In addition, in the embodiment where it is desired to produce a super surface with a final surface thickness different from the standard thickness discussed above, an additional step of changing the thickness of the underlying substrate can be performed. In these embodiments, the super surface will initially be formed on a substrate with a diameter of 200 mm or 300 mm in a semiconductor process with a standard substrate diameter (725 or 775 microns, respectively) and a thickness standard (725 or 775 microns, respectively), which is again consistent with industrial standards. After the super surface is initially defined on a substrate of standard thickness, subsequent back-end processing will then be performed to change the thickness of the substrate. Suitable methods for changing the thickness of the substrate according to an embodiment include, for example, grinding or a combination of grinding and chemical treatment to gradually remove the substrate material. In these embodiments, the final substrate thickness of the super surface that has been formed can be any value less than the starting standard thickness. Alternatively, if a thicker substrate is desired, then, depending on the embodiment, two separate wafers, each comprising any number of metasurfaces (1,000 to 10,000 individual metasurfaces), can be combined to achieve the desired thickness through a wafer bonding process so that the final integral unit (having a set of metasurfaces on both sides) has the total thickness desired for the final design. If the desired final thickness is 2 times the standard thickness, then processing according to such embodiments can be performed on two substrates of standard thickness, or it can be performed on two thinned substrates so that the final thickness of the combined unit has any desired thickness. In these embodiments, the "back-end processing" can include an additional wafer bonding step, where each individual substrate can be aligned with each other before being combined.

[0230] Embodiments for fabricating metasurface elements with non-ideal features

[0231] In conventional processes for designing metasurfaces, the fidelity from the designed metasurface to the fabricated shape is typically assumed to correspond 1 to 1 or to remain within a certain error range. This approach results in a metasurface framework that is typically composed of a set of shapes where one feature of the set of shapes varies, such as a circle with a varying diameter across the metasurface. However, fabrication techniques used for potential mass production of metasurfaces, such as UV lithography as described above, are typically incapable of faithfully replicating certain geometries. As such, various embodiments relate to metasurface elements and metasurface fabrication processes in which non-ideal and non-uniform shapes are used to reproduce the functionality of the metasurface.

[0232] For example, Figure 4AA cross-sectional schematic diagram of an exemplary cross section of a metasurface is provided in which a set of non-uniform shapes are distributed across the metasurface. In this particular embodiment, square pillars are desired. However, after fabrication, what is actually formed within a given metasurface is an array of squares with varying side lengths (e.g., s1) with varying radii r e Squares with rounded corners and circles with varying radii r1 or r2. Specifically, the larger features here are designed as squares or squares with rounded corners; however, when the side length of the square decreases below some minimum side length, the square becomes a circle. In a process according to an embodiment, manufacturing constraints are simulated on each desired metasurface feature shape, and then these non-ideal or non-uniform feature elements are used to determine the final metasurface element array structure.

[0233] For example, Figure 4B and 4C A diagram illustrating the printing and design pattern changes from a metasurface element mask is provided. As shown in the figure, in an embodiment for a designed square feature of 200 nm on a side and 450 nm in period, the printing manufacturing technique will actually replicate a circle of 200 nm in diameter ( Figure 4B ). In contrast, for square features with a side of 296nm and a pitch of 450nm, the fabricated features are square with rounded corners ( Figure 4C ). Thus, many embodiments of metasurface elements designed with square metasurface features can be replaced with rounded squares less than about 300 nm and circles less than about 200 nm to allow the use of industry standard CMOS replication techniques.

[0234] Embodiments for fabricating multiple metasurface elements

[0235] As previously discussed, various embodiments are directed to methods for bonding two substrate wafers incorporating metasurface elements. Such embodiments can be modified to allow for easy manufacture of multiple metasurface elements, such as doublets and triplets (e.g., metasurface elements comprising two or three separate arrays of metasurface features). In particular, although there are many wafer bonding processes, each imposes a specific thermal budget on the substrates to be connected. Since many embodiments of metasurface elements use amorphous Si as the metasurface material, overheating of the substrate can cause Si crystallization. Therefore, embodiments are proposed that allow the use of low-temperature methods to form metasurface doublets and triplets, such as using UV-cured polymers (e.g., benzocyclobutane (BCB), etc.) or plasma-activated SiO2 to allow two or more metasurface elements to be wafer bonded at low temperatures.

[0236] refer to Figure 5, showing a schematic diagram for forming a metasurface doublet according to an embodiment. As shown, in a variety of such embodiments, a plurality of unique metasurface elements (30 and 32) are fabricated on two different substrates (34 and 36). The metasurface elements are then made into a combined system by fusing the bottom of each unique substrate (e.g., a portion of the substrate surface without any metasurface element). As described above, the substrates can be melted by wafer bonding technology, optical keys, or any suitable method for combining two unique elements into a single element within the allowed thermal budget of the metasurface material used. In many embodiments, the bonding material (38) can be an adhesive, such as benzocyclobutene, a cured polymer SU8, or a silicon dioxide film that facilitates glass bonding. If 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. In addition, although not shown, it can be as Figure 2A and 2B The metasurface is embedded as described in the embodiment shown. Figure 3 As shown, the thickness of the two substrates that ultimately make up the total thickness of the space between the metasurfaces can be additionally varied to optimize certain properties of the combined system.

[0237] Although the present disclosure has so far detailed embodiments in which only two metasurface elements are combined, the process can be generalized to any number of metasurface elements. For example, some applications may require combining three or more metasurfaces into an integral unit. In this case, two substrates including separate metasurface elements can form an initial uncombined unit. Figure 6 An illustration of an exemplary embodiment of such a process is provided in . As shown, in a number of such embodiments, at least one metasurface substrate (40) is patterned with a metasurface element (42) on only one side, while the other side of the substrate may be completely unpatterned or may include a bandpass filter (44) for a specific wavelength. In these embodiments, the filter may be formed from one or more suitable materials, including, for example, alternating layers of low refractive index 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 and 50) on each side of the substrate (the second metasurface substrate may also be formed by its own intermediate bonding step, as described above with respect to Figure 5As described). The metasurface substrates (40 & 46) are then made into a combined system by fusing the bottom of each unique substrate (e.g., a surface portion of the first substrate (40) is free of any metasurface elements, while a surface portion of the second substrate (46) contains one of the two metasurface elements (48 and 50)). As described above, the substrates can be fused by wafer bonding techniques, optical keys, or any suitable method for combining two unique elements into a single element within the allowed thermal budget of the metasurface material used. In many embodiments, the bonding material can be an adhesive, such as benzocyclobutene, a cured polymer SU8, or a silicon dioxide film that facilitates glass bonding. In the case 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. The bonding material is disposed on or between the surfaces of the two substrates to be joined. In certain embodiments, the various metasurface elements can optionally be encapsulated (52 and 54), as described above. However, in many embodiments, to facilitate the bonding process, at least the metasurface elements (48) near the bare substrate surface or bandpass filter (44) in the combined triplet device are embedded in a polymer and / or solid adhesive (56).

[0238] Although the above examples of combining metasurface elements have had each metasurface element separated by a solid substrate, in some embodiments, each metasurface element may be separated by an air gap. Figure 7 , showing a schematic diagram of a metasurface bilayer including an air gap. As shown in the figure, in a plurality of such embodiments, using a suitable method, such as the above Figure 5 The described method forms two or more metasurface elements (60 and 62) on a unique substrate (64 and 66). The unique metasurface elements are then combined with a third substrate or spacer substrate (68) that includes one or more single hole units (70) etched to form a monolithic unit, and the space between the metaholes is not filled (i.e., thereby forming air gaps between the metasurface elements (60 & 62)). The space between the metasurfaces provides an additional design tool for system-level optimization. For example, in many embodiments, by adjusting the thickness of the spacer wafer, a variety of different designs can be achieved. In addition, in various embodiments, such as Figure 7 As shown, additional spacer substrates (72) may be added to incorporate other system elements, such as illuminators and / or sensors (74).

[0239] In embodiments incorporating such a spacer substrate, any suitable substrate material may be used. For example, in many embodiments, the spacer substrate may be any low refractive index material, such as a polymer, SiO2, glass, etc. Additionally, in other embodiments, the spacer material may be coated with black chrome. Metasurface elements may also be formed from any material optimized for a particular bandwidth, such as silicon, TiO2, alumina, metal, etc. Metasurface elements may also be formed using materials such as Figures 1A to 1G The method described above can be manufactured using a common semiconductor manufacturing process.

[0240] The above embodiments describe processes for combining two and three metasurfaces; however, such embodiments can be extended beyond just two or three metasurfaces. Figures 5 to 7 The described steps are iterative, and embodiments allow stacking of any number of metasurface elements. 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 these embodiments, first, an optional spacer layer (90) is formed on the sensor / illuminator (92) by an appropriate deposition process, such as, for example, referring to Figures 1A to 1G As described. After the spacer layer (90), any number of metasurface elements (80 to metasurface n+1) can be manufactured as needed to perform the desired function. Each subsequent metasurface can also be separated by a spacer layer (86 to spacer n+1), and the thickness of each spacer layer can vary according to the requirements of the optical design. As previously described, the spacer layer in these embodiments can be any low refractive index material, such as polymer, SiO2, glass. Also as previously described, the metasurface elements in these embodiments can also be any material optimized for a specific bandwidth, such as silicon, TiO2, alumina, metal, etc. The metasurface elements can generally be used Figures 1A to 1G The method shown may be used to manufacture the device or other suitable semiconductor manufacturing processes.

[0241] Although the above description assumes integration with a sensor or illuminator (92), Figure 8B As shown, a set of metasurface elements and spacer layers can also be iteratively fabricated on a substrate (90). As shown, in these embodiments, the process is as described with respect to Fig. 8A As shown, instead of integrating the metasurface / spacer stack onto the sensor / illuminator (92), the stack is produced on a separate substrate (90). The combined substrate and stack according to such an embodiment can then be integrated into an optical system or used as a standalone optical component.

[0242] Multilayer metasurface elements and implementation methods for their manufacture

[0243] Although in the previously detailed embodiments, 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), in various embodiments, multiple two layers of patterned material can be provided at a certain distance from each other at a microscopic distance (for example, the distance between each other is less than or equal to the wavelength of light) so that the layers combine to form a single metasurface element to perform a single optical function. This may be particularly advantageous when the optical function required requires very complex metasurface features. Such complex features may be beyond the manufacturing capabilities of standard CMOS manufacturing technology. In such cases, a combination of simple features arranged at microscopic distances according to the embodiments can be used to replicate the optical function of complex feature shapes. Reference Fig. 9 , a schematic diagram of an embodiment of a metasurface element is provided, the metasurface element comprising two layers of patterned material separated by a distance tfset. Although only a schematic diagram for a two-layer system is shown, it will be understood that any number of such layers may be provided, as long as the distance tfset is 偏移 Small enough to allow the combination of optical functions of multiple layers. These feature layers can be formed and combined using any suitable combination of the fabrication steps set forth with respect to FIGS. 1 to 8 . Implementation of the Metasurface Components and VCSELs

[0244] The techniques and processes for manufacturing metasurface elements according to embodiments also directly enable them to be integrated with illumination sources. Of particular interest is the combination of metasurface elements with VCSELs and VCSEL arrays. Typically, transmission-type metasurface elements can imprint arbitrary phase difference profiles on electromagnetic waves, thereby producing any radiation pattern in the far field. The manufacturing techniques for metasurface elements according to embodiments enable direct integration with VCSELs, solid-state lasers, quantum cascade lasers, LEDs, superluminescent LEDs, or any solid-state light source.

[0245] A VCSEL can be conceptualized as a single-mode (or few-mode) laser that produces a nearly collimated laser beam at a single wavelength. Typically, to produce sufficient power or spatial range, a device will not contain one VCSEL, but rather a two-dimensional array of VCSELs. The light has a distribution (or illumination) in real space and angular space. A metasurface that is properly co-designed and integrated with a VCSEL array has the ability to transform the real-space and angular-space distribution of a VCSEL or VCSEL array. In particular, pairing a metasurface element with a VCSEL can enable the metasurface element to imprint an arbitrary radiation pattern on the source (e.g., a batwing, top hat, super-Gaussian pattern, or other patterns known in the art).

[0246] Fig. 10AA flow chart of a process for manufacturing a metasurface to generate any desired far-field intensity from a VCSEL array according to an embodiment is shown. In order to obtain illumination in real space, according to an embodiment, it is assumed that the VCSEL operates in a far-field state. According to experimental data, the characteristic far field (VCSEL-FF) of the VCSEL will propagate to the surface under illumination, in this case, the metasurface element defined above. In the case of a VCSEL array, the outputs of the through-holes (VCSEL-FF) from multiple VCSELs are summed on the surface under the assumption of incoherence to generate illumination. Then, the surface illumination will give the intensity distribution of the metasurface element (I-MS). From the VCSEL far-field angular distribution, it is derived that each point on this illuminated surface also has an incident light angular distribution. In a simplified case, according to an embodiment, it can be considered that all illuminated points have the same VCSEL far-field angular distribution, although each point has a slightly different angular distribution.

[0247] To produce a metasurface element that takes into account the angular distribution at the metasurface element in the design, the target far-field distribution (target_FF) of embodiments of the method constructs a pseudo-far-field (pseudo-FF) having the properties of the convolution:

[0248] ((pseudo-FF)*(VCSEL-FF))(x,y)=(target-FF)(x,y)(EQ.1)

[0249] That is, according to embodiments, the pseudo far field convolved with the VCSEL far field reproduces the target far field. In these embodiments, the pseudo far field is calculated by fitting a curve to the target function. The (pseudo-FF) is then used as the target (or target function) in the rest of the process.

[0250] In various embodiments, the process is initialized by discretizing the metasurface mesh and setting the phase to a certain initial condition. In various embodiments, a cost function is determined. In various embodiments, this value is selected as the square error of the metasurface far-field projection when the VCSEL irradiates (pseudo-FF). In some embodiments, other goals can also be set, such as the smoothness of the calculated results in the far field. For each objective lens, a corresponding gradient function is also derived. Then, the calculation results of the gradient function and the cost function are used as inputs to the optimization algorithm according to the embodiment in the embodiment, such as in Fig. 10A According to an embodiment, the optimization algorithm updates the results of the pixel phase and continues until the objective function meets some criteria (i.e., converges). After the cost function converges, the desired metasurface phase profile is output based on the wavelength and the desired material (e.g., as described below), and the metasurface element design is selected, and a physical design can be created for the metasurface element.

[0251] Sample data plots show the output of the process of phase (10B) and intensity (10C) according to the embodiments after employing the above algorithm for an example case. As shown, in these embodiments, the phase is encoded by the metasurface element and the intensity distribution on the right is produced after the laser source passes through the metasurface element and is projected into the far field. Therefore, using such a process, it is possible to obtain predicted performance data for the proposed metasurface element under the desired operating conditions, and illustrate the method of optimizing performance by modifying various aspects of the metasurface element design, such as the size, height and spacing of the element, etc.

[0252] Embodiments of introducing metasurface elements into lighting arrays

[0253] Although the above processes focus on integrating metasurface elements with a single illumination source, e.g. Figure 7 and 8A As shown, metasurface elements can also be integrated with a set of pixelated and distributed light sources. Fig.11 As shown, various embodiments may include a set of illumination sources p1, p2, ... p n (Although shown in 1D, it should be understood that the system can be extended to a 2D array and that the array generally need not be periodically spaced) to illuminate a scene (110). Although each illuminator can be identical, 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. In certain applications, Fig.11 The array in can be an array of VCSELs. In other applications, there can be three colors (e.g., red, green, and blue), which are then repeated periodically within the array. Because each illuminator comprising the array can have unique characteristics, it is also advantageous to have an array of metasurface elements each having uniquely designed characteristics. In these embodiments, the metasurface array (100) can be separated by a spacer layer (104) (with Figure 7 or 8B similar) offset from the illuminator array (102). As previously described, the thickness of the spacer layer (104) will depend on the specific design, but in many embodiments, the thickness is configured to allow light from the illumination source to be fully diverged before interacting with the metasurface array (100). Again, the function of each metasurface element in the array can generally be unique, but in certain embodiments, each metasurface element can provide collimation of the underlying illuminator pixel, or each metasurface element can be used to further mix each underlying illuminator pixel.

[0254] In addition to the first metasurface array (100), various embodiments may introduce a second metasurface element (106) to further shape the light emitted from the illuminator array (102). In various embodiments, the second metasurface element (106) is also offset by a second spacer layer (108). Although the second spacer layer (108) is Fig.11 , but it should be understood that the spacer layer can also be a solid material, as in the other embodiments described above. In various embodiments, the first metasurface array (100) is configured to introduce additional angular divergence in the illuminator array (102), while the second metasurface element (106) imprints a specific far-field radiation pattern onto the light field. In other embodiments, the second metasurface element (106) can also be formed by an array of metasurface elements each having a unique function. In all such embodiments, the Fig. 10A The embodiments of the algorithm described in the invention are used to design the metasurface elements in the system, in particular the second metasurface element. Although in this specific case, the system has been described as an array of pixelated illuminators (102) shaped by the metasurface array / element to illuminate the scene (110); however, this is not repeated here. The system can also be considered in reverse. For example, the pixelated illumination source can instead be the pixels of a CMOS image sensor, and instead of light being projected onto the scene, the system can be configured to collect light from the scene (110) and focus the light down to the pixels.

[0255] In all embodiments where the illumination source is a VCSEL, it will be appreciated that the present disclosure may also be applied to arrays of VCSELs (VCSEL arrays). In such a VCSEL array, many individual aperture VCSELs with designable properties are combined on a single chip. Such VCSEL arrays are used to increase the total output power of the illumination source. The array may consist of a one-dimensional row of individual VCSELs or a 2D grid of individual VCSELs, wherein in each case the specific properties of the VCSELs (e.g., power, wavelength, aperture, beam divergence, etc.) as well as the arrangement of the individual VCSELs (e.g., center-to-center distance, periodic or aperiodic spacing, etc.) may be freely selected.

[0256] In the context of metasurface element integration, embodiments of metasurface elements having typically (but not necessarily) uniquely designed properties may be patterned on top of each individual VCSEL in an array using any of the techniques outlined herein. For example, a metasurface may be fabricated directly on the end face of each individual VCSEL in an array, or a suitable dielectric spacer may be deposited on the VCSEL and then the metasurface integrated on top of the combined dielectric layer and VCSEL. In these embodiments, the metasurface may provide a specific radiation pattern for each VCSEL, and the entire system (VCSEL properties, geometric parameters, and metasurface-enabled radiation pattern) may be iteratively optimized for a specific set of performance parameters.

[0257] In various other embodiments, a dielectric material having a lower refractive index than the constituent VCSEL material may be deposited and planarized such that a single metasurface may be patterned on top of the dielectric material. This is in contrast to embodiments where each VCSEL in the array has a unique metasurface patterned on its facet. Again, in these embodiments, the combined system may be optimized to achieve the desired performance. Finally, in all of the above embodiments, wafer-level optical processes may be used to achieve integration of the metasurface with the VCSEL array. In these embodiments, similar to Figure 7 In the device shown, the spacer layer can be air rather than a solid dielectric.

[0258] Implementation of Metasurface Elements into 3D Applications

[0259] In some 3D structured lighting applications, a pseudo-random binary array (PSBA) is projected onto the scene. A typical PSBA is constructed by discretizing the 2D space (for example, in a square grid). Each grid point in the xy 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 grid point has a dot (representing a binary value of 1) or does not have a dot (representing a binary value of 0).

[0260] Typically, a diffractive optical element (DOE) is used to convert incident laser light (e.g., from a VCSEL or VCSEL array) into a single point pattern. Such a conversion scheme relies only on two intensity values ​​(point or no point) in the projected field. However, it is often desirable to assign multiple patterns to a single scene and have each of the multiple patterns exist on a separable information channel (i.e., having two patterns projected onto the scene from a single element and having a method to uniquely identify each pattern on the sensor plane). In some 3D imaging schemes, multiple patterns are projected onto the scene in different time slices (time variations). These schemes use multiple different illumination patterns or certain active elements (e.g., spatial light modulators) that can be electrostatically tuned to change the projected pattern at different points in time. However, these schemes do not allow single-shot acquisition, increase complexity and therefore increase system cost, and are often much larger than integrated lasers / DOEs. Therefore, various embodiments relate to metasurface elements that are configured to provide single-shot acquisition for 3D structured light applications.

[0261] refer to Figures 12A to 12C , an exemplary embodiment of a metasurface element (120) composed of a plurality of metasurface features (122) having an asymmetric cross-section (e.g., rectangular or elliptical), a fixed height, and a rotation axis provides a "spot" pattern capable of imprinting two unique dot patterns with two orthogonal polarizations onto an illumination source (124). Although this exemplary embodiment will be discussed with reference to a laser with a fixed polarization, the embodiment can also be configured to operate on an unpolarized source (e.g., a light emitting diode (LED)), where the function of the metasurface element is to separate the unpolarized light into two different polarizations (e.g., Fig. 12B ), and imprint any desired arbitrary pattern onto the projected light. According to the embodiments described in the present disclosure, regardless of the illumination source, in various embodiments, the metasurface element can be integrated with the illumination source (e.g., LED, VCSEL, VCSEL array, etc.). For example, referring to Fig. 12A As shown, the metasurface element (120) can be fabricated on a substrate (126) of a desired thickness, which can then be bonded using a spacer layer that is subsequently bonded to an illumination source (124), bonded directly to the illumination source, or bonded to the substrate on which the metasurface element is formed, which can then be cut into individual units and combined with a laser source via back-end packaging. For various embodiments of the 3D imaging system, the illumination source can be in the near infrared (NIR) (e.g., at a wavelength of 850 or 940 nm).

[0262] Regardless of the specific configuration and fabrication of the metasurface element used, in these embodiments, the metasurface element works not only by shaping the intensity, but also by shaping the polarization of the light emitted by the illumination source. Specifically, in addition to intensity variations, light also has a vector quantity called polarization. Given a polarized illumination source, the illumination polarization can be decomposed into two orthogonal polarization or channel bases. Due to the orthogonality of these polarization bases, any pattern printed on these different polarization channels can also be independently sensed by a suitable detector configured to separate these polarization channels.

[0263] As a concrete example, consider the following situation. For an illumination source (in this case, a polarized illumination source such as a laser) that emits horizontally polarized light |H>, the output can be decomposed into two polarizations according to the following formula:

[0264]

[0265] Where |A> and |D> are diagonal and anti-diagonal polarizations in this example (although it will be appreciated that any set of polarizations may be used depending on the embodiment). Fig. 12C As shown, the pattern of the metasurface features (122) of the metasurface element (120) disposed on the illumination source (124) is configured so that it will separate the dot patterns (such as Fig. 12B According to an embodiment, for clarity, these dot patterns may be unique for each polarization, such as Fig. 12B As shown in the exemplary schematic diagram of , or they may partially overlap. However, regardless of the specific configuration of the points, in an embodiment, these patterns are projected onto the same spatial area (i.e., their grids have the same spatial origin). In various embodiments, complementary dot patterns can be used so that for each point where there is a dot in dot matrix 1, there is no dot in dot matrix 2, and vice versa, but this is not necessary. Such a complementary dot pattern configuration has the following advantages: if a single point (e.g., an area) of the scene is lost during capture, there are complementary points with separate polarizations that can capture it, thereby providing a certain redundancy. In addition, although two patterns of points on a square grid are described with respect to this particular exemplary embodiment, it should be understood that the projected pattern can be any configuration having any suitable geometry and shape. Similarly, although specific illumination polarizations and the number of polarizations on which the illumination polarization is decomposed have been described, it should be understood that any polarization and any number of different polarizations can be used depending on the embodiment.

[0266] As described above, embodiments operate due to the orthogonality of the polarization channels on which each pattern is printed. Due to this orthogonality, the reflected light from a given scene can be separated using a suitable detector to create multiple images of the same scene, one image with polarization 1 corresponding to pattern 1 and one with polarization 2 corresponding to pattern 2, such as Fig. 12B As shown. The end result is that embodiments of such a system provide two nominally independent measurements of the distortion pattern reflected from the scene without the need for time multiplexing. Thus, embodiments of such a system can be used to provide single-shot, multiple-shot measurements in a 3D imaging system, thereby reducing ambiguity and improving accuracy.

[0267] For example, typical pattern projection systems used in mobile devices have a limit on the total number of points they can project onto a scene. This limitation is due to a combination of the number of constituent VCSELs in a VCSEL array (which cannot be changed by any manipulation of the optics that generate the pattern) and the ability of the optics that generate the structured light pattern to create multiple copies of each VCSEL of the VCSEL array. In practical implementations, this limits the number of projected points in the pattern to a specific number N (typically around 30,000). According to the above-described polarization-dependent metasurface system embodiments, due to the ability of a single metasurface element to create multiple completely unique patterns for each orthogonal polarization, even within the above-described limit, the total number of points in a given pattern can be doubled (e.g., 2N), so that in a typical system the number of points in a single projected pattern can be up to 60,000 points. This doubling can be understood by examining the properties of the pattern. Conceptually, a typical projected pattern has a set of grid points separated by some period p. At a certain distance from the projector, the pattern spans a field of view given by vertical and horizontal distances H and Y. For a conventional projector, at most 30,000 grid points will fill this field of view, making the integral In an embodiment of a metasurface polarization based solution, the optics projects one pattern with period p, and a second pattern also with period p but with a linear offset of p+p / 2, so that a new grid point is projected every half period. The end result is that within the same field of view H and Y, the density of grid points can be doubled using a metasurface enabled 3D system, depending on the embodiment.

[0268] Finally, since two unique and distinguishable patterns can be generated from the system according to embodiments, such systems can also be optimized for short-range (<1m) and long-range (>1m) 3D imaging. For example, certain patterns can be configured to distinguish objects at a short distance from the device, while different patterns can be configured to distinguish objects at a longer distance from the device. In these embodiments, a single device can be used to create, for example, pattern 1 with polarization 1 for short-range measurements and pattern 2 with polarization 2 for long-range measurements in a single pass.

[0269] Embodiments of introducing metasurface elements into imaging systems

[0270] In some embodiments, using Figure 7 The methods described in and 8 to integrate multiple metasurface elements (e.g., two or more) allow the combined system to achieve the functions required for practical CMOS camera imaging. Specifically, CMOS cameras (e.g., cameras used in mobile phones, computers, tablets, etc., for collecting visible light scenes or infrared images for biometric identification) require imaging systems with an increased field of view (FOV), independent control of the chief ray angle (CRA) as a function of the FOV height of the CMOS image sensor, and minimal optical distortion of the scene to be imaged. These terms will be understood to have the conventional meanings of those skilled in the art. For a conventional imaging system composed of refractive lenses, up to five or six unique lenses must be combined to perform this function. Moreover, implementing a metasurface element in such an imaging system does not provide enough degrees of freedom to fully control these parameters (CRA, FOV, and minimized distortion). However, according to an embodiment, by combining multiple metasurfaces, each with a unique and independent phase difference profile, an imaging system with a wide FOV, controllable distortion, and controllable CRA can be achieved.

[0271] refer to Fig.13 , provides a ray tracing diagram of an exemplary implementation of a system having two metasurface elements (130 and 132) bonded on a single substrate (134) according to an embodiment. 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 here, it should be understood that these metasurface elements can be made using the methods described in any of the previous figures and can be made using methods such as Figure 5. In many such embodiments, the metasurface element can be formed by 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 have been configured so that they can be combined to form a good image over a wide FOV (±44 degrees in this example), but it should be understood that this is not a limiting case). As shown in the figure, it is surprisingly found that an embodiment of this two-metasurface system naturally produces focused rays at the filter plane and the image plane telecentrically (i.e., with 0 degree CRA). In short, although traditional refractive designs require complex multi-element systems to achieve such telecentric designs, according to embodiments, only two metasurface elements are required to achieve similar telecentric designs. This telecentricity in turn leads to improved optical performance. In particular, low (e.g., zero or near zero degree CRA) allows the bandwidth of an optical filter (136) for narrowband applications to be narrowed. In traditional refractive designs, especially for compact mobile applications, the CRA is typically about 15 to 30 degrees. These larger CRAs, in turn, require a significant increase in the filter bandwidth to allow more ambient light to enter the detector. In narrow-band applications (e.g., near-IR VCSEL arrays), this ambient light can be a constant source of noise. Therefore, Fig.13 Implementation of embodiments of the combined metasurface / filter system shown in would allow for better ambient light performance.

[0272] An additional attribute of an embodiment of this telecentric design is that the metasurface system provides more uniform illumination at the image sensor (referred to as "relative illumination" by those skilled in the art). Embodiments of the metasurface system also provide additional design variations relative to traditional refractive lens systems. A typical CMOS image sensor (CIS) requires a microlens to be associated with each pixel. Due to the large variation in CRA over a given sensor plane, which is inherent to refractive optical systems, the microlens array on the CIS also requires complex CRA specifications. However, in an embodiment of the metasurface system described herein, the CRA of the microlens array can be configured to be a constant 0 degrees across the CIS, allowing for greater simplicity in the design and manufacture of the microlens array. Alternatively, in some embodiments, the microlens array can be completely removed from the CIS, saving process steps in the production of the CIS.

[0273] Although embodiments of metasurface systems for CMOS sensors have been shown thus far to have two metasurface elements on opposite sides of a single substrate, in various other embodiments, the two metasurface elements may be disposed on separate substrates. Exemplary embodiments of such systems are described in detail in the accompanying drawings. Fig.14As shown in the figure, in many such embodiments, the metasurface elements are disposed on two separate substrates (138 and 140) and an air gap (142) is disposed between the two elements. One advantage of such embodiments incorporating an air gap is that in air, light can be bent further over a shorter distance d than in a glass substrate, thereby allowing for a greater widening of the illumination range while the spacing between the metasurface elements is shorter, thereby allowing for a reduction in the overall size of the metasurface optical system. Fig.14 As shown, in various embodiments, the metasurface elements are disposed on the surfaces of the substrates (138 and 140) that face the air gap (142). Such implementations allow the metasurface elements to be protected from environmental contamination. Additionally, such embodiments allow the outer surface of the imager-side substrate (140) to remain pattern-free, thereby allowing the optical filter (144) to be integrated directly on the substrate. Although in Fig.14 In the illustrated embodiment, the metasurface elements are arranged to face inwardly with respect to the air gap between them, but it will be appreciated that they may be arranged on either surface of the two substrates. Fig.15 The production of the metasurface system shown in is implemented. Fig.15 The generation of the metasurface system shown in can follow the above process, for example with Figure 7 Related process.

[0274] Although the above discussion has described a metasurface system configured to provide telecentric optical properties, in some cases (e.g., where distortion correction is desired), it is necessary to introduce a non-zero CRA. Accordingly, embodiments are also directed to a metasurface system comprising at least three metasurfaces capable of simultaneously controlling FOV, distortion, and CRA. Fig.15 A ray tracing diagram of an exemplary embodiment of a metasurface system including three metasurface elements with unique phase profiles is shown in . The introduction of additional metasurface elements or each element allows for a separate, arbitrary phase difference profile to be achieved, providing greater freedom to control the path of light compared to a typical system consisting of an equivalent number of refractive elements. For example, according to an embodiment, to replicate the optical functionality of a system consisting of three metasurfaces, 6-7 refractive optical elements may be required in a conventional system. In this way, 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.

[0275] Go to Fig.15As shown in the metasurface system itself, such an imaging system may include three or more metasurface elements (150, 152, and 154) arranged on two or more substrates (156 and 158). As previously described, these metasurface elements can be composed of any suitable dielectric material, especially those with minimal absorption at the wavelength of interest. As shown, in various embodiments, the first two metasurface elements (150 and 152) can impart telecentric optical properties on the incident light, while the third metasurface element (154) (e.g., closest to the filter (156) and the imager) can further spread or bend the light, thereby applying a non-zero CRA to the light striking the imager. Although in Fig.15 A specific arrangement of the metasurface elements and substrate is shown in the illustrated system, but such a figure is intended to be used as an example and does not limit the current disclosure to this exact system response. Regardless of the specific arrangement of the elements, the fabrication of such a metasurface element can follow the process described above, for example with respect to Figure 6 Process shown and described.

[0276] Using this three-metasurface element system according to an embodiment, the CRA can be controlled to minimize grid distortion in a CMOS image sensor. For example, Fig.16 A data graph is provided showing the Fig.15 The final control of the CRA at the CMOS image sensor of the imaging system of the embodiment shown is a function of the field height. This is an exemplary case, and the CRA control as a function of the field height can take other functional forms instead of the linear case shown below. Similarly, Fig.17 Provides a Fig.15 Grid distortion diagram of the imaging system of the illustrated embodiment. As shown, the embodiment of this imaging system allows minimizing the grid distortion to less than 5% over the entire FOV of the imaging system.

[0277] Embodiments of introducing metasurface elements into imaging / sensing systems

[0278] In view of the described advantages of using metasurface elements according to embodiments on sensing optics and projection optics, various embodiments are directed to metasurface systems configured for use in combined illumination-sensing modules. Fig.18, providing a schematic diagram of an integrated illuminator and sensor system according to an embodiment. As shown, in these embodiments, the illuminator (160) has a plurality of spacers (162 and 162') and a metasurface element (164 and 164'), alone or in combination with a refractive element configured with a refractive element to provide a specific radiation pattern for illuminating certain objects or scenes (166). A sensor (168) (e.g., a CMOS image sensor) having a corresponding metasurface system is used to detect radiation or detect radiation from an image of a scene. In these embodiments, the entire system - metasurface elements (162 and 162'), sensors (168), illuminators (160) - can be configured to operate over certain specific bandwidths or at specific wavelengths of interest, and can be combined onto a single platform (170). The illuminator and sensor metasurface elements (162 and 162') can be configured to perform any polarization of the electric field. Embodiments of this combined system can be used on computers, mobile phones, television monitors, wall-mounted units, credit cards, tablet computers, mirrors, etc.

[0279] As mentioned above about Figures 12A to 12C As discussed, the metasurface also allows unique functionalities to be imprinted on two orthogonal polarizations. Therefore, polarization can also be used as an additional optimization variable to co-design various embodiments of the metasurface illuminator-sensing system. Fig.19 , providing a schematic diagram of an integrated illuminator system that also acts on the polarization of the radiation field. As shown, in one such exemplary embodiment, the illuminator (172) carries one or more metasurface elements (174 and 174') and suitable spacers (176 and 176'), and optional refractive elements for illuminating a scene or object (178). In these embodiments, the metasurface elements are designed so that for any two orthogonal polarizations of light, two unique and independent radiation patterns can be generated. A sensor (180) having a corresponding set of metasurface elements is used to collect light reflected from the scene. As shown, the illuminator and sensor metasurface elements have been configured to work together so that the two orthogonal polarizations used to generate the radiation pattern form two unique images on the sensor. According to the system of the embodiment - metasurface (174 and 174'), sensor (180), illuminator (172) - can be optimized for operation over certain bandwidths or at specific wavelengths of interest, and can be combined onto a single platform (182). It will be understood that the illuminator and sensor metasurface elements according to the embodiment can be configured to perform any polarization of the electric field. Combination systems according to embodiments may be used on computers, cell phones, television monitors, wall mounted units, credit cards, tablet computers, mirrors, and the like.

[0280] Implementation scheme of metasurface element material system

[0281] As previously discussed, each individual metasurface element in any optical system, whether it is one or more metasurface elements that make up the system, has some specific 2D phase and transmission function φ(x, y) and t(x, y) that is performed. Although each metasurface element can generally have a unique phase and transmittance distribution, the nanostructure features that contain any metasurface element embedded in the same material, with the same basic composition and a specific wavelength are the same. In most practical single-wavelength applications, it is desirable to achieve maximum transmittance (close to 1) and maintain uniformity on the metasurface, while the phase only needs to take values ​​between 0 and 2π. In summary, for some wavelength of interest, material system (metasurface material and embedding material), fixed thickness and element spacing, it is only necessary to find a set of in-plane dimensions containing nanostructure features so that the phase delay from 0 to 2π can be imprinted on the incident light field. Therefore, for various embodiments of metasurface element design under fixed material and wavelength conditions, the only variable from design to design is the distribution of those nanostructure features on the metasurface element. Therefore, various embodiments of metasurface element material conditions suitable for performing specific optical functions over a desired wavelength range are described. Although the following discussion sets forth embodiments of metasurface elements and systems, and processes for making such metasurface elements and systems, it will be understood that the following embodiments are provided for exemplary purposes only and are not meant to be limiting.

[0282] refer to Fig. 20 , providing phase and transmission diagrams of an embodiment of a metasurface element including a silicon column embedded in SiO2. The upper left figure provides a heat map of transmission, which is a function of column diameter and height and a color scale, as shown in the right figure. The upper right figure provides a phase diagram as a function of column diameter and height. The lower left provides a functional relationship diagram of transmission line scan and column diameter when the height is fixed to 600nm. The lower right corner provides a line scan diagram of relative phase, which is a function of column diameter when the height is fixed to 600nm. It will be understood that, according to the embodiment, using these figures, a specific set column diameter and height for a specific transmittance and phase can be determined for all suitable wavelengths, as well as a specific diameter for a height of 600nm. In various embodiments, the column height can vary between 500 and 1000nm, and the column diameter can vary between 100 and 300nm. In various other embodiments, the column diameter can vary between 100 and 200nm, and the column height can vary between 500 and 800nm. In various other embodiments, at a pillar height of 600 nm, the pillar diameter may vary between 100 and 300 nm. The particular height and diameter represent a local optimum for the transmission of the element, but other pillar heights may be used in embodiments as desired for the design of a particular optical system.

[0283] refer to Fig.21, providing phase and transmission diagrams of an embodiment of a metasurface element including a silicon column in air. The upper left figure provides a heat map of transmission, which is a function of the column diameter and height and the color scale, as shown in the right figure. The upper right figure provides a phase diagram as a function of the column diameter and height. The lower left corner provides a line scan of the transmittance at a fixed height of 480nm as a function of the column diameter. For a fixed height of 480nm, the lower right corner provides a line scan of the relative phase as a function of the column diameter. It will be understood that, according to the embodiment, using these figures, a specific set column diameter and height for a specific transmittance and phase can be determined for all suitable wavelengths, and a specific diameter can be determined for a height of 480nm. In various embodiments, the column height can vary between 1 and 500nm, and the column diameter can vary between 100 and 350nm. In various other embodiments, the column diameter can vary between 100 and 250nm, and the column height can vary between 150 and 500nm. In various other embodiments, at a pillar height of 480 nm, the pillar diameter may vary between 100 and 280 nm. The particular height and diameter represent a local optimum for the transmission of the element, but other pillar heights may be used in embodiments as desired for the design of a particular optical system.

[0284] Reference Fig. 22 , phase diagrams and transmission diagrams of embodiments of metasurface elements including TiO2 columns in air are provided. The upper left figure provides a heat map of transmission, which is a function of column diameter and height and color scale, as shown in the right figure. The upper right figure provides a phase diagram as a function of column diameter and height. The lower left figure provides a line scan of transmittance at a fixed height of 975nm as a function of column diameter. For a fixed height of 975nm, the lower right corner provides a line scan of relative phase as a function of column diameter. It will be understood that, according to embodiments, using these figures, a specific set column diameter and height for a specific transmittance and phase across all suitable wavelengths, as well as a specific diameter for a height of 975nm can be determined. In various embodiments, the column height can vary between 300 and 1000nm, and the column diameter can vary between 100 and 350nm. In various other embodiments, the column diameter can vary between 100 and 300nm, and the column height can vary between 300 and 400nm and / or 700 and 1000nm. In various other embodiments, at a pillar height of 975 nm, the pillar diameter may vary between 100 and 300 nm. The particular height and diameter represent a local optimum for the transmission of the element, but other pillar heights may be used in embodiments as desired for the design of a particular optical system.

[0285] Reference Fig.23, phase diagrams and transmission diagrams of embodiments of metasurface elements including amorphous silicon pillars embedded in benzocyclobutane (BCB) polymers are provided. The top diagram provides a scan of the transmission line as a function of the pillar diameter at a fixed height of 590nm and an element period of 400nm. The bottom diagram provides a line scan of the phase as a function of the pillar diameter at a fixed height of 590nm and an element period of 400nm. It will be understood that, according to embodiments, using these diagrams, the pillar diameter and height for a specific setting of a specific transmission and phase across all suitable wavelengths, as well as a specific diameter for a height of 590nm can be determined. In various embodiments, at a pillar height of 975nm, the pillar diameter may vary between 100 and 300nm. In various other embodiments, the pillar diameter made is between 100 and 225nm. The specific height represents a local optimum for element transmission, but other pillar heights may be used according to the design requirements of a specific optical system.

[0286] Reference Fig.24 , phase and transmission plots of an embodiment of a metamaterial element comprising amorphous silicon pillars embedded in silicon dioxide are provided. The top plot provides a scan of the transmission line as a function of the pillar diameter at a fixed height of 600nm and an element period of 350nm. The bottom plot provides a line scan of the phase as a function of the pillar diameter at a fixed height of 600nm and an element period of 350nm. It will be appreciated that, according to embodiments, using these plots, a specific set pillar diameter and height for a specific transmittance and phase, as well as a specific diameter for a height of 600nm, can be determined for all suitable wavelengths. In various embodiments, at a pillar height of 600nm, the pillar diameter may vary between 100 and 275nm. In various other embodiments, the pillar diameter varies from 100 to 175nm. The specific height represents a local optimum for element transmission, but other pillar heights may be used depending on the design requirements of a particular optical system.

[0287] In other embodiments, amorphous-Si metasurface features embedded in SU8 were also tested and found to be suitable with a column height of 675nm and a column diameter of 100-300nm. In addition, according to various embodiments, amorphous-Si metasurface features in air with a column height of 600nm and a column diameter of 100-300nm and an element spacing of 450nm may be suitable.

[0288] Although specific combinations of metamaterials and embedded materials are described above, it will be appreciated that similar maps of metasurface features, transmittance, and phase may be produced in accordance with embodiments of the present invention.

[0289] Doctrine of Equivalence

[0290] Therefore, although the present invention has been described in certain specific aspects, many other modifications and variations will be apparent to those skilled in the art. Therefore, it should be understood that the present invention may be practiced in a manner different from that specifically described. Therefore, the embodiments of the present invention should be considered in all aspects to be illustrative and not restrictive.

Claims

1. A metasurface-enabled illumination or sensor array comprising: at least one illumination source or sensor element; a plurality of metasurface elements arranged in a planar array such that light emitted from the at least one illumination source or light incident on each of the at least one sensor element passes through the planar array of metasurface elements; Wherein, the plurality of metasurface elements are configured asymmetrically such that the metasurface elements are configured to imprint at least one of at least two far-field functions from the at least one illumination source or guide light from incident light into at least one of the at least two far-field functions based on light passing through the metasurface elements prior to illumination of the sensor element.

2. A metasurface-enabled lighting or sensor array according to claim 1, wherein the asymmetry is a result of different spacings of the metasurface elements along two orthogonal directions.

3. The metasurface-enabled illumination or sensor array of claim 1, wherein: The at least two far-field functions have different polarizations.

4. The metasurface-enabled illumination or sensor array of claim 1, wherein: The at least two far-field functions are linearly offset.

5. The metasurface-enabled illumination or sensor array of claim 1, wherein: A first spacer layer is disposed above the at least one illumination source and is configured to produce divergence in light emitted from the at least one illumination source or convergence in light incident on the at least one sensor element, and wherein the plurality of metasurface elements are disposed above the first spacer layer.

6. The metasurface-enabled illumination or sensor array of claim 5, further comprising: Disposing a plurality of second metasurface elements at a distance from the plurality of first metasurface elements, the plurality of second metasurface elements being configured to imprint another far-field function on a light field incident thereon; and A second spacer layer is provided between the first metasurface element and the second metasurface element so as to form an offset distance therebetween.

7. The metasurface-enabled illumination or sensor array of claim 1, further comprising: at least one refractive lens separated from the plurality of first metasurface elements, the refractive lens configured to collimate the illumination source; and A second spacer layer is provided between the metasurface element and the refractive element so as to form an offset distance therebetween.

8. The metasurface-enabled illumination or sensor array of claim 1, wherein: The at least one illumination source or sensor element comprises a plurality of identical or unique illumination sources or sensor elements arranged in a planar array; and Wherein, in an array of light emitted from each of the plurality of illumination sources or light incident on each of the plurality of sensor elements, at least one of the plurality of metasurface elements is associated with each of the plurality of illumination sources or sensor elements.

9. The metasurface-enabled illumination or sensor array of claim 1, wherein: The plurality of metasurface features on each of the metasurface elements are non-uniform and deviate from an ideal shape by a predeterminable amount based on the size of the metasurface features.

10. The metasurface-enabled illumination or sensor array of claim 1, wherein the at least one illumination source is 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.

11. The metasurface-enabled lighting or sensor array of claim 1 , wherein the at least two far-field functions are unique.

12. The metasurface-enabled lighting or sensor array of claim 1, wherein the at least two far-field functions impose at least one dot pattern on the incident light.

13. The metasurface-enabled illumination or sensor array of claim 12, wherein the at least one dot pattern has up to 60,000 binding sites.

14. The metasurface-enabled lighting or sensor array of claim 12, wherein at least two patterns are applied to the incident light.

15. A metasurface-enabled illumination or sensor array according to claim 14, wherein at least a first dot pattern is configured to acquire a measure of a foreground of a scene, and wherein at least a second dot pattern is configured to acquire a measure of a background of a scene.

16. The metasurface-enabled illumination or sensor array of claim 14, wherein at least two of the dot patterns are diagonally polarized relative to each other.

17. The metasurface-enabled illumination or sensor array of claim 12, wherein more than two dot patterns with more than two different polarizations are applied.

18. The metasurface-enabled illumination or sensor array of claim 14, wherein: The pattern is configured to be projected onto two different optical planes.

19. A single-platform imaging / sensing system enabled with a metasurface element, comprising: at least one sensor element and at least one illumination source; at least one illumination metasurface element and at least one sensor metasurface element, the at least one sensor metasurface element being disposed at an offset distance from the at least one illumination metasurface, wherein the at least one sensor metasurface element is disposed above the at least one sensor element and the at least one illumination metasurface is disposed above the at least one illumination source, and wherein the at least one illumination metasurface element and the at least one sensor metasurface element each have an associated at least one spacer layer; wherein each of the metasurface elements comprises an array of metasurface features disposed atop a substrate that is transparent to light over a specified operating bandwidth, the array of metasurface features having a feature size that is smaller than a wavelength of light within the specified operating bandwidth, and wherein at least one illumination metasurface element disposed in association with the illumination source is configured to impose a radiation pattern on a light field emitted therefrom within a plane of a plurality of metasurface features, and wherein at least one sensor metasurface element disposed in association with the at least one sensor element is configured to receive the radiation pattern of the light field after scene illumination; and wherein the at least one illumination metasurface element associated with the illumination source imprints at least one of two far-field functions on the light field based on light emitted from the at least one illumination source, and wherein the at least one sensor metasurface element associated with the sensor element directs the received light into at least one of the at least two far-field functions based on the received light.

20. The metasurface-enabled illumination or sensor array of claim 17, wherein the at least two far-field functions produce at least two patterns having orthogonal polarizations and linearly offset from each other in the light field of an illuminated scene, enabling collection of three-dimensional information about the scene.

21. The metasurface-enabled lighting or sensor array of claim 1, wherein the asymmetry is a result of an asymmetric cross-section of the plurality of metasurface elements.

22. A metasurface-enabled lighting or sensor array according to claim 21, wherein the asymmetry is a further result of at least two different rotation angles of the metasurface elements.

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