Nonplanar metasurfaces and related fabrication methods

Abstract

Methods are described for transferring optically active features, such as meta-atoms and diffractive elements formed on a planar surface, to a non-planar surface with high precision. The described methods can be used to fabricate optical devices having meta-atoms or other diffractive features disposed on non-planar surfaces and / or planar surfaces. Related optical systems and components are described.

Description

[Background technology]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority under 35 U.S.C. § 119(e) to U.S. Application No. 63 / 387,582, filed December 15, 2022, and entitled "Curved, Conformal, and Hybrid Metasurfaces and Related Fabrication Methods," which is incorporated herein by reference in its entirety.

[0002] Government Rights Statement This invention was made with government support under HR0011-22-9-0005 awarded by the Defense Advanced Research Projects Agency (DARPA). The government has certain rights in this invention.

[0003] Optical metasurfaces, alternatively known as subwavelength diffractive optical elements, are artificial media with a 2-D array of subwavelength optical structures (commonly called metaatoms). Metasurfaces are typically fabricated on planar substrates. Several techniques have previously been explored for the fabrication of curved metasurfaces. These include soft lithography, which can be used to directly pattern metaatoms onto curved surfaces, and pattern transfer from rigid to flexible substrates. However, neither method is scalable or offers sufficient fabrication precision for practical manufacturing. Summary of the Invention

[0004] The present technology relates to optics and optical systems, particularly metasurface optics and methods for fabricating metasurfaces on nonplanar surfaces. Optical systems based on nonplanar metasurfaces are also described. Such optical systems include hybrid metasurface optical systems, which comprise a metasurface conformally integrated with another optical element having a planar or nonplanar surface, and which may or may not include a stack of other optical materials. Using the described methods, large-area metasurfaces with nonplanar form factors can be fabricated. The described concepts are more generally applicable to the field of thin optics. Thin optical elements include, but are not limited to, subwavelength optics, metasurfaces, thin optical and meta-optical films described below, metamaterials, diffractive optical elements (DOEs), holographic optical elements (HOEs), thin gradient-index (GRIN) optical elements, wafer-level optics (WLOs), micro-optical elements, and the like. Thin optical elements typically comprise patterned micro- and / or nanometer-scale features disposed on a substrate to provide at least one optical function (e.g., focusing, patterning, collimating, filtering, etc.) to light incident on the thin optical element. Thin optical elements can have a maximum thickness of 10,000 times the wavelength or less, or in some cases, 1,000 times the wavelength of light at which they are designed to operate. In some cases, thin optical elements can have a maximum thickness of 10 mm or less, or in some cases, 1 mm or less. The described techniques can be useful for a variety of optical applications, including imaging, sensing, endoscopy, near-eye displays, eye tracking, and more. For example, the ability to form nonplanar metasurfaces on curved surfaces and / or multilayer material stacks provides additional degrees of freedom for designing optical systems that include metasurfaces. Furthermore, nonplanar metasurfaces enable optical functionality to be realized on components whose geometry is dictated by non-optical requirements, such as aerodynamic or ergonomic factors.

[0005] Some embodiments relate to methods for forming thin optical elements (e.g., metasurfaces) on non-planar surfaces. Such methods may include forming a thin optical element on a planar surface of a first substrate, the thin optical element comprising a plurality of patterned features disposed on the planar surface, the thin optical element providing at least one optical function to light incident on the thin optical element and having at least one particular wavelength for the at least one optical function, the plurality of patterned features including one or both of microscale features and nanometer-scale features; encapsulating a plurality of surfaces of each feature of the plurality of features on the planar surface with a thermoplastic material; peeling the thermoplastic material encapsulating the plurality of patterned features from the planar surface to form a thin optical film; and applying the thin optical film to the non-planar surface of a second substrate.

[0006] Some embodiments relate to an optical device comprising: an optically transparent substrate having a first surface and a second surface for transmitting light through the optically transparent substrate when the light is incident on the optically transparent substrate; and a thin optical film adhered to the first surface of the optically transparent substrate. The thin optical film can include a thermoplastic material encapsulating multiple surfaces of each of a plurality of patterned features, the multiple patterned features being disposed within the thermoplastic material to provide at least one optical function to light incident on the thin optical film, the multiple patterned features having at least one specific wavelength for the at least one optical function, and the multiple patterned features including one or both of microscale features and nanometer-scale features.

[0007] Some embodiments relate to hybrid meta-optical systems comprising at least one planar or non-planar metasurface and at least one planar or non-planar optical surface (e.g., a refractive, reflective, and / or diffractive optical surface) that perform at least one optical function on radiation interacting with the hybrid meta-optical system.

[0008] All combinations of the foregoing concepts and additional concepts discussed in more detail below (provided such concepts are not mutually inconsistent) are contemplated as part of the inventive subject matter disclosed herein. In particular, all combinations of claimed subject matter, as set forth at the end of this disclosure, are contemplated as part of the inventive subject matter disclosed herein. Terms explicitly used herein, which may also appear in any disclosure incorporated by reference, should be given the meaning most consistent with the specific concepts disclosed herein. [Brief explanation of the drawings]

[0009] Those skilled in the art will appreciate that the drawings are presented primarily for illustrative purposes and are not intended to limit the scope of the inventive subject matter described herein. The drawings are not necessarily to scale, and in some instances, various aspects of the inventive subject matter disclosed herein may be shown exaggerated or enlarged in the drawings to facilitate an understanding of different features. In the drawings, like reference characters generally refer to like features (e.g., functionally similar and / or structurally similar components).

[0010] [Figure 1A] FIG. 1A illustrates exemplary process steps for creating meta-atoms on curved surfaces. [Figure 1B] FIG. 1B illustrates exemplary process steps for creating meta-atoms on curved surfaces. [Figure 1C] FIG. 1C illustrates exemplary process steps for creating meta-atoms on curved surfaces. [Figure 1D] FIG. 1D illustrates exemplary process steps for creating meta-atoms on curved surfaces. [Figure 1E] FIG. 1E illustrates exemplary process steps for fabricating meta-atoms on curved surfaces. [Figure 1F] FIG. 1F illustrates exemplary process steps for fabricating meta-atoms on curved surfaces. [Figure 1G]FIG. 1G shows an example of a vacuum press intended to apply a meta-optic film to a non-planar optical substrate. [Figure 1H] FIG. 1H shows the vacuum press of FIG. 1G in which the meta-optic film is applied to and conforms to the non-planar surface of the optical substrate. [Figure 2] FIG. 2 shows a hybrid meta-optical system. [Figure 3-1] FIG. 3 is a plot of the simulated modulation transfer function (MTF) of the objective optics of FIG. [Figure 3-2] FIG. 3 is a plot of the simulated modulation transfer function (MTF) of the objective optics of FIG. [Figure 4A] FIG. 4A shows another design of a hybrid meta-optical system. [Figure 4B] Figure 4B plots the simulated MTF of the hybrid metasurface optical system in Figure 4A at various wavelengths. [Figure 4C] Figure 4C plots the simulated MTF of the hybrid metasurface optical system in Figure 4A at various wavelengths. [Figure 4D] Figure 4D plots the simulated MTF of the hybrid metasurface optical system in Figure 4A at various wavelengths. [Figure 5] FIG. 5 shows the optical system of a conventional night vision goggle, along with ray tracing and some specifications. [Figure 6A] FIG. 6A illustrates another design of a hybrid meta-optical system in which all surfaces are planar. [Figure 6B] Figure 6B plots the simulated MTF of the hybrid metasurface optical system of Figure 6A at various infrared wavelengths. [Figure 6C] Figure 6C plots the simulated MTF of the hybrid metasurface optical system in Figure 6A at various infrared wavelengths. [Figure 7A]Figure 7A shows an ocular hybrid meta-optical system that integrates two nonplanar metasurfaces on a curved substrate. [Figure 7B] FIG. 7B is a plot of the absolute value of the optical transfer function of the eyepiece of FIG. 7A. [Figure 7C] FIG. 7C shows another embodiment of an eyepiece hybrid meta-optical system that integrates two planar metasurfaces on a planar substrate. [Figure 7D] FIG. 7D is a plot of the absolute value of the optical transfer function of the eyepiece of FIG. 7C. [Figure 8A] Figure 8A illustrates a hybrid meta-optical system that combines a planar metasurface and a refractive lens. [Figure 8B] FIG. 8B is a plot of the absolute value of the optical transfer function for the meta-optical system of FIG. 8A versus various wavelengths. [Figure 8C] FIG. 8C is a plot of the absolute value of the optical transfer function for the meta-optical system of FIG. 8A versus various wavelengths. [Figure 8D] FIG. 8D is a plot of the absolute value of the optical transfer function for the meta-optical system of FIG. 8A versus various wavelengths. [Figure 8E] Figure 8E illustrates a hybrid meta-optical system that combines a planar metasurface with a refractive lens. [Figure 8F] FIG. 8F plots the absolute value of the optical transfer function for the meta-optical system of FIG. 8E for various ray incident angles. [Figure 9A] Figure 9A shows a hybrid graded-index (GRIN) meta-optical system comprising a planar metasurface integrated with a GRIN layer. [Figure 9B] Figure 9B shows a hybrid GRIN meta-optical system with a curved metasurface integrated with a GRIN layer. [Figure 9C] Figure 9C shows a hybrid GRIN meta-optical system comprising a curved metasurface integrated with a GRIN layer with embedded apertures. [Figure 10A] FIG. 10A shows a helmet-integrated near-eye display system with flat, thin optics that collimate and redirect the image from the projector toward the viewer. [Figure 10B] FIG. 10B shows a helmet-integrated near-eye display system that includes a curved thin optical element that is conformally integrated into the helmet visor and redirects the image from the intermediate plane toward the viewer. [Figure 10C] FIG. 10C shows a near-eye display system integrated on a helmet, with multiple thin optical elements integrated into the helmet visor to redirect the image towards the viewer. [Figure 10D] FIG. 10D shows a near-eye display system integrated on a helmet, comprising multiple thin optical elements and a projector integrated into the helmet's visor. [Figure 10E] FIG. 10E shows a helmet-integrated near-eye display system with a projector that illuminates from inside the helmet. [Figure 11A] FIG. 11A shows a meta-optical projector (or meta-optical imager) that uses a planar meta-optical element with a metasurface to project (or capture) images with a panoramic FOV and high resolution. [Figure 11B] FIG. 11B shows another embodiment of a meta-optical projector (or meta-optical imager) that uses a curved meta-optical element with a metasurface to project (or capture) images with a panoramic FOV and high resolution. [Figure 11C] FIG. 11C shows another embodiment of a meta-optical projector (or meta-optical imager) that uses a curved meta-optical element with a metasurface to project (or capture) images with a panoramic FOV and high resolution. [Figure 12] FIG. 12 shows a near-eye display system integrated into a helmet with a meta-optical projector that illuminates from inside the helmet. [Figure 13A]Figure 13A shows a near-eye display system integrated on a helmet with an embedded array of wide-angle meta-optical projectors using a planar substrate on which a metasurface is disposed. [Figure 13B] Figure 13B shows a near-eye display system integrated on a helmet with an embedded array of wide-angle metaprojectors using a curved substrate on which the metasurface is disposed. [Figure 14A] FIG. 14A shows a near-eye display system integrating a meta-optical projector and a meta-optical imager with a planar substrate for an eye-tracking device. [Figure 14B] FIG. 14B shows a near-eye display system that integrates a meta-optic projector and a meta-optic imager with a curved substrate for an eye-tracking device. [Figure 15] FIG. 15 illustrates exemplary process steps for transferring optically active features patterned on a planar substrate to a non-planar surface of another substrate. [Figure 16] FIG. 16 includes a microscope image (magnified) and a scanning electron microscope photograph (inset) of a meta-atom transferred from a planar surface to a non-planar surface according to the process steps of FIG. [Figure 17A] FIG. 17A plots the results of mechanical deformation tests on microscale patterned features transferred from a planar surface to a non-planar surface according to the process steps of FIG. [Figure 17B] FIG. 17B plots the results of mechanical deformation tests on microscale patterned features transferred from a planar surface to a non-planar surface according to the process steps of FIG. [Figure 18A] FIG. 18A illustrates an example of a hybrid meta-optical system in which metasurfaces are combined with binary optical elements in the system. [Figure 18B] FIG. 18B illustrates an example of a hybrid meta-optical system in which a metasurface is combined with a multi-stage optical element. DETAILED DESCRIPTION OF THE INVENTION

[0011] 1. Introduction

[0012] The technology described herein relates to nonplanar metasurfaces and fabrication methods for forming metasurfaces on planar and nonplanar surfaces using industry-standard fabrication techniques. In some embodiments, the nonplanar surface is a smoothly varying curved surface (e.g., a spherically convex or spherically concave, cylindrically convex or cylindrically concave surface), where the radius of curvature of the surface may be as small as 10 mm, or even as small as 1 mm. In some embodiments, the nonplanar surface is piecewise continuous across a convex or concave surface (e.g., the exterior surface of a hexagonal or other polygonal prism or a geodesic dome). In some embodiments, the nonplanar surface is a stepped, multi-tiered surface or a multi-layered surface, as further described below. In some embodiments, the nonplanar surface is a freeform surface that can include undulations in multiple directions or combinations of the other nonplanar surfaces mentioned above.

[0013] A variety of structures can be obtained by patterning meta-atoms on non-planar surfaces. The resulting structures include curved meta-optical devices with at least one metasurface disposed on an optical component with bilateral curvature (e.g., a dome- or shell-shaped structure). The resulting structures include conformal meta-optical devices with at least one metasurface disposed on the non-planar side of the optical component. The opposite side of the optical component may be flat (e.g., a plano-convex lens). The resulting structures include 2.5D meta-optical devices, which include a combination of 2D planar and 3D non-planar elements, or multilayer or multi-level structures extended from the 2D plane (e.g., GRIN or multi-level DOE structures).

[0014] The fabrication methods are also applicable to the fabrication of other types of microstructures, such as diffractive optical elements, diffraction gratings, waveguides, integrated optical circuits, MEMS, and the like, with curved, conformal, and / or multilayer form factors. Several meta-optical systems including planar and / or non-planar metasurfaces are also described. Such meta-optical systems can be implemented as hybrid meta-optical systems that combine planar and / or non-planar metasurfaces with at least one other optical element having at least one planar or non-planar surface. The other optical element can include a refractive optical element, a reflective optical element, and / or a diffractive optical element (DOE). In some cases, at least one of the other optical elements (e.g., the DOE) can include a multi-stage optical element having multiple patterned features. Hybrid meta-optical systems can include multi-layer material stacks within the system. The meta-optical devices described herein can be used in applications such as imaging, sensing, near-eye displays, and endoscopy systems.

[0015] The meta-optical devices described herein are based on metasurfaces. Metasurfaces consist of a collection of so-called meta-atoms arranged in close proximity to one another (e.g., on the surface of a substrate or wrapped in a thin polymer film). The meta-atoms are arranged to provide at least one optical function (e.g., focusing, patterning, filtering, collimating, aberration correction, etc.) to light incident on the metasurface having a specific wavelength or range of wavelengths for performing an optical function. The meta-atoms of a metasurface can all have the same shape (e.g., silicon pillars) or can have a variety of shapes, some of which are described below. The meta-atoms can include microscale structures (sizes on the order of 100 nanometers to 10 microns) and / or nanoscale structures (sizes on the order of 100 nanometers or less). The meta-atoms can be sub-wavelength in size and / or can include sub-wavelength feature sizes, where the wavelength is the wavelength of the radiation for which the meta-optical device is used. The meta-atoms can be formed from metals, semiconductors, and / or insulators, which can be patterned using microfabrication processes.

[0016] It is the combination of metaatom parameters—i.e., the metaatom placement (e.g., the spacing and arrangement of metaatom locations), the size of the metaatoms, the material of the metaatoms, and the shape of the metaatoms—that imparts the optical function to a metasurface. The superposition of light's interaction with the metaatoms determines the resulting optical function. Those skilled in the art of optical modeling can construct numerical models that represent the optical behavior of a metasurface and use the numerical models to design metasurfaces that provide one or more desired optical functions. While such optical modeling is similar to modeling the beam modulation behavior (e.g., focusing) of a diffractive optical element or Fresnel lens with subwavelength features, metasurfaces can provide more sophisticated optical functions due to the number of different parameters of the controllable metaatoms. For example, metasurfaces can provide optical functions that selectively depend on, for example, polarization alone, wavelength alone, or angle of incidence alone, or some combination of these optical properties.

[0017] The concepts related to the formation of nonplanar metasurfaces can be applied to thin optical elements, a type of optical element that includes meta-optical elements, as further described below. Thin optical elements have a plurality of patterned features (e.g., optical diffractive features) disposed on their surface and can provide at least one optical function to light incident on the thin optical element. The light has at least one specific wavelength for the thin optical element to perform the at least one optical function. The features of the thin optical element can be transferred from a planar surface to a non-planar surface in a similar manner to how meta-atoms formed on a planar surface can be transferred to a non-planar surface. All optical systems and components described herein can be used bidirectionally. For example, if the optical element is combined with an image sensor, a given optical system can be used for imaging or sensing. Alternatively, if the image sensor is replaced with a light source (e.g., one or more light-emitting elements, e.g., LEDs, or an image source, e.g., a microdisplay), the same optical system can be used to project an image or pattern.

[0018] 2. Conformal Metasurface Optical Fabrication Process

[0019] 1A-1F illustrate one embodiment of a process for fabricating a nonplanar metasurface optical device 100 (shown in FIG. 1F) having meta-atoms 120 disposed on one or more nonplanar (e.g., curved) surfaces. The exemplary process can begin with fabricating the meta-atoms 120 on a handler substrate 105 using deep ultraviolet lithography, electron beam lithography, nanoimprinting, nanostencil lithography, or other patterning techniques. In the illustration of FIG. 1A, multiple meta-atoms 120 are disposed on a planar surface to form a planar metasurface 108.

[0020] The planar metasurface 108 can be disposed on a sacrificial layer 110. The sacrificial layer 110 (in this example, an oxide layer) can be formed on a handler substrate 105, such as a handler wafer (e.g., a full silicon wafer). In some cases, the handler substrate 105 can function as the sacrificial layer. The sacrificial layer 110 can then be removed (e.g., etched away or mechanically removed by lapping, polishing, or dicing) to separate the meta-atoms 120 from the handler substrate 105. In an example exemplary process, as shown in FIG. 1B, a thermoplastic material 130 can be applied in a liquid or molten state to the planar metasurface 108 to form a film that encapsulates the meta-atoms 120. The thermoplastic film can be optical in some cases, but when transferred to another surface, in some embodiments, it can have a non-optical surface. The non-optical surface can be made optical by recoating the surface with another material having a similar refractive index. When encasing the meta-atom 120, the thermoplastic 130 contacts multiple surfaces of the meta-atom (e.g., at least two surfaces at an angle to each other, at least four surfaces for a cubic-shaped meta-atom, etc.). In some embodiments, the thermoplastic 130 contacts all surfaces of the meta-atom that are not in contact with the underlying substrate. The thermoplastic 130 may be optically transparent or may exhibit low optical loss (e.g., less than 20% optical attenuation). In some cases, the thermoplastic 130 can be coated using a solution-based process (e.g., by first dissolving the thermoplastic in a solvent and then spin-coating, spray-coating, or dip-coating). Alternatively, a hot-melt coating process can be used, in which the thermoplastic 130 is heated above its glass transition temperature, causing it to flow and form a coating layer on the meta-atom 120. The glass transition temperature of the thermoplastic 130 can be well below the melting temperature of the material from which the meta-atom 120 is formed (e.g., inorganic materials, such as silicon and / or oxides).

[0021] Thermoplastic 130 is a material that can soften and flow when heated above its glass transition temperature and return to a rigid solid when cooled below its glass transition temperature without any degradation of the plastic. Examples of thermoplastics that can be used to transfer the planar metasurface 108 include, but are not limited to, polyester, polystyrene (PS), polycarbonate (PC), polypropylene (PP), acrylic, polyethylene (PE), polyethylene terephthalate (PET or PETE), polyethylene terephthalate glycol (PETG), polyvinyl chloride (PVC), acrylonitrile butadiene styrene (ABS), polyether ether ketone (PEEK), polyimide, and polyamide. Thermoplastic 130 can be deposited to a thickness ranging from 0.1 micron to 500 microns, although thicker layers may be used in some cases. In some embodiments, to aid in handling the thermoplastic layer, a more mechanically stable, thicker, and more flexible film (e.g., polydimethylsiloxane (PDMS)) can be temporarily adhered to the thermoplastic layer before peeling it off.

[0022] After the thermoplastic 130 hardens, the sacrificial layer 110 can be etched away, and the thermoplastic 130 and meta-atoms 120 can be separated as a free-standing meta-optical film 150, as shown in FIG. 1C. The meta-optical film 150 is also more commonly referred to as a thin optical film. Alternatively, mechanical removal (e.g., lapping, polishing, or dicing) and / or etching of the handler substrate 105 can be performed to form the free-standing meta-optical film 150. If the handler substrate 105 is removed by mechanical removal and / or etching, the sacrificial layer 110 may be omitted. The thermoplastic 130 can maintain the spacing between the meta-atoms of the metasurface 108 after the meta-atoms 120 are separated from the handler substrate 105. Because the thermoplastic 130 is flexible and can be further flexible by heating, the meta-optical film 150 can then be applied to a non-planar surface. In some cases, multiple meta-optical films 150 can be stacked and bonded together to form a flexible multilayer meta-optical film 152, as shown in FIG. 1D.

[0023] Stacking meta-optical films 150 can form optically coupled bilayer or multilayer metasurfaces, for example, to enhance light dispersion design. In such cases, two meta-optical films 150 can be stacked with their metasurface sides (including meta-atoms 120) facing each other. Stacking meta-optical films 150 can also form multifunctional optical devices containing multiple functionally distinct and independent metasurface layers. In such embodiments, meta-optical films 150 can be stacked such that the metasurface side of at least one film faces away from an adjacent film in the stack, resulting in a space between the metasurface sides (and meta-atoms 120) of different meta-optical films, as shown in FIG. 1D . In some cases, bare thermoplastic films 154 can be inserted between or adjacent to the metasurfaces as spacers. In some embodiments, bare thermoplastic films 154 can be applied to the metasurface sides of the films (as shown in FIG. 1D ) to protect or space the meta-atoms 120 from the surface to which the meta-optical films 150 are applied.

[0024] Compared to existing multilayer metasurface fabrication methods based on elastomers (e.g., silicone), the mechanical rigidity of thermoplastics (130) at room temperature facilitates the lamination process, potentially enabling precise layer-to-layer alignment with deep submicron precision, similar to wafer bonding processes for 3D or 2.5D integrated circuits. Removal and transfer of polymer films is simpler compared to repeated multilayer lithography and "planarization," especially on non-planar surfaces.

[0025] The meta-optic film 150 can then be compression molded into its final non-planar shape using at least one mold 165. Such compression molding is shown in FIGS. 1E and 1F. The meta-optic film 150 can be heated during compression molding to deform the film and form it into its final shape, whereupon it can be cooled. After the meta-optic film 150 has been molded (e.g., onto the surface of the optical element 160, or into its final shape if two molds are used instead of molding onto the optical element 160), the mold 165 can be removed, leaving behind the non-planar metasurface optical device 100. The non-planar metasurface optical device 100 can, in some cases, comprise only the molded non-planar meta-optic film 150, or can comprise one or more meta-optic films 150 molded and adhered to the surface of the optical element 160 (e.g., optical lens, window, filter, wave plate, prism, diffraction grating, etc.) or other surface.

[0026] In some cases, meta-atom 120 can be bonded to the surface of optical element 160 (or the surface to which meta-optical film 150 is applied), and thermoplastic material 130 can be etched or dissolved away. For example, meta-atom 120 can be in direct contact with the surface of optical element 160 and optically contact bonded to optical element 160. In some cases, heat can be applied (e.g., sintered) to bond meta-atom 120 to the surface. Alternatively, a thin adhesive layer can be used to bond meta-atom 120 to the surface of optical element 160. In some embodiments, thermoplastic material 130 bonds meta-atom 120 to the surface of optical element 160 or other surface.

[0027] Those skilled in the art will appreciate that other thermoforming or molding methods can be used in place of compression molding in this process. For example, a vacuum press 170, shown in Figures 1G and 1H, can be used to form meta-optical film 150 or multilayer meta-optical film 152. In Figure 1G, optical element 160 is placed in vacuum press 170, and thermoplastic film 132 is applied to optical element 160 within vacuum press 170. Thermoplastic film 132 is heated, and a vacuum is applied to the press via vacuum tube 175. Upon application of the vacuum, thermoplastic film 132 is draped over optical element 160, as shown in Figure 1H. Thermoplastic film 132 retains the shape of the curved outer surface of the optical element upon cooling.

[0028] The inventors have found that it can be beneficial to invert the vacuum press 170 so that the applied vacuum draws the thermoplastic film 132 upward against gravity and onto the optical element 160. The thermoplastic film 132 can be supported from below by a polymer mesh (not shown), allowing the thermoplastic film 132 to be heated uniformly without sagging or distorting before the vacuum is applied. Furthermore, by carefully controlling the rate at which the vacuum is applied, sudden and uneven changes in pressure across the thermoplastic film 132 can be avoided. Such an arrangement can reduce distortion of the metasurface when cast onto the optical element 160.

[0029] When fabricating a nonplanar metasurface optical device 100, a refractive, reflective, or diffractive optical element 160 can function as a mold in addition to providing the optical function for the resulting optical device 100. Such a nonplanar metasurface optical device 100, sometimes referred to as a nonplanar hybrid metaoptical device, can comprise one or more metasurfaces conformally covering at least a portion of a nonplanar refractive optical surface.

[0030] The process for fabricating the above-described nonplanar metasurface optical device 100 leverages industrial-scale thermoplastic forming (TPF) processes (e.g., melt coating, lamination, and thermoforming or molding) to enable large-area, scalable manufacturing. The known advantages of TPF for determining precise shape and established TPF modeling techniques allow for prediction and control of metasurface deformation throughout the process. For example, the layout pattern of meta-atoms (or thin optical features) fabricated on the handler substrate 105 can be pre-distorted to compensate for and counteract subsequent distortions that would otherwise be caused by deformation of the thermoplastic sheet when the thermoplastic sheet is transferred onto a curved surface.

[0031] 3. Hybrid meta-optical devices

[0032] The basic architecture of a hybrid meta-optical device (sometimes more generally referred to as a hybrid thin optical device) consists of a substrate and at least one meta-optical film 150 (or thin optical film) integrated with the substrate. The substrate of a hybrid meta-optical device can be a refractive optical element 160, as described above, or a reflective optical element or a diffractive optical element, although other optical substrates can also be used. In some cases, a hybrid meta-optical device can include two or more optical elements 160 (e.g., a stack of optical elements), one or more of which can be integrated with one or more meta-optical films 150. The substrate can be initially flat (in the case of a planar hybrid meta-optical device), or curved or freeform (in the case of a non-planar hybrid meta-optical device). In some cases, the substrate comprises multiple layers. The substrate can be optically transparent and can be designed to perform refractive and / or diffractive optical functions (e.g., focusing, divergence, spectral separation, etc.). Some embodiments of a hybrid meta-optical device can further include one or more photodetectors and / or one or more light sources integrated with the hybrid meta-optical device.

[0033] The hybrid meta-optical devices described herein can further comprise one or more additional thin optical elements. Examples of thin optical elements include subwavelength optical elements, metasurfaces, meta-optical films 150, metamaterials, diffractive optical elements (DOEs), holographic optical elements (HOEs), gradient index (GRIN) optical elements, wafer-level optics (WLOs), micro-optical elements, etc. Thin optical elements can be patterned and transferred to planar or non-planar hybrid meta-optical devices using the TPF techniques described above in connection with Figures 1A through 1H. Thin optical elements may be positioned on, inside, outside, conformal to, or adjacent to the substrate of the hybrid meta-optical device. In some cases, light is coupled into a photodetector or from a light source through the hybrid meta-optical device. To accommodate geometric deformations, the unit structures (e.g., subwavelength arrays of meta-atoms in the case of metasurfaces) are designed and configured according to the shape of the substrate to provide the desired optical function and quality. Multiple thin optical elements may be used in a hybrid meta-optical device.

[0034] The conformal thermoplastic film integration process allows one or more meta-optical films 150 to be assembled on the same substrate. For example, thin optical elements, apertures, shadow masks, filters, transmissive coatings, and / or reflective coatings can be integrated or patterned on or within one or more thermoplastic films and laminated to other layers on the substrate. The apertures may be used to limit the spatial and / or angular range of the optical beam. Reflectors or reflective metasurfaces can be used to fold the beam between specific layers, reducing the overall thickness of the optical system. The refractive index contrast of various layers can also be used to enable beam folding via total internal reflection (TIR). Thus, the 3D multilayer material stack effectively serves as an opto-mechanical integration platform. The fabrication process is scalable to larger substrates (e.g., optical elements with a diameter of 50 mm). Several embodiments, variations, designs, and applications of hybrid optical devices are described below.

[0035] 4. Hybrid Imaging and Eyepiece Optics

[0036] Hybrid meta-optical devices, as described in this section, can be used in imaging, sensing, display, and eyepiece optics (e.g., night vision goggles (NVG), virtual / augmented reality (AR / VR) systems, etc.).

[0037] Conventional NVG objective lenses typically have a field of view (FOV) of approximately 40° and are typically composed of more than six refractive lenses, resulting in an overall system aspect ratio (length / aperture diameter) of greater than 2:1, both of which continue to increase as FOV and resolution requirements increase. The overall aspect ratio of a conventional NVG optical system incorporating an eyepiece and image inverter typically exceeds 6:1, thereby resulting in a relatively large torque load on the wearer.

[0038] Flat optical elements (planar metasurfaces or DOEs) have been recognized as an alternative to traditional bulk optics, offering considerable size, weight, and power advantages. However, they suffer from significant chromatic and Seidel aberrations in large-aperture systems. Current achromatic metalenses rely on dispersive design of meta-atoms, which imposes fundamental constraints on aperture size due to limited accessible group delay. Recently, zoned design methods have also been utilized, but these also suffer from a similar trade-off between performance (especially efficiency) and lens aperture size due to destructive interference as the number of zones increases. Furthermore, mutual coupling between meta-atoms, long considered a "silent problem" in the metasurface field, becomes significant and strongly wavelength-dependent for octave-band operation. Another approach involves optimized arrays of diffractive elements, but multi-stage diffractive elements only offer a fixed 1 / λ dispersion behavior, resulting in a trade-off between aperture size and numerical aperture (NA). On the other hand, inverse design by full aperture optimization is computationally infeasible for centimeter-sized optical elements.

[0039] Figure 2 shows a hybrid meta-optical system 200 that combines refractive and metasurface optical elements. The refractive component provides a large real group delay to address chromatic aberrations, while the metasurface effectively corrects Seidel aberrations, thereby addressing the aforementioned challenges associated with these aberrations. Ray-tracing simulation results are shown. In this example, the combined objective optics 210 and eyepiece optics 220 are comprised of only four optical elements, resulting in an overall length of less than 3 cm and an ultralight weight of 11 grams, while achieving unprecedented performance.

[0040] Hybrid meta-optical system 200 includes an objective lens 210 with three objective sub-lenses (OLs). OL-1 and OL-3 are hybrid lenses with metasurfaces 108 on both sides of the refractive lens, while OL-2 is a purely refractive lens. The metasurfaces 108 may be different from each other (e.g., have different meta-atom patterns). The meta-atoms are too small to be visible in FIG. 2 . One or more of the metasurfaces 108 may be implemented using the meta-optical film 150 described above. OL-3 has a flat back surface to facilitate integration and bonding with image intensifier 230. In one embodiment, one or more lenses in hybrid meta-optical system 200 are freeform lenses made of BaF2. In other embodiments, the lenses may be made of silica, polymers, and other conventional optical materials. Each metasurface 108 consists of an array of subwavelength structures (i.e., meta-atoms). Exemplary meta-atom shapes include pillars, disks, squares, rods, rings, fins, ridges, H-shapes, "+" shapes, freeform structures, and the like.

[0041] After the image is converted to one or more visible colors by the image intensifier 230, a fiber optic inverter 240 (twister) is used to invert the re-emitted image and display it at the eyepiece optics 220. At a distance equal to the image size (aspect ratio 1:1), the fiber optic inverter 240 is an efficient and compact means of inverting the image. Commercially available fiber inverters 240 can have core sizes as small as 4 μm, thereby extending the resolution up to 128 lp / mm. Other types of optical systems (e.g., metasurface optics) can also be used as image inverters.

[0042] The eyepiece optics 220 includes a concave lens 224 with a metasurface 108 integrated on its curved surface. The concave lens 224 is bonded to a planar polymer or glass spacer 222 (e.g., made of E48R). In one embodiment, the eyepiece optics 220 has an ultra-compact design (e.g., a total length along the optical axis of the system of 7.5 mm or less) and projects high-quality images from a fiber optic inverter to the eye for both red and amber colors. When the eyepiece optics 220 is used in an AR / VR system, a microdisplay may be used in place of the fiber optic inverter 240, and its image may be projected by the eyepiece optics 220 to the eye. Alternatively, the image may be relayed via other optical components to the focal plane of the image inverter 240 and then projected by the eyepiece optics 220 to the eye.

[0043] FIG. 3 plots the simulated modulation transfer function (MTF) of the objective optics 210 of FIG. 2. The plots are for both tangential (T) and sagittal (S) rays. Within a 100° FOV in the NIR, the objective optics 210 achieves a resolution of over 140 lp / mm. Over the mid-wave infrared (MWIR) band (3000-5000 nm), the objective optics 210 achieves near-diffraction-limited resolution of over 110 lp / mm. By using only two hybrid meta-optic lenses (i.e., OL1 and OL3, omitting OL2), the resulting objective optics can be designed to achieve even greater than 70 lp / mm resolution in both the near-infrared (NIR) and mid-infrared (MIR) bands over a 100° FOV.

[0044] FIG. 4A shows another design of a three-lens hybrid meta-optical system 400 that can be compared with the conventional eight-lens optical system 500 shown in FIG. 5. Figures 4B, 4C, and 4D plot the MTF for wavelengths of 750 nm, 1150 nm, and 1550 nm, respectively. For the hybrid meta-optical system of FIG. 4A, the input aperture is expanded to 25 mm, and conformal metasurfaces 108 are similarly positioned on either the curved or planar optical surfaces of hybrid meta-optical lenses OL-1 and OL-3. The exemplary design consists of three optical elements: two hybrid meta-optical lenses (OL-1 and OL-3) with metasurfaces 108 on two opposing surfaces of each lens, and one refractive-only lens (OL-2). The total track length is less than 24 mm (aspect ratio less than 1:1). This design achieves a FOV of greater than 80° with a resolution of greater than 130 lp / mm. The focal radius is maintained between 1 μm and 6 μm throughout the entire FOV.

[0045] We compare the hybrid metasurface optical system in Figure 4A with an existing conventional NVG objective lens design shown in Figure 5. The conventional design consists of eight glass lenses with an input aperture diameter of approximately 23 mm and a total track length of 46 mm (aspect ratio 2:1). This design provides a 40° field of view with a resolution of 40 lp / mm. As the angle of incidence increases, the focal spot size increases by more than six times, from a radius of 4 mm at normal incidence to 27 mm at an incidence angle of 19°. Therefore, compared to the conventional NVG design, the hybrid metasurface optical system in Figure 4A: The FOV is expanded by approximately 2 times, approaching natural field of view. Resolution improved by more than three times, The overall length is reduced by half, and This results in a reduction in the number of optical elements by a factor of two.

[0046] FIG. 6A illustrates another design for a hybrid meta-optical system 600 in which all substrate surfaces forming the objective lens are planar. Specifically, Metalens 1 and Metalens 2 each include two planar metasurfaces 108 formed on both surfaces of each metalens. The metasurfaces 108 may be different (e.g., have different meta-atom patterns). Planar spacers (Spacer 1, Spacer 2) are used between the metalens and the image plane 650 (where an image intensifier can be mounted). While the performance of this all-planar meta-optical system 600 is not as good as the curved meta-optical systems 200, 400 of FIGS. 2 and 4A, it still outperforms the traditional refractive-only design ( FIG. 5 ), achieving a nearly 100° FOV and a compact form factor. Any of the objective optical elements of FIGS. 2, 4A, and 6A can be used with the hybrid meta-optical system 200 of FIG. 2. Figures 6B and 6C plot the simulated MTF for the hybrid metasurface optical system of Figure 6A at near-infrared wavelengths (Figure 6B), and mid- and long-wavelength infrared (Figure 6C).

[0047] Figures 7A and 7C show two variations 700, 750 of an eyepiece hybrid meta-optical system. In the embodiment of Figure 7A, two metasurfaces 108 are conformally integrated onto a non-planar surface of a curved substrate 710. A first surface of the curved substrate is concave, and a second surface of the curved substrate 710 is convex. A wide FOV of over 80° achieves near-diffraction-limited performance. Figure 7B plots the absolute values ​​of the optical transfer functions for tangential rays (solid lines) and sagittal rays (dotted lines) at various off-axis distances from approximately 1 mm to approximately 8 mm.

[0048] In the embodiment of Figure 7C, a single planar substrate 760 is used, with two planar metasurfaces 108 formed on each of the substrate's 760 planar surfaces. The eyepiece meta-optical system 750 provides an FOV of approximately 60°. The absolute values ​​of the optical transfer function of the eyepiece of Figure 7C are plotted in Figure 7D for tangential rays (solid lines) and sagittal rays (dotted lines) at various off-axis distances from approximately 1 mm to approximately 6 mm. The eyepiece designs of both Figures 7A and 7C contain only a single discrete component and are very compact.

[0049] 8A-8D illustrate that a planar meta-optical element can be combined with one or more refractive lenses to form a hybrid meta-optical system with improved optical performance. Hybrid meta-optical system 800 incorporates two planar metasurfaces 108 on a planar optical element 810, one refractive lens 820, and a spacer 830, resulting in a 60° FOV with high resolution (approximately 130 lp / mm or greater). Meta-optical system 800 has an f-number of 0.6. The total track length of meta-optical system 800 must be 20 mm or less. The numerical aperture of the meta-optical system is 12 mm. The resolution and FOV of meta-optical system 800 can be improved by forming two metasurfaces 108 on a curved optical element instead of on the planar optical element 810. The plots in Figures 8B, 8C, and 8D plot the absolute values ​​of the optical transfer function for three different wavelengths, tangential rays (solid lines), sagittal rays (dotted lines), and angles of incidence ranging from 0 to 30 degrees.

[0050] FIG. 8E shows another embodiment of a hybrid meta-optical system 801, comprising one planar metasurface 108 and one refractive lens 820 on a planar optical element. A glass plate 811 near the image plane may be the cover glass of an image sensor. The glass plate 811 may also include an optical filter element. The hybrid meta-optical system 801 operates at visible and / or near-IR wavelengths and provides an 80° FOV with near-diffraction-limited performance. The hybrid meta-optical system 801 has an f-number of 3.3. The design is ultra-compact, with a total track length of 2 mm. The absolute values ​​of the optical transfer function of the hybrid meta-optical system 801 are plotted in FIG. 8F for tangential rays (solid line) and sagittal rays (dotted line) over a range of angles of incidence from 0 to 40 degrees.

[0051] 5.GRIN Meta-Optical System

[0052] In another embodiment, the planar and / or non-planar metasurface 108 can be integrated with a multilayer optical structure or a gradient index (GRIN) structure. Some exemplary GRIN meta-optical systems 901, 902, 903 are illustrated schematically in FIGS. 9A-9C. A GRIN meta-optical system includes one or more GRIN optical elements 910, 912 and at least one metasurface 108 conformally stacked together to form an integrated flat ( FIG. 9A ) or curved ( FIGS. 9B, 9C ) GRIN meta-optical system. One or more apertures 920 may be integrated on, internally, externally, or adjacent to the GRIN meta-optical system. The apertures 920 can be formed, for example, by patterning an absorber 930 on the surface of the GRIN optical element 910. The absorber can include a metal or a semiconductor.

[0053] In some embodiments (e.g., in FIG. 9C ), the first GRIN optical element 910 and / or the second GRIN optical element 912 can have one or more apertures patterned on their surfaces. In the illustrated example, the first GRIN optical element 910 uses an engineered refractive index profile to direct light at various angles of incidence toward a single aperture 920. After passing through aperture 920, the light propagates through the second GRIN optical element 912 (or, in some embodiments, a homogeneous layer) and is then focused by the nonplanar metasurface 108 toward an image sensor, which can be located at the system's image plane 950. In some cases, another GRIN optical element or metasurface can be added between the illustrated GRIN meta-optical system and the image plane 950 to further redirect / shape the light.

[0054] The application of metasurfaces to GRIN optical elements combines the functions of metasurfaces for in-plane wavefront shaping and GRIN optical elements for out-of-plane light guiding within a highly compact form factor. Nonplanar metasurfaces are carefully designed to enable on-demand wavefront control, achieving desired optical performance and functionality, such as wide-angle FOV imaging with reduced aberrations. The front GRIN layer replaces the large front lens group commonly used in conventional wide-angle lens assemblies (e.g., fisheye lenses) to capture light within an ultra-wide FOV exceeding 180°. Intermediate GRIN optical elements can assist in further tailoring the light propagation. Compared to conventional optical components made of homogeneous media (e.g., lenses, free-space / plastic / glass spacers, etc.), curved 3D GRIN optical elements not only function as light propagation media but also as wavefront shaping elements, thereby significantly improving performance and reducing size when used with 2D or 3D metasurfaces.

[0055] Furthermore, the conformal polymer film integration process described above is suitable for transferring the metasurface 108 to nonplanar GRIN optical elements. GRIN optical elements can serve as opto-mechanical integration platforms. For example, thin optical elements, apertures, shadow masks, and / or reflective coatings can be patterned on one or more polymer layers, stacked together, and applied to the GRIN optical element. Apertures may be used to limit the spatial and / or angular range of the optical beam. Reflectors or reflective metasurfaces can be used to fold the beam between specific layers, reducing the overall thickness of the optical system. The refractive index contrast of the GRIN optical element (which can be implemented as multiple layers forming a step gradient in refractive index) can also be utilized to enable beam folding via total internal reflection (TIR).

[0056] The hybrid meta-optical devices described herein can further incorporate innovative zoom functionality without the need for mechanical moving parts, a feature that would be beneficial for endoscopy systems. A non-mechanical parfocal zoom lens using a multifunctional optical metasurface has been demonstrated, achieving a large step zoom ratio (10x), reduced distortion, and diffraction-limited image quality. Such metasurfaces designed for zoom functionality can be used as metasurfaces in the above-mentioned hybrid meta-optical systems, as described in International Publication No. PCT / US2022 / 077223, filed September 29, 2022, entitled "Multifunctional Metasurface Flat Optics," which is incorporated herein by reference in its entirety. By using a hybrid curved meta-optical architecture, the zoom lens approach can achieve a larger FOV / zoom ratio compared to flat architectures (e.g., switching between 240° and 20° FOVs in wide-angle and telephoto modes, respectively). Polarized multi-zoom metalens allows the metalens to switch between two modes under different polarizations of light. Alternatively, the image sensors used in such systems may integrate commercially available pixelated polarizer arrays aligned to each pixel on the image sensor. As a result, the imager can simultaneously capture images of the different polarizations produced by the polarization-multiplexed metalens. Such an approach enables camera architectures with high-performance imaging, ultra-wide FOVs, non-mechanical zoom, and very compact form factors (e.g., miniature endoscope cameras).

[0057] 6. Conformal metasurface-enabled display system

[0058] In another embodiment, thin optical elements and their associated manufacturing processes (e.g., as described above) can be used to improve the quality of display systems. Improved capabilities include high-resolution, wide-field-of-view (FOV) image projection, improved eye relief and eyebox, versatile display configurations, reduced size, weight, and power (SWaP), and the like. Thin, non-planar optical elements can be in various forms, such as subwavelength optical elements, metasurfaces, metamaterials, diffractive optical elements (DOEs), holographic optical elements (HOEs), wafer-level optics (WLOs), micro-optical elements, and the like. Generally, thin optical elements can be applied to near-eye displays (NEDs) (including head-mounted displays (HMDs) and head-in displays (HIDs)) and head-up displays (HUDs) for a wide range of applications. For example, forward components coupled (e.g., optically and / or mechanically) to the display system can be helmet visors, windshields, face shields, cockpit canopies, eyeglass lenses, goggles, add-on components, and the like. Display architectures and systems with non-planar thin optical elements feature large-area and / or multiple-region high-resolution image projection, and integration of display and sensing systems.

[0059] 6.1 NED Architectures and Systems Using Meta-Optical Elements

[0060] Near-eye displays (NEDs) can benefit from the above-described nonplanar thin optical elements and fabrication methods. When implemented in a NED system, the nonplanar thin optical elements may or may not include a nonplanar metasurface. An exemplary application could be integration with a spacesuit helmet or AR / VR goggles. FIGS. 10A-10E schematically illustrate a NED system 1000 comprising one or more projectors 1010 and one or more nonplanar thin optical elements 1050 functioning as redirecting optics and / or beam combiners. The projectors 1010 project one or more images toward a forward optical component 1020 (e.g., a helmet or goggle visor). The thin optical elements 1050 then redirect the images toward a viewer 1060. When used as a combiner, the thin optical elements 1050 can further combine the redirected / projected images with other information (e.g., real-world scenes, text, or images projected from other channels). The thin optical element 1050 may be in various forms, such as a meta-optic film 150, a metasurface 108, a DOE, an HOE, a coating, etc. The thin optical element 1050 may be configured to collimate, deflect, and / or reshape an image toward a viewer 1060. The thin optical element 1050 may be located in the front optical component 1020 of the NED system 1000 or on, within, or outside the NED system.

[0061] Thin optical elements may also contain embedded nanoparticles, such as silver or gold nanoparticles. Nanoparticle-embedded structures (e.g., meta-atoms) can be designed to selectively modulate the wavefront of specific wavelengths of light while transmitting other wavelengths unmodulated, thereby achieving functions such as optical beam combiners.

[0062] The NED system can include one or two visor layers. As shown in FIG. 10A, an intermediate surface 1030 (on which an intermediate image projected by a projector, scattering film, or microdisplay is formed or can be disposed) can be disposed on one layer (e.g., the outer visor or front optical component 1020 of the visor). The thin optical element 1050 can be disposed on the same optical component or another optical component (e.g., the inner visor or rear optical component 1022 of the visor). As an example (FIG. 10A), a single thin optical element 1050 is constructed on a planar substrate and mounted on the inner helmet visor.

[0063] In another embodiment (FIG. 10B), the thin optic 1050 and / or the interface 1030 may be non-planar. For example, the thin optic 1050 may be conformally integrated into the curved surface of one of the helmet's visors. The interface 1030 may also be non-planar and positioned on one of the helmet's visors.

[0064] In yet another embodiment, the projector 1010 projects one or more images directly toward the front optical component 1020, without an intermediate surface. A thin optical element 1050 (e.g., functioning as a redirecting optic and / or combiner) is disposed on the front optical component 1020 to redirect the image toward the viewer 1060. When used as a combiner, the thin optical element 1050 further combines the redirected / projected image with other information (e.g., real-world scenes, text, or images projected from other channels). Again, the thin optical element 1050 may take various forms, such as a meta-optic film 150, a metasurface 108, a DOE, an HOE, a coating, etc. The thin optical element 1050 can be designed to collimate, deflect, and / or reshape the image toward the viewer 1060.

[0065] In another example (FIG. 10C), one image projected from the projector 1010 is refracted by a first low-profile optical element 1050 positioned at a first position on the visor, and another image projected from the projector is reflected by a second low-profile optical element 1051 positioned at a second position on the visor. The second low-profile optical element 1051, unlike the first low-profile optical element 1050, may provide reflection rather than refraction. In another example (FIG. 10D), two images projected by two projectors 1010 are redirected toward the viewer 1060 by two low-profile optical elements 1050, 1051 that act as redirecting optics (or combiners). The second low-profile optical element 1051 may be the same as or different from the first low-profile optical element 1050. In yet another example (FIG. 10E), a single projector 1010 projects an image from inside the helmet. The image can be redirected toward the viewer 1060 by a single non-planar thin optical element 1050 disposed on the helmet's second optical component 1022. In some embodiments, the single non-planar thin optical element 1050 can combine the redirected image with a real-world scene, another image, or text from another source, so that the viewer 1060 can see both from the same region of the second optical component 1022. In the embodiment of FIGS. 10A-10B , in some embodiments, the thin optical elements 1050, 1051 can each include multiple thin optical elements (e.g., stacked thin optical elements). In some cases, each thin optical element 1050, 1051 includes at least one planar or non-planar metasurface 108, which can be implemented as a meta-optical film 150.

[0066] 6.2 Wide-angle image projection

[0067] Increasing the etendue (e.g., aperture size or FOV) of an image projector's optical elements radically improves the overall trade-off between eye relief, eyebox, and display FOV when the projector is used in a display system such as the one described here. Conventional wide-angle optical systems (e.g., fisheye lenses) typically require multiple lens assemblies to correct induced optical aberrations, significantly increasing the system's complexity, size, weight, and cost. To circumvent these issues, conventional multi-lens projectors can be replaced with highly compact meta-optical projectors (also known as meta-optical engines) that include a wide-angle FOV meta-optical device.

[0068] FIGS. 11A-11C show examples of such compact meta-optical projectors 1100, 1101, and 1102. Any of the meta-optical projectors in these figures can be used in the display systems of FIGS. 10A-10E. The meta-optical projectors include a meta-optical device 1110 optically coupled to an image source 1150 (e.g., a microdisplay or other light source). In some embodiments, the meta-optical device 1110 comprises one or more metasurfaces combined with at least one thin optical element, aperture, filter, or some combination thereof. It should be understood that the meta-optical projectors of FIGS. 11A-11C can be reconfigured and implemented as meta-optical imaging or sensing systems by replacing the image source 1150 with an image capture device, such as a CMOS or CCD image array. For example, instead of projecting an image from the image source 1150, the device operates optically in the reverse direction to record the image from the image source. According to some embodiments, the meta-optical projectors 1100, 1101, and 1102 can be reconfigured as thin optical projectors in which no metasurfaces are used. Alternatively, meta-optical device 1110 can be replaced by one or more thin optical elements.

[0069] In FIG. 11A, a meta-optical projector 1100 includes a planar meta-optical device 1110 and a microdisplay for image source 1150 (which is replaced by an image sensor to create a meta-optical imager). The meta-optical device 1110 includes a planar substrate 1112 and one or two metasurfaces 108 that can be disposed on the top and / or bottom surfaces of the substrate 1112. Such optical architectures can exhibit panoramic FOVs of 180° or more, high-resolution image projection across the entire FOV, and very compact optical architectures containing only a single meta-optical component, as further described in U.S. Pat. No. 10,979,635, filed June 8, 2020, entitled "Ultra-Wide Field-of-View Flat Optics," which is incorporated by reference in its entirety. The use of a curved substrate 1112 (as exemplified in FIGS. 11B and 11C) can further enhance the FOV, resolution, and / or facilitate device integration. When used in the display systems described herein, such meta-optical projectors can improve overall display performance by dramatically increasing the etendue of the projected image with expanded angular / spatial coverage. A wide FOV allows for multiple projection areas from a single projector, enabling additional functionality, e.g., multiple screens, stereoscopic viewing, etc. In some embodiments, the thin optical elements 1050, 1051 for redirecting and / or combining light beams can be co-designed based on the characteristics of the meta-optical projectors 1100, 1101, 1102 (e.g., to support an expanded FOV and / or higher resolution). Figure 12 shows an example of a NED application in which the thin optical element 1050 is extended to support an expanded FOV from any of the meta-optical projectors of Figures 11A-11C.

[0070] 6.3 Array-type microdisplay architecture

[0071] The highly compact meta-optical projectors of FIGS. 11A-11C may also allow for the integration of an array of such devices directly onto or near components positioned in front of the user (e.g., a helmet visor or AR / VR goggles), as shown in FIGS. 13A and 13B. The meta-optical projectors 1100 may be arranged in an array and configured individually or collectively to project images toward the viewer 1060. For example, an array of meta-optical projectors 1100 may be configured to provide a stereoscopic display by projecting images with different content, information, or optical characteristics. The image source 1150 and / or meta-optical device 1110 (or thin optical element) used in the projectors of FIGS. 13A (shown planar) and 13B (shown non-planar) may be planar or non-planar. The image source 1150 and / or meta-optical device 1110 (or thin optical element) may be positioned on, within, or external to the forward optical component 1020. In a non-planar configuration, for example, a flexible organic light emitting diode (OLED) display can be used as the microdisplay for image source 1150. Alternatively, a microLED display disposed on a flexible or curved substrate can be used as the microdisplay for image source 1150.

[0072] 6.4 Integrated Display and Sensing Devices

[0073] For example, a combination of a thin optical projector and a thin optical sensor can be integrated into an NED system to provide a variety of functions (e.g., 3D sensing, eye tracking, facial and / or iris recognition, etc.).

[0074] FIGS. 14A and 14B show an example of a NED system that combines image projection and image acquisition (or optical sensing). Replacing the microdisplay of some meta-optical projectors with an image sensor / detector and a light-emitting element array, while using similar meta-optical elements, can convert the meta-optical projector into a meta-optical imager or sensor. In an exemplary configuration, a light-emitting element 1410 is coupled with an illumination thin optics 1420 (e.g., a meta-optical element) to emit a probing beam (red or darker arrow in FIGS. 14A and 14B) toward an object / region (e.g., eye tissue for eye tracking / retinal imaging / iris recognition, a face for facial recognition, etc.), while light reflected by the object is coupled by a detection thin optics 1430 to an image sensor 1440 or at least one photodetector for data analysis. The illumination thin optics 1420 can be configured to generate a 2D / 3D spot array or a desired illumination pattern on the object / region of interest. Additionally, a single light emitter (e.g., a single LED) or multiple light emitters can be combined with an illumination thin optical element 1420 (e.g., a meta-optical element, DOE, or HOE designed as a holographic or spot generator) to generate a 2D / 3D spot array or illumination pattern on an object / area of ​​interest.

[0075] FIG. 14A is a schematic diagram of a near-eye display system 1400 that integrates a meta-optical projector 1100 using a planar substrate on which meta-atoms are disposed. The NED system 1400 can be adapted for eye tracking or eye sensing functions. Eye sensing functions include face / iris recognition and general eye imaging (e.g., retina, pupil, eyelid, sclera, pars plana, or iris). FIG. 14B is a schematic diagram of a near-eye display system 1401 that integrates a meta-optical projector 1102 and sensing / eye tracking functions using a curved substrate on which meta-atoms are disposed. The green (light) arrows (positioned between the outer red (dark) arrows) indicate the projected beam for the image display function. The red arrows indicate the probing and reflected beams for the eye tracking function.

[0076] Eye tracking systems typically measure the gaze point and position of the eye. Video-based optical eye tracking systems typically include a light source that generates a pattern (usually in the near IR) that illuminates the eye, and an imager that images the eye and the reflected beam / pattern. By analyzing the captured images and reflected optical signals, information about eye movements can be extracted. For example, the corneal reflection and the center of the pupil can be used as features to determine the direction of gaze. Reflections from various ocular tissues, such as the anterior surface of the cornea and the posterior surface of the lens, can also be used as tracking features. Internal eye features (e.g., retinal blood vessels) can also be used to more accurately track eye movements.

[0077] To integrate an eye tracking device into an NED system, the system includes at least one of: (1) an optical projector including illumination thin optics 1420 (e.g., meta-optics) and light emitting elements 1410 (or an emitter array) for illuminating ocular tissues (e.g., iris, cornea, fundus, retinal vessels, pupil, etc.) with a probe beam having a prescribed illumination pattern, and (2) an optical imager including detection thin optics 1430 and an image sensor 1440 and / or at least one photodetector for collecting reflected light and / or imaging the probe area. The system may further include (3) at least one display meta-optics projector 1100, 1102.

[0078] The illumination thin optics 1420 can be designed to generate and image multiple spot arrays or illumination patterns on different tissues / objects or at various locations in 3D space, allowing the multiple spot arrays or illumination patterns to be tracked independently (e.g., by an image capture device and image processor). The detection thin optics 1430 can be designed to capture images at various depths or tissues. The illumination thin optics 1420 and the detection thin optics 1430 can be designed to illuminate and image an object from various angles, respectively, to generate a 3-D image, e.g., stereo imaging. The compact form factor of a thin optical architecture (e.g., a meta-optical element) allows, for example, the integration and distribution of multiple projection and imaging sub-modules / sub-zones at different locations within the same NED system, as well as the integration of a light-emitting element array and an imager sensor.

[0079] Optical filters can be further integrated into the optical system (e.g., before the image sensor 1440) to transmit or block a desired range or ranges of wavelengths, polarization states, and / or angular components of light. Alternatively or additionally, any metasurface in the system can be designed to provide one or more required filtering functions.

[0080] 6.5 Demonstration of transfer of optically active features from planar to non-planar surfaces

[0081] Optically active features (meta-atoms in this example demonstration) were patterned on a flat surface and transferred to a curved surface (spherical) using the process and apparatus shown in FIG. 15. The process involves depositing a layer of amorphous silicon 1510 onto a substrate 1505 using plasma-enhanced chemical vapor deposition (PECVD). A lithographic process step was then used to pattern the amorphous silicon 1510 into a plurality of meta-atoms 120. In this example, the meta-atoms 120 had cylindrical shapes of different diameters and densities. The diameter of the pillars was less than 1 micrometer.

[0082] After the meta-atoms 120 are formed, they may be encapsulated in a polymer. In one method, polyethylene terephthalate glycol (PETG) dissolved in a 50:50 toluene / dichloromethane solvent solution was spin-coated onto the surface of the substrate 1505 to coat the meta-atoms 120. In a second method, polyvinyl chloride (PVC) dissolved in cyclohexanone was spin-coated onto the surface of the substrate 1505 to coat the meta-atoms 120. The spin-coated polymer was then annealed above its melting point to remove the solvent and release the solvent vapor, resulting in a polymer layer with the refractive index of the original undissolved polymer. The resulting thermoplastic 130 was approximately 5 microns thick, although thicknesses between 2 microns and 20 microns can be used.

[0083] To obtain a mechanically stable film of thermoplastic material 130, an industrially manufactured polymer film can be laminated onto the spin-coated polymer at 180°C (for PVC and PETG) using a roller and a PDMS interface layer to avoid adhesion between the roller and the laminated polymer film. The resulting multilayer polymer film can have a very uniform thickness that can be largely determined by the applied polymer film.

[0084] In the illustrated demonstration, the substrate 1505 was dissolved by etching, liberating the multilayer polymer film 1530 and the meta-atom 120. In this example, the substrate was a phosphosilicate glass, which has a very high etch rate in hydrofluoric acid. The etching solution was a 50:40:10 mixture of isopropyl alcohol (IPA), deionized water, and hydrofluoric acid (HF). The IPA improves the wetting of the glass and accelerates substrate dissolution. In another embodiment, the substrate 1505 can include a germanium layer that can be etched away with a hydrogen peroxide / ammonia solution and a suitable wetting agent.

[0085] Figure 16 shows a microscope image (larger view) and a scanning electron micrograph image (inset) of the features transferred onto the curved surface. In this demonstration, pillars were patterned on a planar substrate and transferred to the curved surface with a yield better than 99% following the process procedure described in connection with Figure 15. The meta-atoms 120 are transferred to the curved surface with high repeatability over a large area.

[0086] Figures 17A and 17B show the results of mechanical deformation testing of the thermoforming and transfer processes. In these studies, micron-sized squares 1710 were patterned across a planar substrate and then transferred to a cylindrically curved surface using the process procedure described in connection with Figure 15. In one study, the pattern density was varied (Figure 17A), and in another, the square size was varied (Figure 17B). A capping layer (double-sided elastomeric tape) on the curved surface reduced feature deformation. Feature elongation remained below 15% across a wide range of feature sizes (square sizes from 5 microns to approximately 18 microns on a side) and below 10% across a wide range of pattern densities (from approximately 20% pattern density to approximately 90% pattern density).

[0087] 7. Multi-stage meta-optical system

[0088] 18A illustrates an example of a hybrid meta-optical system 1801 in which a metasurface 108 is combined with a binary optical element 1810 in the system. The binary optical element 1810 can be formed, for example, from a polymer or inorganic material that is deposited and patterned on the metasurface 108 using a photolithography process. The binary optical element 1810 can be a diffractive optical element (DOE) or a refractive optical element. While the metasurface 108 and binary optical element 1810 are shown on a planar surface, they can be transferred onto non-planar surfaces using the techniques described above.

[0089] 18B illustrates an example of a hybrid meta-optical system in which a metasurface 108 is combined with a multi-stage optical element 1820 in the system. The multi-stage optical element 1820 can be formed, for example, from a polymer or inorganic material that is deposited and patterned onto the metasurface 108, for example, using a grayscale photolithography process. The multi-stage optical element 1820 can be a diffractive optical element (DOE) or a refractive optical element. The metasurface 108 and multi-stage optical element 1820 are shown on a planar surface but can be transferred onto non-planar surfaces using the techniques described above.

[0090] In the optical systems described above that include one or more metasurfaces, the metasurface (alone or in some embodiments in combination with a DOE) can be configured to modulate the phase, amplitude, polarization, and / or spectral properties of incident light. Optical systems that include one or more metasurfaces can also be configured to generate customizable modulation of an incident beam depending on the beam properties (e.g., angle, spatial, polarization, spectral properties, etc.). Optical systems that include one or more metasurfaces can also be configured to provide multiplexed functions, e.g., independent beam modulation of light of different wavelengths, polarization states, angles of incidence, etc.

[0091] In yet another embodiment of the hybrid configuration shown in Figure 19A, the hybrid meta-optical system incorporates at least one planar or non-planar metasurface and one or more multi-stage structures with varying thicknesses. As shown in Figure 19A, the non-planar metasurface layer may be integrated onto a non-planar structure, such as a multi-stage refractive and / or diffractive optical element (DOE) layer.

[0092] In yet another example of a hybrid configuration, shown in Figure 19B, a hybrid meta-optical system incorporates at least one planar or non-planar metasurface and one or more binary structures with varying thicknesses. As shown in Figure 19B, the non-planar metasurface layer may be integrated with a binary refractive and / or diffractive optical element (DOE) layer.

[0093] In the above embodiments, each unit of the multi-tiered structure may have a different width, height, and / or geometric shape. The width of each unit may vary between 0.1 and 10,000 times the wavelength. The height of each unit may vary between 0.1 and 10,000 times the wavelength. Metasurfaces and multi-tiered structures can be made of any type of optical material, such as glass, polymer, semiconductor, metal, etc. Multi-tiered structures may also be made of non-optical materials, for example, to function as mechanical / optomechanical structures. They may further include coatings (e.g., dielectric and / or metal coatings).

[0094] Hybrid multi-stage meta-optical structures can be fabricated using similar methods for fabricating metasurfaces on non-planar substrates described in this invention. Generally, metasurfaces and / or multi-layer structures may be fabricated using lithographic techniques, machining, or replication, either subtractively or additively, or a combination of these methods. Lithographic methods may include deposition or growth of metasurface layers and / or multi-layer structures, patterning (e.g., using photosensitive polymers), etching, etc. Exemplary techniques in this field include, but are not limited to, photolithography, multi-step lithography, grayscale lithography, electron beam direct writing, laser direct writing, etc. Machining methods involve fabricating metasurfaces and / or multi-stage structures by removing material from a substrate in a controlled manner. Exemplary techniques include, but are not limited to, laser ablation, focused ion beam milling, diamond turning, mechanical marking, etc. Replication methods involve fabricating multi-tiered structures and / or metasurfaces in polymers, glass, or other materials from masters / molds / stamps and can be fabricated using the methods described above. Such techniques include, but are not limited to, molding (e.g., injection molding), casting, hot embossing, nanoimprint lithography, etc.

[0095] In some embodiments, metasurface structures can be fabricated / integrated onto multi-tier structures in either a monolithic or hybrid manner. In monolithic fabrication / integration, the meta-atom and multi-tier structures are made of the same material and can be fabricated together using methods such as molding, casting, embossing, nanoimprinting, machining, direct laser writing, grayscale lithography, nanoimprint lithography, multi-step photolithography, and electron beam lithography. In hybrid fabrication / integration, the meta-atom and multi-tier structures are made of the same or different materials, and the metasurface can be fabricated onto the multi-tier structure using techniques such as molding, casting, embossing, nanoimprinting, machining, direct laser writing, and other lithography methods. For example, metasurfaces can be integrated onto multi-tier substrates using thermoforming methods similar to those described herein. In other methods, a layer of metasurface material can first be deposited onto the multi-tier structure and then patterned into meta-atom structures of different heights. Lithography tools (e.g., 3D printers provided by Nanoscribe GmbH of Eggenstein-Leopoldshafen, Germany) may be used to fabricate such structures. In one example, direct-write or maskless lithography (e.g., laser direct-write, electron-beam lithography, etc.) may be used, where the writing interface (depending on the height of the multi-tiered structure) can be precisely adjusted during the patterning process. Such methods can also be used to create masters / stamps / molds for use in replication-based methods.

[0096] In all optical configurations described herein, the metasurfaces, DOEs, refractive and / or reflective components can be configured to modulate the phase, amplitude, polarization, and / or spectral properties of incident light. They can also be configured to generate customizable modulation of the incident beam depending on the beam properties (e.g., angle, spatial, polarization, spectral properties, etc.). They may also be configured to provide multiplexing functions, e.g., independent beam modulation of light of different wavelengths, polarization states, angles of incidence, etc.

[0097] The meta-optical elements and systems described herein can be implemented in a variety of configurations, some of which are listed below: The meta-optical elements and systems can be fabricated using a variety of processes, some of which are listed below: (1) A method comprising the steps of: forming a thin optical element on a planar surface of a first substrate, the thin optical element comprising a plurality of patterned features arranged on the planar surface, the thin optical element providing at least one optical function to light comprising at least one particular wavelength incident on the thin optical element, the plurality of patterned features comprising one or both of microscale features and nanometer-scale features; encapsulating multiple surfaces of each of the plurality of patterned features on the planar surface with a thermoplastic material; peeling the thermoplastic material within which the plurality of patterned features are encapsulated from the planar surface to form a thin optical film; and applying the thin optical film onto a non-planar surface of a second substrate. (2) The method of (1), further comprising the step of pre-distorting a layout pattern of the plurality of patterned features to pre-distort the arrangement of the plurality of patterned features when forming a thin optical element on a planar surface, wherein pre-distorting the layout pattern compensates for distortion of the thin optical film when applied to a non-planar surface. (3) The method of (1) or (2), wherein the step of encapsulating the plurality of patterned features includes spin-coating a solution containing a thermoplastic material onto the plurality of patterned features, and after spin-coating, annealing the solution at a temperature above the glass transition temperature of the thermoplastic material. (4) The method of any one of (1) to (3), wherein the plurality of patterned features comprises meta-atoms and the thin optical film is a meta-optical film. (5) The method according to any one of (1) to (4), wherein the thermoplastic material comprises polyethylene terephthalate glycol (PETG). (6) The method of any one of (1) to (5), wherein peeling the thermoplastic material includes etching away a sacrificial layer of material underlying the plurality of patterned features on the first substrate. (7) The method according to any one of (1) to (6), wherein the step of applying the thin optical film includes the steps of heating the thin optical film and compression molding the thin optical film onto a non-planar surface. (8) The method according to any one of (1) to (7), wherein the step of applying the thin optical film includes the steps of heating the thin optical film and applying a vacuum to draw the thin optical film onto the non-planar surface. (9) The method of (8), wherein applying a vacuum pulls the thin optical film upward against gravity onto the non-planar surface. (10) The method according to any one of (1) to (9), wherein the thin optical film is a first thin optical film, and further comprising a step of laminating the first thin optical film onto the second thin optical film before applying the first thin optical film and the second thin optical film to the non-planar surface. (11) The method of any one of (1) to (10), wherein the non-planar surface is the non-planar surface of a refractive optical element, such that the thin optical film and the refractive optical element form a non-planar hybrid thin optical device. (12) The method according to any one of (1) to (10), wherein the non-flat surface is a non-flat surface of a gradient index lens. (13) The method according to any one of (1) to (10), wherein the non-flat surface is the non-flat surface of a helmet visor. (14) An optical device comprising: an optically transparent substrate having a first surface and a second surface for transmitting light through the optically transparent substrate when the light is incident on the optically transparent substrate; and a thin optical film adhered to the first surface of the optically transparent substrate, wherein the thin optical film comprises a thermoplastic material that encapsulates a plurality of surfaces of each of a plurality of patterned features, the plurality of patterned features being disposed within the thermoplastic material to provide at least one optical function to light having at least one specific wavelength that is incident on the thin optical film, and the plurality of patterned features comprising one or both of microscale features and nanometer-scale features. (15) An optical device having the configuration described in (14), wherein the first surface of the optically transparent substrate is non-planar. (16) An optical device having the configuration described in (14) or (15), wherein the optically transparent substrate has a refractive index distribution. (17) An optical device according to any one of (14) to (16), wherein the plurality of patterned features comprises meta-atoms. (18) An optical device according to any one of (14) to (17) in combination with an image source arranged to project an image onto the optical device. (19) The combination of (18), wherein the optically transparent substrate comprises a helmet or goggle visor. (20) An optical device according to any one of (14) to (19) in combination with an imager arranged to record images received from the optical device.

[0098] conclusion While various embodiments of the invention have been described and illustrated herein, those skilled in the art will readily envision various other means and / or structures for performing the functions and / or obtaining one or more of the results and / or advantages described herein, and each such variation and / or modification is deemed to be within the scope of the embodiments of the invention described herein. Furthermore, generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary, and that the actual parameters, dimensions, materials, and / or configurations will depend on the particular application in which the teachings of the invention are used. Those skilled in the art will recognize or be able to ascertain, using no more than routine experimentation, many equivalents to the specific inventive embodiments described herein. Accordingly, the foregoing embodiments are presented by way of example only, and it should be understood that, within the scope of the appended claims and their equivalents, embodiments of the invention may be practiced otherwise than as specifically described and claimed. The inventive embodiments of the present disclosure are directed to each individual feature, system, article, material, kit, and / or method described herein. In addition, any combination of two or more such features, systems, articles, materials, kits, and / or methods is included within the inventive scope of the present disclosure, if such features, systems, articles, materials, kits, and / or methods are not mutually inconsistent.

[0099] Also, various inventive concepts may be embodied as one or more methods, examples of which are provided. Acts performed as part of a method may be ordered in any suitable manner. Thus, embodiments may be constructed to perform acts in an order different from that illustrated, including performing some acts simultaneously despite being shown as sequential acts in the illustrated embodiments.

[0100] All definitions used herein and elsewhere should be understood to control over dictionary definitions, definitions in documents incorporated by reference, and / or ordinary meanings of the defined terms.

[0101] As used herein in the specification and claims, the indefinite articles "a" and "an" should be understood to mean "at least one," unless expressly indicated to the contrary.

[0102] The term "and / or," as used in the specification and claims, should be understood to mean "either or both" of the elements so conjoined, i.e., elements present conjunctively in some cases and disjunctively in other cases. Multiple elements listed with "and / or" should be construed in the same manner, i.e., "one or more" of the elements so conjoined. Other elements, whether related or unrelated to the elements specifically identified by the "and / or" clause, may optionally be present. Thus, as a non-limiting example, a reference to "A and / or B," when used in conjunction with open-ended language such as "comprising," can refer in one embodiment to A only (optionally including elements other than B); in another embodiment to B only (optionally including elements other than A); in yet another embodiment to both A and B (optionally including other elements); etc.

[0103] As used herein and in the claims, "or" should be understood to have the same meaning as "and / or" as defined above. For example, when separating items in a list, "or" or "and / or" shall be interpreted as being inclusive, i.e., including at least one of, but also including two or more of, the several or listed elements and, optionally, additional unlisted items. Terms expressly indicated to the contrary, such as "only one of" or "only one of," or, when used in the claims, "consisting of," only refer to the inclusion of exactly one element of the several or listed elements. In general, the term "or" as used herein shall only be interpreted as indicating exclusive alternatives (i.e., "one or the other, but not both") when preceded by terms of exclusivity, such as "either," "one of," "only one of," or "only one of." As used in the claims, "consisting essentially of" shall have its ordinary meaning as used in the field of patent law.

[0104] As used herein and in the claims, the term "at least one" in connection with a list of one or more elements should be understood to mean at least one element selected from one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed in the list of elements, and not excluding any combination of elements in the list of elements. This definition also allows for the optional presence of elements other than those specifically identified in the list of elements to which the phrase "at least one" refers, whether related or unrelated to the specifically identified element. Thus, as a non-limiting example, "at least one of A and B" (or, equivalently, "at least one of A or B," or, equivalently, "at least one of A and / or B") can refer in one embodiment to at least one, optionally two or more, A, and no B (and optionally including components other than B); in another embodiment to at least one, optionally two or more, B, and no A (and optionally including components other than A); in yet another embodiment to at least one, optionally two or more, A, and at least one, optionally two or more, B (and optionally including other components); etc.

[0105] In the claims and the above specification, all transitional phrases, such as "comprising," "including," "holding," "having," "including," "involving," "holding," "consisting of," etc., are to be understood to be open-ended, i.e., meaning including, but not limited to. Only the transitional phrases "consisting of" and "consisting essentially of" shall be closed or semi-closed transitional phrases, respectively, as defined in the United States Patent Office Manual of Patent Examining Procedures, Section 2111.03.

Claims

1. forming a thin optical element on a planar surface of a first substrate, the thin optical element comprising a plurality of patterned features disposed on the planar surface to provide at least one optical function to light comprising at least one particular wavelength incident on the thin optical element, the plurality of patterned features comprising one or both of microscale features and nanometer-scale features; encasing a plurality of surfaces of each patterned feature of a plurality of patterned features on the planar surface with a thermoplastic material; peeling the thermoplastic material with the plurality of patterned features encapsulated therein from the planar surface to form a thin optical film; applying the thin optical film onto a non-planar surface of a second substrate; A method comprising:

2. 10. The method of claim 1, further comprising the step of pre-distorting a layout pattern of the plurality of patterned features to pre-distort an arrangement of the plurality of patterned features when forming the thin optical element on the planar surface, wherein pre-distorting the layout pattern compensates for distortion of the thin optical film when applied to the non-planar surface.

3. the step of enveloping the plurality of patterned features comprises: spin-coating a solution comprising the thermoplastic material onto the plurality of patterned features; annealing the solution after said spin coating at a temperature above the glass transition temperature of said thermoplastic material; The method of claim 1 , comprising:

4. The method of claim 1 , wherein the plurality of patterned features comprises meta-atoms and the thin optical film is a meta-optic film.

5. The method of claim 1 , wherein the thermoplastic material comprises polyethylene terephthalate glycol (PETG).

6. 10. The method of claim 1, wherein peeling the thermoplastic material comprises etching away a sacrificial layer of material disposed beneath the plurality of patterned features on the first substrate.

7. applying the thin optical film heating the thin optical film; compression molding the thin optical film onto the non-planar surface; The method of claim 1 , comprising:

8. applying the thin optical film heating the thin optical film; applying a vacuum to draw the thin optical film onto the non-planar surface; The method of claim 1 , comprising:

9. The method of claim 8 , wherein the applying a vacuum draws the thin optical film upward against gravity and onto the non-planar surface.

10. the thin optical film is a first thin optical film, 10. The method of claim 1, further comprising laminating the first thin optical film onto the second thin optical film prior to applying the first and second thin optical films to the non-planar surface.

11. The method of claim 1 , wherein the non-planar surface is the non-planar surface of the refractive optical element, such that the thin optical film and refractive optical element form a non-planar hybrid thin optical device.

12. The method of claim 1 , wherein the non-planar surface is a gradient index lens non-planar surface.

13. The method of claim 1 , wherein the non-planar surface is the non-planar surface of a helmet visor.

14. an optically transparent substrate having a first surface and a second surface for transmitting light through the optically transparent substrate when the light is incident on the optically transparent substrate; a thin optical film adhered to a first surface of the optically transparent substrate, the thin optical film comprising: a thin optical film comprising a thermoplastic material encapsulating a plurality of surfaces of each of a plurality of patterned features, the plurality of patterned features being disposed within the thermoplastic material and providing at least one optical function to light comprising at least one particular wavelength incident on the thin optical film, the plurality of patterned features including one or both of microscale features and nanometer-scale features; An optical device comprising:

15. The optical device of claim 14 , wherein the first surface of the optically transparent substrate is non-planar.

16. The optical device of claim 14 , wherein the optically transparent substrate has a refractive index gradient.

17. The optical device of claim 14 , wherein the plurality of patterned features comprises meta-atoms.

18. 15. The optical device of claim 14 in combination with an image source positioned to project an image onto the optical device.

19. 20. The combination of claim 18, wherein the optically transparent substrate comprises a helmet or goggle visor.

20. 15. The optical device of claim 14 in combination with an imager arranged to record images received from the optical device.

Images