Metalens array and display device including same

Abstract

Provided are a metalens array and a display device comprising the same, the metalens array comprising: at least one light-transmitting base layer; a plurality of nanostructures defining one or more metalens arranged in a predetermined array; disposed on the at least one light-transmitting base layer, the nanostructures defining the one or more metalens arranged in a predetermined array; and a thin film coated on the plurality of nanostructures.

Description

[Technical Field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims priority to and incorporates by reference U.S. Patent and Trademark Office (USPTO) U.S. Provisional Application No. 63 / 454,586 filed March 24, 2023, U.S. Provisional Application No. 63 / 439,685 filed January 18, 2023, U.S. Provisional Application No. 63 / 470,167 filed May 31, 2023, U.S. Provisional Application No. 63 / 533,510 filed August 18, 2023, and U.S. Provisional Application No. 18 / 385,717 filed October 31, 2023.

[0002] The present invention relates to the field of optics, and in particular to a metalens array and a display device including the same. Summary of the Invention

[0003] The present application relates to metalens arrays and display devices.

[0004] A first aspect of the present application discloses a metalens array comprising: at least one optically transparent base layer; a plurality of nanostructures disposed on the at least one optically transparent base layer, the nanostructures defining one or more metalenses arranged in a predetermined array; and a thin film coated on the plurality of nanostructures.

[0005] In an embodiment of the first aspect, a metalens array is disclosed, comprising a plurality of nanostructures disposed on at least one optically transparent substrate, the plurality of nanostructures defining one or more metalenses, the one or more metalenses being arranged in a predetermined configuration. The use of overlapping metalens arrays allows light emitted from a microdisplay to be uniformly directed toward a user's eye, overcoming gaps between adjacent lenses and metalens edge defects. Furthermore, application of metalens arrays to head-mounted display systems can address pixelation issues, enabling thinner and lighter systems and improving user experience.

[0006] In one embodiment of the first aspect, the one or more metalenses are arranged so that they do not overlap.

[0007] In one embodiment of the first aspect, the one or more metalenses are arranged so as to overlap.

[0008] In one embodiment of the first aspect, the thin film has a uniform or non-uniform thickness and is applied onto the plurality of nanostructures.

[0009] In one embodiment of the first aspect, the film further comprises a coating layer coated on the thin film.

[0010] In one embodiment of the first aspect, each of the plurality of nanostructures is isotropic, anisotropic, or a combination of isotropic and anisotropic in shape.

[0011] In one embodiment of the first aspect, the nanostructures are of the same shape but arranged in different geometries.

[0012] In one embodiment of the first aspect, said plurality of nanostructures have the same shape but different sizes.

[0013] In one embodiment of the first aspect, the plurality of nanostructures vary in shape and size.

[0014] In an embodiment of the first aspect, the thin film has an optical transmittance greater than an optical transmittance of the plurality of nanostructures.

[0015] A first aspect of the present application discloses a display device comprising: a microdisplay arranged to emit light; and at least one metalens array spaced apart from the microdisplay and configured to transmit light emitted from the microdisplay, wherein the at least one metalens array comprises at least one light-transmitting base layer; a plurality of nanostructures disposed on the at least one light-transmitting base layer, the nanostructures defining one or more metalenses arranged in a predetermined array; and a thin film coated on the plurality of nanostructures.

[0016] In one embodiment of the second aspect, the one or more metalenses are arranged so that they do not overlap.

[0017] In one embodiment of the second aspect, the one or more metalenses are arranged so as to overlap.

[0018] In one embodiment of the second aspect, the thin film has a uniform or non-uniform thickness and is applied onto the plurality of nanostructures.

[0019] In one embodiment of the second aspect, the film further comprises a coating layer coated on the thin film.

[0020] In one embodiment of the second aspect, each of the plurality of nanostructures is isotropic, anisotropic, or a combination of isotropic and anisotropic in shape.

[0021] In one embodiment of the second aspect, the nanostructures are of the same shape but arranged in different geometries.

[0022] In one embodiment of the second aspect, said plurality of nanostructures have the same shape but different sizes.

[0023] In one embodiment of the second aspect, the plurality of nanostructures vary in shape and size.

[0024] In an embodiment of the second aspect, the thin film has an optical transmittance greater than an optical transmittance of the plurality of nanostructures. [Background technology]

[0025] Augmented reality (AR) is a display technology that blends virtual information with the real world. That is, it integrates virtual image information projected by an electronic device based on the real world as seen by the human eye. Conventional head-mounted AR display devices generally include a camera that captures images within the viewer's field of view and projects virtual image information at a default position within the viewer's field of view according to the captured images.

[0026] Metalenses have attracted widespread attention in recent years due to their compactness, efficiency, and large-scale production capabilities. Despite these advantages, metalenses are still far from being commercially viable. Therefore, challenges such as large-area patterning of nanostructures (on the order of centimeter size) and limited material selection, precision, and high-resolution fabrication in the visible spectrum must be thoroughly addressed. Furthermore, high-aspect-ratio dielectric metalenses are the most versatile metasurfaces for manipulating the phase, amplitude, and polarization of light. [Brief explanation of the drawings]

[0027] Many aspects of the present disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present disclosure. Moreover, in the drawings, like reference numerals indicate corresponding parts throughout the several views.

[0028] [Figure 1] 1 is a schematic diagram of a display device according to an embodiment; [Figure 2A] FIG. 1 is a schematic diagram illustrating a configuration (non-polarizer) in which a metalens array according to an embodiment of the present application is applied to a display device. [Figure 2B] FIG. 10 is a schematic diagram illustrating a configuration in which a metalens array according to another embodiment of the present application is applied to a display device (with a polarizer). [Figure 3A] and [Figure 3B] 2C and 2D are side and top views of the metalens array (for four metalenses) shown in FIGS. 2A and 2B in accordance with some embodiments. [Figure 4A] and [Figure 4B] 2C and 2D are side and top views of the metalens array (for one or four metalenses) shown in FIGS. 2A and 2B in accordance with some embodiments. [Figure 5A] , [Figure 5B] and [Figure 5C] FIG. 4C is a schematic diagram of a cell of a passive metalens of the metalens arrays in FIGS. 3A, 3B, 4A, and 4B, in accordance with some embodiments. [Figure 6A] , [Figure 6B] and [Figure 6C] FIG. 4C is a schematic diagram of a cell of a passive metalens of the metalens arrays in FIGS. 3A, 3B, 4A, and 4B, in accordance with some embodiments. [Figure 7A] , [Figure 7B] and [Figure 7C] FIG. 4C is a schematic diagram of a cell of a passive metalens of the metalens arrays in FIGS. 3A, 3B, 4A, and 4B, in accordance with some embodiments. [Figure 8A] , [Figure 8B] and [Figure 8C] FIG. 4C is a schematic diagram of a cell of a passive metalens of the metalens arrays in FIGS. 3A, 3B, 4A, and 4B, in accordance with some embodiments. [Figure 9A] , [Figure 9B] and [Figure 9C] FIG. 4C is a schematic diagram of a cell of a passive metalens of the metalens arrays in FIGS. 3A, 3B, 4A, and 4B, in accordance with some embodiments. [Figure 10A] ~ [Figure 10F] 1 is a plan view of a type of nanostructure, either isotropic or anisotropic. [Figure 11A] ~ [Figure 11D] FIG. 1 is a schematic diagram of a nanofabrication process, according to some embodiments. [Figure 12A] and [Figure 12B] FIG. 10 is a schematic diagram of a cell of a passive metalens of a metalens array comprising nanostructures, according to some embodiments. [Figure 13A] ~ [Figure 13C] FIG. 10 is a plan view illustrating the shape types of cellular nanostructures of a metalens according to some embodiments of the present application. [Figure 14A] ~ [Figure 14C] FIG. 1 is a schematic diagram of a nanofabrication process, according to some embodiments. [Figure 15A] FIG. 1 shows the main results of transmission efficiency for blue, green and red spectra of nanostructures according to one embodiment. [Figure 15B] 1 is a schematic diagram showing the light intensity at the focused point of blue, green, and red light provided in one embodiment. FIG. [Figure 16A] ~ [Figure 16B] , [Figure 17A] ~ [Figure 17B] , [Figure 18A] ~ [Figure 18B] , [Figure 19A] ~ [Figure 19B] and [Figure 20A] ~ [Figure 20B] Some embodiments of the present application provide metalens array cellular nanostructures in which one or more metalenses are configured in different configurations. [Figure 21] FIG. 1 is a schematic diagram illustrating an installation layout of an achromatic metalens, according to one embodiment. [Figure 22] FIG. 10 is a schematic diagram illustrating an arrangement layout of an achromatic metalens in accordance with another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0029] The following disclosure provides many different embodiments or examples for realizing different configurations of the present application. The disclosure is merely exemplary, and modifications may be made to the details within the scope of the principles of the disclosure. All modifications within the meaning and scope of the equivalent elements of the claims are included in the present invention.

[0030] Unless otherwise defined, all technical terms used in this disclosure have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of fully understanding the embodiments described herein, but are not intended to limit the scope of the embodiments.

[0031] The following are some definitions that apply throughout this disclosure:

[0032] The term "coupled" is defined as connected, whether directly or indirectly through intervening elements, and is not necessarily limited to a physical connection. The term "substantially" is defined as essentially conforming to the particular dimensions, shape or other terms that the term modifies, such that elements are not necessarily precise. The term "comprises," when used, means "including, but not necessarily limited to," and specifically denotes open inclusion or membership in combinations, groups, series, etc.

[0033] Augmented reality (AR) is a display technology that blends virtual information with the real world. That is, it integrates virtual image information projected by an electronic device based on the real world as seen by the human eye. Conventional head-mounted AR display devices generally include a camera that captures images within the viewer's field of view and projects virtual image information at a default position within the viewer's field of view according to the captured images.

[0034] 1 shows a lens array applied to a display device in the related art. The display device 9 has a microdisplay and a lens array arranged from the image side to the object side, with a gap or distance between the microdisplay and the lens array. Light emitted from the microdisplay can be transmitted through the lens array to the viewer's eye.

[0035] FIG. 2A shows an embodiment of a metalens array for transmitting or displaying augmented reality (AR), virtual reality (VR), or mixed reality (MR). The metalens array can be applied to display devices such as AR / VR / MR glasses. Display device 90A includes a microdisplay 10, a spacer 51, and a metalens array 30 arranged from the image side to the object side. The microdisplay 10 and the metalens array 30 are uniformly spaced apart by the spacer 51. A light-blocking material 8 is provided on the side of the metalens array 30 away from the microdisplay 10. The microdisplay 10 emits a single light beam and can be used to display a real image that is seen by the user's eyes. However, depending on the design and distance between the microdisplay 10 and the metalens array 30, a real image or a virtual image can be formed as designed. The light beam emitted from the microdisplay 10 may be limited by the light-blocking material 8. In this embodiment, the display device 90A does not require a polarizer (for example, the polarizer 20 shown in FIG. 2B) and a light-transmitting rubber (for example, the light-transmitting rubber 53 shown in FIG. 2B). This is used when the isotropic nanostructure 41 is used.

[0036] FIG. 2B shows a metalens array 30 in which a metalens array is applied to a display device 90B. In at least one embodiment, the display device 90B may be an AR / VR / MR device such as AR / VR / MR glasses. The display device 90B includes a microdisplay 10, a spacer 53, a polarizer 20, a spacer 51, and a metalens array 30, arranged from the image side to the object side. A light-blocking material 8 is provided on the side of the metalens array 30 away from the microdisplay 10. The spacer 53 is located between the microdisplay 10 and the polarizer 20, and the spacer 51 is located between the polarizer 20 and the metalens array 30. In at least one embodiment, the polarizer 20 may be a linear polarizer, a circular polarizer, or a combination of a linear polarizer and a quarter-wave plate. In one embodiment, the polarizer 20 is a circular polarizer that circularly polarizes light emitted by the microdisplay 10. In other embodiments, the polarizer 20 may be a linear polarizer or a combination of a linear polarizer and a quarter-wave plate. In at least one embodiment, the polarizer 20 may be bonded to the microdisplay 10 via a transparent optical rubber 53, i.e., the spacer 53 may be formed from a transparent optical rubber. The light flux emitted from the microdisplay 10 may be restricted by a light blocking material 8. A polarizer-dependent scheme is used when operating on a geometric phase principle or other principle that allows light emitted from the microdisplay 10 to be completely manipulated by a 2π phase transition using anisotropic nanostructures 41. In one embodiment, the display device 90A, 90B includes a microdisplay 10 and at least one metalens array 30. The microdisplay 10 is positioned to emit light. The at least one metalens array 30 is spaced from the microdisplay 10. The at least one metalens array 30 is positioned to transmit light emitted by the microdisplay 10.

[0037] 3A and 3B are side and top views of metalens array 30 (for four metalenses) shown in FIGS. 2A and 2B. Metalens array 30 includes at least one optically transparent substrate layer 42 and a plurality of nanostructures 41. Optically transparent substrate 42 may be any type of transparent substrate, such as, for example, glass made from fused silicon (SiO) or sapphire, or a reflective member made from silicon or other materials.

[0038] 3A and 3B, region 40 is an enlarged representation of one or more metalenses 35. A plurality of nanostructures 41 are disposed on or fabricated on an optically transparent base layer 42. The plurality of nanostructures 41 are disposed to define or form one or more metalenses 35, for example, the four metalenses 35 shown in FIGS. 3A and 3B is not intended to be limiting of the present application. The plurality of nanostructures 41 may form a metasurface in the metalens array 30. In at least one embodiment, the plurality of nanostructures 41 may be arranged in any arrangement, such as a grid, row, or column, in the plurality of metalens arrays 30. In at least one embodiment, the plurality of nanostructures 41 may be comprised of materials such as dielectrics, such as curable resins, photoresists, metal oxide nanoparticles, and sol-gel mixtures, nanopillars ranging in thickness from 150 nanometers (nm) to several thousand nanometers, and thin deposits of metal oxides (TiO2, Al2O3, HfO2) or metals (e.g., gold, silver, aluminum) ranging in thickness from 10 to 70 nm, although the present application is not limited to these numerical ranges. In at least one embodiment, the plurality of nanostructures 41 may be formed from materials such as nanoimprinted resins.

[0039] In at least one embodiment, the diameter of each metalens 35 in metalens array 30 may vary. In at least one embodiment, the outline of each metalens 35 may be rectangular (as shown in FIG. 3A ), circular (as shown in FIG. 3B ), or any shape depending on the shape of the display device.

[0040] A thin film 43 is applied over the plurality of nanostructures 41. In at least one embodiment, an atomic layer deposition system is used to conformally deposit the thin film 43 over the patterned resin of the plurality of nanostructures 41. The thin film 43 is made of TiO2, Al2O3, HfO2, or the like. That is, in at least one embodiment, the thin film 43 has a conformal thickness applied over the plurality of nanostructures 41. In another embodiment, the thin film 43 has a non-conformal thickness applied over the plurality of nanostructures 41.

[0041] In at least one embodiment, the material of the plurality of nanostructures 41 comprises a dielectric material (TiO2, Al2O3, HfO2) or a metal (gold, silver, aluminum, etc.) and a nanoimprint resin.

[0042] Figure 4A shows at least one embodiment of a side view and a top view of a single lens of metalens array 30 shown in Figure 2A or 2B. As shown in Figure 4A, multiple nanostructures 41 can form a single metalens 35 having a larger size.

[0043] FIG. 4B illustrates at least one embodiment of a side view and a top view of the lens array of the metalens array 30 shown in FIG. 2A or 2B. As shown in FIG. 4B, the plurality of nanostructures 41 can form a lens array of the metalens array 30 that includes four metalenses 35. Every two adjacent metalenses 35 partially overlap, i.e., the edges of every two adjacent metalenses 35 overlap. In one embodiment, one or more metalenses 35 are arranged so that they do not overlap, as shown in FIGS. 3A, 3B, and 4A. In other embodiments, one or more metalenses 35 are arranged so that they overlap, as shown in FIG. 4B.

[0044] FIG. 5A shows an example of at least one cell 401 of the metalens array 30 of FIGS. 3A, 3B, and 4A, 4B. The metalens array 30 may be divided into a plurality of cells, such as cell 401. As shown in FIG. 5A, cell 401 includes a cylindrical nanostructure 41. The cell 401 includes nanostructures 41, whose dimensions include an inner diameter (radius of the resin) D, an outer diameter D+2*t (resin or thin film 43 coated with a high refractive index material), a thickness t of the conformal deposited material or a thickness t of the deposited thin film, and a height H of the resin (resist), where H is the remaining resin after nanoimprinting, designated 41R, or nanostructure 41, designated as nanostructure layer 41R, and the thin film material is designated 43. In at least one embodiment, the thin film 43 is uniformly coated on the nanostructures 41 and the nanostructure layer 41R, i.e., the thickness of the thin film 43 is uniform, as shown in Figures 5A, 5B, and 5C. The cell 401 includes one base layer 42, the dimensions of which are represented by a pitch Px (along the x-direction) and a pitch Py (along the y-direction).

[0045] Figure 5B shows at least one embodiment of a cell 402 of the metalens array 30 of Figures 3A, 3B and 4A, 4B. The metalens array 30 may be divided into a plurality of cells, such as cell 402. As shown in Figure 5B, cell 402 includes one rectangular nanostructure 41. Cell 402 includes nanostructure 41 and has dimensions of an inner width W, an outer width W+2*t, an inner length L, an outer length L+2*t, and a resin (resist) height H, where H R is the height of the remaining resin (denoted as 41R or named nanostructure layer 41R) after nanoimprinting. The cell 402 has one base layer 42, whose dimensions are represented by a pitch Px (along the x-direction) and a pitch Py (along the y-direction). The thin film 43 is made of a high refractive index material such as TiO2, Al2O3, or HfO2, and is conformally deposited on the patterned resin (nanostructure) 41 using an atomic layer deposition system.

[0046] 5A and 5B, showing details of the nanostructure 41, the substrate 42, and the thin film 43. As shown in FIG. 5C, t is the thickness of the thin film 43, H is the height of the nanostructure 41, and H R is the thickness of the nanostructure layer 41R, and the nanostructure 41 is provided on the base layer 42.

[0047] FIG. 6A illustrates an example of a cell 403 of the metalens array 30 of FIGS. 3A, 3B, and 4A, 4B. FIG. 6A corresponds to FIG. 5A in which the thickness of the thin film 43 (which may be a high refractive index material) is non-uniform on the nanostructure 41 made of resin or resistor. t1, t2, and t3 represent the thicknesses of the thin film 43 on the top, sides, and bottom of the nanostructure 41, respectively. In at least one example, t1, t2, and t3 are different from one another, i.e., t1 ≠ t3 ≠ t2. In other examples, t1 = t3 ≠ t2. In other examples, t1 = t2 ≠ t3.

[0048] FIG. 6B shows an example of a cell 404 of the metalens array 30 of FIGS. 3A, 3B, and 4A, 4B. FIG. 6B corresponds to FIG. 5B in the case where the thickness of the thin film 43 (which may be a high refractive index material) on the nanostructure 41 made of resin or resistor is not uniform. t1, t2, and t3 represent the thicknesses of the thin film 43 on the top, sides, and bottom of the nanostructure 41, respectively. In other words, t1, t2, and t3 are different from one another, i.e., t1 ≠ t3 ≠ t2.

[0049] Figure 6C shows a cross-sectional view of cells 303, 404 of the metalens array 30 of Figures 6A and 6B. Figure 6C corresponds to Figure 5C in the case where the thickness of thin film 43 (which may be a high refractive index material) on nanostructures 41 made of resin or resistor is not uniform. In other words, t1, t2, and t3 are different from one another, i.e., t1 ≠ t3 ≠ t2.

[0050] FIG. 7A shows an example of a cell 405 of the metalens array 30 of FIGS. 3A, 3B, and 4A, 4B. The cell 405 includes a cylindrical nanostructure 41. The cell 405 includes nanostructures 41, and the dimensions of the nanostructures 41 are an inner diameter (radius of the resin) D, an outer diameter D+2*t2 (resin or thin film 43 coated with a high refractive index material), and a thickness t of the conformal deposited material or deposited thin film, which is not uniform throughout the nanostructure 41. t1, t2, and t3 represent the thicknesses of the thin film 43 at the top, sides, and bottom of the nanostructure 41, respectively. The height H of the resin (resist) is, in this example, void of any remaining resin. The cell 405 includes one base layer 42, and the dimensions of the base layer 42 are represented by a pitch Px (along the x-direction) and a pitch Py (along the y-direction).

[0051] FIG. 7B shows an example of a cell 406 of the metalens array 30 of FIGS. 3A, 3B, and 4A, 4B. The cell 406 includes a rectangular nanostructure 41. The cell 406 includes nanostructures 41 with dimensions including an inner width W, an outer width W+2*t2, an inner length L, an outer length L+2*t2, and a height H of the resin (resist), where the resin and the base layer 42, whose dimensions are represented by a pitch Px (along the x-direction) and a pitch Py (along the y-direction), remain. A thin film 43 made of a high refractive index material such as TiO2, Al2O3, or HfO2 is conformally deposited on the patterned resin (nanostructure) 41 using an atomic layer deposition system.

[0052] 7A and 7B, showing the detailed sizes of the nanostructures 41, the base layer 42, and the thin film 43. As shown in FIG. 7C, t1, t2, and t3 represent the thicknesses of the thin film 43 on the top, sides, and bottom of the nanostructures 41, respectively, and H is the height of the nanostructures 41, where the nanostructures 41 are disposed on the base layer 42.

[0053] Figure 8A shows at least one embodiment of a cell 407 of the metalens array 30 of Figures 3A, 3B and 4A, 4B. Figure 8A corresponds to Figure 7A, and illustrates an example in which the thickness of the cladding layer 44 is H clad The only difference is that the thin film 43 has a cover layer 44 that may be spin-coated (or evaporated) onto it. The cover layer 44 may be an impedance matching layer. The refractive index of the cover layer 44 may be close to that of the base layer 42. The cover layer 44 may be made of SiO2, resin, photoresist, etc.

[0054] Figure 8B illustrates at least one embodiment of a cell 408 of the metalens array 30 of Figures 3A, 3B and 4A, 4B. Figure 8B corresponds to Figure 7B, and illustrates an example in which the thickness of the cladding layer 44 is H cladThe only difference is that the thin film 43 has a cover layer 44 that may be spin-coated (or evaporated) onto it. The cover layer 44 may be an impedance matching layer. The refractive index of the cover layer 44 may be close to that of the base layer 42. The cover layer 44 may be made of SiO2, resin, photoresist, etc.

[0055] FIG. 8C corresponds to FIG. 7C, and shows a case where the thickness of the coating layer 44 is H clad The only difference is that the thin film 43 has a cover layer 44 spin-coated (or evaporated) on it. The cover layer 44 may be an impedance matching layer. The refractive index of the cover layer 44 may be close to the refractive index of the base layer 42. The cover layer 44 may be formed of SiO2, resin, photoresist, or the like. In at least one embodiment, the cover layer 44 covers the thin film 43 shown in Figures 5A-5B, 6A-6C, and 7A-7C.

[0056] Figure 9A shows an example of a cell 409 of the metalens array 30 of Figures 3A, 3B and 4A, 4B. Figure 9A corresponds to Figure 6A, i.e., the impedance matching layer, labeled cladding layer 44, has a thickness of H clad The only difference is that the refractive index of the cover layer 44 may be close to the refractive index of the base layer 42. The cover layer 44 may be spin-coated (or evaporated) onto the thin film 43. The cover layer 44 may be formed from SiO2, resin, photoresist, or the like.

[0057] Figure 9B shows an example of a cell 410 of the metalens array 30 of Figures 3A, 3B and 4A, 4B. Figure 10B corresponds to Figure 6B and shows an example of an impedance matching layer, labeled cladding layer 44, with a thickness of H clad The only difference is that the refractive index of the cover layer 44 may be close to the refractive index of the base layer 42. The cover layer 44 may be spin-coated (or evaporated) onto the thin film 43. The cover layer 44 may be formed from SiO2, resin, photoresist, or the like.

[0058] FIG. 9C corresponds to FIG. 6C, and shows an impedance matching layer having a thickness of Hclad The only difference is that the refractive index of the cover layer 44 may be close to the refractive index of the base layer 42. The cover layer 44 may be spin-coated (or evaporated) onto the thin film 43. The cover layer 44 may be formed from SiO2, resin, photoresist, or the like.

[0059] As shown in Figures 5A-5C, in one embodiment, thin film 43 has a uniform thickness and is applied over the plurality of nanostructures 41. In other embodiments, thin film 43 has a non-uniform thickness and is applied over the plurality of nanostructures 41, as shown in Figures 6A-6C, 7A-7C, 8A-8C, and 9A-9C.

[0060] It will be understood that Figures 5A, 5B, 5C, 6A, 6B, 6C, 7A, 7B, 7C, 8A, 8B, 8C, 9A, 9B, and 9C illustrate at least one cell of a passive metalens in the metalens array 30 shown in Figures 3A, 3B, 4A, and 4B. It will be understood that a plurality of cells (e.g., cells 401, 402, 403, 404, 405, 406, 407, 408, 409, 410 shown in Figures 5A, 5B, 5C, 6A, 6B, 6C, 7A, 7B, 7C, 8A, 8B, 8C, 9A, 9B, and 9C) make up a metalens 35, and a plurality of metalenses 35 make up the metalens array 30. Alternatively, the metalens array 30 may include an arrangement of a plurality of metalenses 35, each formed from a plurality of cells (e.g., cells 401, 402, 403, 404, 405, 406, 407, 408, 409, and 410 shown in Figures 5A, 5B, 5C, 6A, 6B, 6C, 7A, 7B, 7C, 8A, 8B, 8C, 9A, 9B, and 9C).

[0061] In some embodiments, the cells of metalens array 30 may be the same size or may have different sizes. For example, three or more different cells may be used, but the same height is required for all colors because the pitch, width, and length may be different for each color. However, in one particular embodiment, the same cells (same pitch) may be used for all colors (different widths and lengths, but the same height).

[0062] In at least one embodiment, the optical transmittance of the thin film 43 is greater than the optical transmittance of the plurality of nanostructures 41 .

[0063] The nanostructures 41 may be formed in different isotropic, anisotropic, or a combination of isotropic and anisotropic shapes, depending on the desired spectrum and the degree of phase and amplitude modulation. FIGS. 10A-10F show examples of top views of nanostructures 41 of different types or cross-shaped configurations. FIGS. 10A-10F illustrate different shape types of the cross-sections of the cells of FIGS. 5A, 5B, 6A, 6B, 7A, 7B, 8A, 8B, 9A, and 9B. Each of the nanostructures 41 may be generally circular as shown in FIG. 10A, generally triangular or square as shown in FIG. 10B, generally rectangular as shown in FIG. 10C, or anisotropic as shown in FIGS. 10D, 10E, and 10F. According to one embodiment, as shown in FIGS. 5A, 6A, 7A, 8A, and 9A, one of the plurality of nanostructures 41 has a circular shape. In another embodiment, the plurality of nanostructures 41 may have other shapes, such as an "L" shape or an "H" shape; the present disclosure is not limited thereto. Each of the plurality of nanostructures 41 is spaced apart at a pitch Px in the X direction and a pitch Py in the Y direction, where Px is 150 nm to 700 nm and Py is 150 nm to 700 nm. The pitch is defined in two ways: center-to-center between two adjacent nanostructures or edge-to-edge between two adjacent nanostructures. Each of the plurality of cellular nanostructures 41 may have a diameter D of 40 nm to 500 nm. Each of the plurality of cellular nanostructures 41 may have a height H of 150 nm to 3000 nm. However, these values ​​may differ in anisotropic nanostructures.

[0064] For example, an isotropic shape may be circular, rectangular, or have the same dimensions when viewed from either side. For example, an anisotropic shape may be rectangular, an "L", an "H", or any shape that has different dimensions when viewed from different sides.

[0065] Figure 11A shows a schematic of the EBL nanofabrication process requiring hard mask deposition and etching. The fabrication sequence, from left to right, is as follows:

[0066] Step 1 deposits a high-refractive index dielectric material (TiO, GaN, SiN, Si, etc.) on a transparent wafer (e.g., fused silica and sapphire) labeled as base layer 42 in Figures 3A-3B, 4A-4B, 5A-5C, 6A-6C, 7A-7C, 8A-8C, and 9A-9C (an intermediate layer shown in a spin-coating process).

[0067] Step 2 involves applying a thin layer of adhesive film (not shown), a layer of photoresist (e.g., as the top layer shown in the spin-coating process), and a final layer of conductive polymer (not shown) to avoid charging issues in the subsequent EBL process.

[0068] The exposure step involves exposing the top layer using a high-accelerating voltage EBL to create the metalens, followed by removing the conductive polymer layer in deionized water and developing the exposed resist in a compatible photo-resist developer, respectively.

[0069] The hard mask step involves depositing a relatively thin metal (nickel, chromium, etc.) film as a hard mask on the developed resist.

[0070] The lift-off step removes the photoresist using a photoresist solvent such as acetone or remover PG.

[0071] The etching step etches the high refractive index dielectric material by reactive ion etching.

[0072] The hard mask removal step is the final step, in which the hard mask layer is dissolved in an acid-based solution to leave only the patterned dielectric nanostructures.

[0073] Figure 11B shows a schematic diagram of the nanofabrication process using EBL, DUV, and EUV. This requires a thick, high-quality atomic deposition layer. The fabrication sequence, from left to right, is as follows:

[0074] Step 1 involves applying a thin layer of adhesive film (not shown), a layer of photoresist (as the top layer shown in the spin coating process), and a final layer of conductive polymer (not shown) onto a transparent wafer (e.g., fused silica and sapphire), designated as base layer 42 in Figures 3A-3B, 4A-4B, 5A-5C, 6A-6C, 7A-7C, 8A-8C, and 9A-9C, to avoid charging issues in the subsequent EBL process.

[0075] The exposure step involves exposing the top layer using high accelerating voltage EBL, DUV, or EUV to create the metalens, followed by developing the exposed resist in a compatible resist developer (if EBL is used, the conductive polymer layer is removed in deionized water).

[0076] The deposition step then uses low-temperature atomic layer deposition (LTALD) to conformally deposit a thin film of a high refractive index material such as TiO2, Al2O3, or HfO2 onto the developed resin, completely depositing the thin film onto the patterned resist nanostructures until the gaps between the nanostructures are completely filled.

[0077] The final etching step involves removing the excess TiO2 thin film using reactive ion etching and an appropriate etching gas until the underlying resist layer is revealed.

[0078] The stripping step involves removing the photoresist using a photoresist solvent (acetone, remover PG, etc.).

[0079] Figure 11C shows a schematic diagram of a typical nanofabrication process comprising NIL hardmask deposition and etching, with the fabrication sequence from left to right as follows:

[0080] The stamping step involves creating a master stamp on a silicon-based substrate using high-accelerating voltage EBL, then creating a working stamp. When a high-modulus silicone elastomer film is cast onto the master stamp and thermally cured, the working stamp is a replica of the master stamper, placed face-down in the thermally cured silicone elastomer, with glass on its backside.

[0081] In the hard mask step, a single-layer or multi-layer (not shown) hard mask made of Au, Cr, SiO 2 or the like is deposited on the processing stamp under high vacuum conditions.

[0082] The downturned step involves transferring a hard mask onto a transparent wafer such as fused silica or sapphire, and spin-coating an adhesion layer on top of a high-index material such as TiO2 (or GaN, polysilicon, etc.).

[0083] In the release step, after transferring the hard mask onto the substrate, the TiO2 layer is etched using a chromium (Cr) layer to release the processing stamp.

[0084] The etching step continues to etch the TiO2 until the transparent substrate is exposed.

[0085] The residual removal step involves removing the chromium (Cr) layer using an etchant after the etching step. Finally, the residual layer above the TiO metalens is dissolved by the etching solution.

[0086] Figure 11D shows a schematic diagram of the direct NIL nanofabrication process using metal oxide nanoparticles and a sol-gel mixture instead of resin. Replicas of the master stamp can also be fabricated using water-soluble polymers such as hard polydimethylsiloxane (h-PDMS) and polyvinyl alcohol (PVA).

[0087] The manufacturing sequence is as follows from left to right:

[0088] The stamping step involves creating a master stamp on a silicon-based substrate using high-accelerating voltage EBL, then creating a working stamp. When a high-modulus silicone elastomer film is cast onto the master stamp and thermally cured, the working stamp is a replica of the master stamper, placed face-down in the thermally cured silicone elastomer, with glass on its backside.

[0089] In the spin-coating step, an inorganic film is spin-coated onto a transparent substrate such as glass or sapphire using a metal oxide nanoparticle-based ink, for example, a TiO2-based nanoparticle ink.

[0090] In the pressing step, a processing stamp is placed on the spin-coated wafer and pressure is applied.

[0091] The curing step involves UV folding the film into the holes and grooves of the processing stamp.

[0092] A demolding step finally releases the fabrication stamp to form hardened nanostructures.

[0093] The table below lists common and novel nanofabrication techniques. The advantages and disadvantages of these methods are also listed in the table. While each of these techniques solves one or two problems, they still present other challenges. Therefore, a new nanofabrication process is needed that addresses the cost, time, ease of fabrication, and efficiency of metalenses. This application presents a novel nanofabrication technique, as shown in Figure 14. After the fabrication stamp is released, a thin deposition of a high-refractive-index dielectric (TiO2, Al2O3, HfO2) or metal (e.g., gold, silver, aluminum, etc.) is required, with a thickness of 10 nm to 70 nm. Atomic layer deposition is preferred for depositing high-refractive-index dielectric materials.

[0094] [Table 1]

[0095] Figure 12A shows a cell with nanostructures consisting of perfectly vertical sidewalls, as shown on the left side of Figure 12A, and tapered sidewalls, as shown on the right side of Figure 12A. As shown in Figure 12A, the nanostructure sidewalls are tapered. A single supercell can have multiple nanostructures that commonly provide the phase needed to manipulate optical properties such as polarization and amplitude. This significantly reduces efficiency because it cannot satisfy the phase slope required for complete control of the incident light.

[0096] Figure 12B shows how tapered nanostructures cannot meet the phase coverage (2π) required to fully manipulate light, whereas supercells with perfect sidewalls can fully meet the 2π phase change and maintain high efficiency.

[0097] FIGS. 13A-13C illustrate top view types of cell nanostructures 42, 82 for metalenses. FIG. 13A shows a schematic diagram of the Pancharatnam-Berry (PB) phase, or geometric phase, required for anisotropic nanostructures. A multi-cell nanostructure is shown in FIG. 13A. FIG. 13A illustrates a shape that is fully anisotropic and may be polarizer-dependent. For example, the anisotropic shape may be a rectangle, an "L," an "H," or any shape with different dimensions when viewed from different sides. As shown in FIG. 13A, the darker shapes represent multiple anisotropic nanostructures. As shown in FIG. 13A, a square represents one cell of the nanostructure 41. In some embodiments, the multiple nanostructures 41 shown in FIG. 13A may be disposed on a base layer 42.

[0098] FIG. 13B shows a schematic diagram of the propagation phase of isotropic nanostructures of different sizes. The multiple cell nanostructures in FIG. 13B have a completely isotropic shape and are polarizer-independent. The isotropic shape can be any isotropic shape, such as a circle or a square, and has the same size when viewed from either side. The dark shapes represent multiple isotropic nanostructures. Each circle represents one unit cell of the nanostructure 41, as shown in FIGS. 10A-10F and 13A-13C. In some embodiments, the multiple nanostructures 41 shown in FIG. 13B may be disposed on a base layer 42.

[0099] Figure 13C shows a general form of a combined design of propagation phase and PB phase using a dispersion-engineered library of different nanostructure shapes. In some embodiments, the nanostructures 41 shown in Figure 13C may be disposed on a substrate 42. The shape of the multi-cell nanostructures shown in Figure 13C may be a combination of the types described above (i.e., a combination of isotropic and anisotropic shapes), and the multi-cell nanostructures may be polarizer dependent.

[0100] In one embodiment, the nanostructures 41 have the same shape but different arrangements, as shown in Figure 13A. In one embodiment, the nanostructures 41 have the same shape but different sizes, as shown in Figure 13B. In another embodiment, the nanostructures 41 have different shapes and different sizes, as shown in Figure 13C.

[0101] FIG. 14A is a schematic diagram of the nanofabrication process for the finally proposed etching-free EBL, DUV, and EUV technologies. As shown in the left diagram of FIG. 14A, a photoresist (or resin) is developed on a base layer (base layer 42 shown in FIGS. 3A-3B, 4A-4B, 5A-5C, 6A-6C, 7A-7C, 8A-8C, and 9A-9C). Next, as shown in the right diagram of FIG. 14A, a metal oxide thin film (TiO2, Al2O3, HfO2) or a metal (e.g., gold, silver, aluminum, etc.) is deposited on the photoresist (or resin).

[0102] Figure 14B shows a schematic diagram of the final proposed etch-free nanofabrication process for the NIL technology. As shown in the left panel of Figure 14B, photoresist (or resin) is cured on the base layer 42 shown in Figures 3A-3B, 4A-4B, 5A-5C, 6A-6C, 7A-7C, 8A-8C, and 9A-9C. The work stamp is then released (left panel), and a thin metal oxide film (TiO2, Al2O3, HfO2) or metal (e.g., gold, silver, aluminum, etc.) is deposited on the resin (right panel). In this example, a residual layer of resin may remain on the base layer, as shown in Figure 14B.

[0103] Figure 14C is a schematic diagram of the final proposed nanofabrication process for the etch-free NIL technology. As shown in the left panel of Figure 14C, photoresist (or resin) is cured on the base layer, and the work stamp is released. Next, a metal oxide thin film (TiO2, Al2O3, HfO2) or metal (gold, silver, aluminum, etc.) is deposited on the base layer 42 shown in Figures 3A-3B, 4A-4B, 5A-5C, 6A-6C, 7A-7C, 8A-8C, and 9A-9C, and on the resin shown in the right panel of Figure 14C. In this example, no residual layer of resin remains on the base layer, as shown in Figure 14C.

[0104] FIG. 15A shows the main results of the focusing efficiency of the provided nanostructures in the blue, green, and red spectra.

[0105] Figure 15B shows the light intensity of blue (470 nm), green (530 nm), and red (632 nm) at the focal point. As shown in Figure 15B, the focusing results of the achromatic metalenses shown in Figure 21 are shown when three different types of nanostructures are employed, but the method described in Figure 22 may also be used.

[0106] Figure 16A shows several example metalenses 35 of a metalens array 30, each of which is rectangular in shape. The nanostructures 41 can be any of the nanostructures shown in Figures 10A-10F and 13A-13C. According to one example, a plurality of cell nanostructures 41 can be arranged as a plurality of rectangular metalenses 35 to form the metalens array 30 shown in Figure 16A.

[0107] Figure 16B shows several embodiments of metalens 35 presented in the form of a large rectangular single metalens 35. The nanostructures 41 can be any of the nanostructures shown in Figures 10A-10F and 13A-13C. As shown in Figure 16B, according to one embodiment, a plurality of cellular nanostructures 41 can be arranged into a single large rectangular metalens.

[0108] Figure 17A shows several example metalenses 35 of a metalens array 30, each of which has a circular shape. The nanostructures 41 can be any of the nanostructures shown in Figures 10A-10F and 13A-13C. According to one example, a plurality of cell nanostructures 41 can be arranged as a plurality of circular metalenses 35 to form the metalens array 30 shown in Figure 17A.

[0109] Figure 17B shows an example of a metalens 35 that is a large circular single-unit metalens 35. The nanostructures 41 can be any of the nanostructures shown in Figures 10A-10F and 13A-13C. According to one example, multiple cellular nanostructures 41 can be arranged in a single circular metalens 35, and the metalens 35 can be larger in size as shown in Figure 17B.

[0110] 18A and 18B show several example metalenses 35 of a metalens array 30, which may have irregular shapes and be positioned in different locations. The nanostructures 41 may be any of the nanostructures shown in FIGS. 10A-10F and 13A-13C. According to one example, a plurality of cellular nanostructures 41 may be arranged as a plurality of metalenses 35, and the plurality of metalenses 35 may be arranged in an irregular shape and positioned in different locations to form a metalens array 30 such as that shown in FIGS. 18A and 18B.

[0111] 19A and 19B show one embodiment of the proposed metalens 35, which can be arranged in different locations as a single irregularly shaped metalens 35. The nanostructures 41 can be any of the nanostructures shown in FIGS. 10A-10F and 13A-13C. Referring to FIGS. 19A and 19B, according to one embodiment, a single metalens 35 can have multiple cellular nanostructures 41 arranged, and the metalenses 35 can be arranged in different locations to form an irregular shape.

[0112] 20A and 20B show several embodiments using metalens arrays 30 with different arrangements of overlapping metalens 35. The nanostructures 41 may be any of the nanostructures shown in FIGS. 10A-10F and 13A-13C. As shown in FIGS. 20A and 20B, according to one embodiment, a plurality of cellular nanostructures 41 are arranged as a plurality of metalenses 35, and the multiple metalenses 35 may be arranged in different overlapping arrangements to form different metalens arrays 30.

[0113] In at least one embodiment, in Figures 16A, 16B, 17A, 17B, 18A, 18B, 19A, 19B, 20A, and 20B, cell 411 may be any of cells 401, 402, 403, 404, 405, 401, 402, 403, 404, 405, 406, 407, 408, 409, and 410 shown in Figures 5A, 5B, 5C, 6A, 6B, 6C, 7A, 7B, 7C, 8A, 8B, 8C, 9A, 9B, and 9C.

[0114] Figure 21 shows the layout design of an achromatic metalens. To obtain a three-color achromatic metalens, at least three different nanostructures are required, unless there is spectral overlap between the bands of one or two nanostructures, such as the nanostructures shown in Figures 13A and 13C. As shown in FIG. 21 , nanostructure 41B in the cells shown in FIGS. 5A, 5B, 5C, 6A, 6B, 6C, 7A, 7B, 7C, 8A, 8B, 8C, 9A, 9B, and 9C corresponds to the shortest wavelength (e.g., for blue), nanostructure 41G shown in FIGS. 5A, 5B, 5C, 6A, 6B, 6C, 7A, 7B, 7C, 8A, 8B, 8C, 9A, 9B, and 9C corresponds to the medium wavelength (e.g., for green), and nanostructure 41R shown in FIGS. 5A, 5B, 5C, 6A, 6B, 6C, 7A, 7B, 7C, 8A, 8B, 8C, 9A, 9B, and 9C corresponds to the longest wavelength (e.g., for red). The pitch dimensions (Px and Py) of the plurality of nanostructures 41B, 41G, and 41R may be similar or different. B , N G , and N R is the number of cells of each color, and each color may be different or similar to the other colors. For example, N B = N G = N R= 4, each step of the circular metalens is four rings, blue, green, and red, and these rings are repeated in the same order to the edge of the lens. In this example, a set of four-ring nanostructures 41B is located in the inner ring region, a set of four-ring nanostructures 41G is located in the middle ring region, and a set of four-ring nanostructures 41R is located in the outer ring region. In another example, a set of two-ring nanostructures 41B is located in the inner ring region, a set of three-ring nanostructures 41G is located in the middle ring region, and a set of four-ring nanostructures 41R is located in the outer ring region. NB, NG, and NR can be any integers. Nanostructures 41B, nanostructures 41G, and nanostructures 41R all have the same height.

[0115] Figure 22 shows another layout design for an achromatic metalens. To obtain a three-color achromatic metalens, at least three different nanostructures should be present, unless there is spectral overlap between the bands of one or two of the nanostructures, such as the nanostructures shown in Figures 13A and 13C. Nanostructure 41B in the cells shown in Figures 5A, 5B, 5C, 6A, 6B, 6C, 7A, 7B, 7C, 8A, 8B, 8C, 9A, 9B and 9C corresponds to the shortest wavelength (e.g., for blue), nanostructure 41G shown in Figures 5A, 5B, 5C, 6A, 6B, 6C, 7A, 7B, 7C, 8A, 8B, 8C, 9A, 9B and 9C corresponds to the medium wavelength (e.g., for green), and nanostructure 41R shown in Figures 5A, 5B, 5C, 6A, 6B, 6C, 7A, 7B, 7C, 8A, 8B, 8C, 9A, 9B and 9C corresponds to the longest wavelength (e.g., for red). The pitch dimensions (Px and Py) of the multiple nanostructures 41B, 41G, and 41R may be similar or different. Figure 22 shows one arrangement of the nanostructures 41B, 41G, and 41R. The nanostructures 41B, 41G, and 41R may be arranged in any manner. The heights of the nanostructures 41B, 41G, and 41R are all the same.

[0116] It should be noted that any steps and any technical features in the above embodiments of the present application can be freely combined in any way, and therefore, those skilled in the art can make various modifications to the embodiments without departing from the scope of the present disclosure as defined by the appended claims.

Claims

1. at least one optically transparent substrate; a plurality of nanostructures disposed on the at least one optically transparent substrate, the nanostructures defining one or more metalenses arranged in a predetermined array; a thin film applied over the plurality of nanostructures.

2. 10. The metalens array of claim 1, wherein the one or more metalens are arranged so that they do not overlap.

3. 10. The metalens array of claim 1, wherein the one or more metalenses are arranged so as to overlap.

4. 10. The metalens array of claim 1, wherein the thin film has a uniform or non-uniform thickness and is applied over the plurality of nanostructures.

5. 10. The metalens array of claim 1, further comprising a coating layer coated on top of the thin film.

6. 10. The metalens array of claim 1, wherein each of the plurality of nanostructures is isotropic, anisotropic, or a combination of isotropic and anisotropic in shape.

7. 10. The metalens array of claim 1, wherein the plurality of nanostructures have the same shape but are arranged in different geometric topologies.

8. 10. The metalens array of claim 1, wherein the plurality of nanostructures have the same shape but different sizes.

9. 10. The metalens array of claim 1, wherein the plurality of nanostructures vary in shape and size.

10. 10. The metalens array of claim 1, wherein the optical transmittance of the thin film is greater than the optical transmittance of the plurality of nanostructures.

11. a microdisplay arranged to emit light; at least one metalens array spaced apart from the microdisplay and configured to transmit light emitted from the microdisplay; the at least one metalens array at least one optically transparent substrate; a plurality of nanostructures disposed on the at least one optically transparent substrate, the nanostructures defining one or more metalenses arranged in a predetermined array; a thin film applied onto the plurality of nanostructures.

12. 12. The display of claim 11, wherein the one or more metalenses are arranged so that they do not overlap.

13. 12. The display device of claim 11, wherein the one or more metalenses are arranged so as to overlap.

14. The display device of claim 11, wherein the thin film has a uniform or non-uniform thickness and is applied onto the plurality of nanostructures.

15. The display device according to claim 11 , further comprising a covering layer covering the thin film.

16. The display device of claim 11 , wherein each of the plurality of nanostructures has an isotropic, an anisotropic, or a combination of an isotropic and anisotropic shape.

17. The display device of claim 11 , wherein the plurality of nanostructures have the same shape but are arranged in different geometric topologies.

18. The display device of claim 11 , wherein the plurality of nanostructures have the same shape but different sizes.

19. The display device of claim 11 , wherein the plurality of nanostructures have different shapes and sizes.

20. The display device of claim 11 , wherein the thin film has a light transmittance greater than that of the plurality of nanostructures.

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