Optical element based on a polymer structure incorporating an inorganic material

Abstract

The present disclosure relates to display systems, and more particularly, to augmented reality display systems. In one aspect, a method of fabricating an optical element includes providing a substrate having a first refractive index and being transparent in the visible spectrum. The method further includes forming a periodically repeating polymer structure on the substrate. The method further includes exposing the substrate to a metal precursor and then to an oxidation precursor. The exposing of the substrate is performed under pressure and temperature such that an inorganic material of a metal including the metal precursor is incorporated into the periodically repeating polymer structure, thereby forming a pattern of a periodically repeating optical structure configured to diffract visible light. The optical structure has a second refractive index greater than the first refractive index.

Description

[0001] Cross - Reference to Related Applications

[0002] This application claims the benefit of priority of U.S. Provisional Patent Application No. 62 / 613,651, filed on January 4, 2018, entitled "OPTICAL ELEMENTS BASED ON POLYMERIC STRUCTURES INCORPORATING INORGANIC MATERIALS", the entire content of which is incorporated herein by reference.

[0003] Incorporation by Reference

[0004] This application also incorporates by reference all of the following patent applications: U.S. Application No. 14 / 555,585, filed on November 27, 2014, which was published as U.S. Publication No. 2015 / 0205126 on July 23, 2015; U.S. Application No. 14 / 690,401, filed on April 18, 2015, which was published as U.S. Publication No. 2015 / 0302652 on October 22, 2015; U.S. Application No. 14 / 212,961, filed on March 14, 2014, now U.S. Patent No. 9,417,452, issued on August 16, 2016; U.S. Patent Application No. 14 / 331,218, filed on July 14, 2014, which was published as U.S. Publication No. 2015 / 0309263 on October 29, 2015. Technical Field

[0005] The present disclosure relates to display systems, and more particularly, to augmented reality systems. Background Art

[0006] Modern computing and display technologies have facilitated the development of systems for so - called "virtual reality" or "augmented reality" experiences, in which digitally reproduced images or portions thereof are presented to a user in a way that they appear real or can be perceived as real. Virtual reality or "VR" scenarios typically involve the presentation of digital or virtual image information without transparency to other actual real - world visual inputs; augmented reality or "AR" scenarios generally involve presenting digital or virtual image information as an enhancement to the visualization of the real world around the user. Mixed reality or "MR" scenarios are a type of AR scenario and typically involve virtual objects integrated into and responsive to the natural world. For example, an MR scenario may include AR image content that appears to be blocked by objects in the real world or otherwise perceived as interacting with objects in the real world.

[0007] Reference Figure 1, describes an augmented reality scenario 1. A user of AR technology sees a real-world park-like setting 20 characterized by people, trees, buildings in the background, and a concrete platform 30. The user also perceives that he "sees" "virtual content", such as a robotic figure 40 standing on the real-world platform 30, and a flying cartoon-like avatar character 50, which appears to be an anthropomorphic representation of a bumblebee. These elements 50, 40 are "virtual" because they do not exist in the real world. Since the human visual perception system is complex, it is challenging to develop AR technology that promotes a comfortable, natural-feeling, and rich presentation of virtual image elements with other virtual or real-world image elements.

[0008] The systems and methods disclosed herein address various challenges associated with AR and VR technologies. Summary of the Invention

[0009] In a first aspect, a method of manufacturing an optical element includes providing a substrate having a first refractive index and being transparent in the visible spectrum. The method further includes forming a periodically repeating polymer structure on the substrate. The method further includes exposing the substrate to a metal precursor and then to an oxidation precursor. The exposing of the substrate is performed under pressure and temperature such that an inorganic material of a metal including the metal precursor is incorporated into the periodically repeating polymer structure, thereby forming a pattern of a periodically repeating optical structure configured to diffract visible light. The optical structure has a second refractive index greater than the first refractive index.

[0010] In a second aspect, an optical element includes a substrate having a first refractive index and being transparent in the visible spectrum. The optical element further includes a pattern of a periodically repeating optical structure formed on the substrate and configured to diffract visible light. The optical structure has a second refractive index greater than the first refractive index and includes a polymer material in which an inorganic material is incorporated.

[0011] In a third aspect, an optical system includes an optical element. The optical element includes a substrate having a first refractive index and being transparent in the visible spectrum. The optical element further includes a pattern of a periodically repeating optical structure formed on the substrate and configured to diffract visible light. The optical structure has a second refractive index greater than the first refractive index and includes a polymer material in which an inorganic material is incorporated. The periodically repeating optical structure includes nanobeams arranged as a metasurface. The metasurface includes a plurality of repeating unit cells, where each unit cell includes a first group of nanobeams formed by one or more first nanobeams and a second group of nanobeams formed by one or more second nanobeams that are adjacently disposed to and spaced from the one or more first nanobeams by a subwavelength interval. The one or more first nanobeams and the plurality of second nanobeams extend in different orientation directions.

[0012] In a fourth aspect, an optical system includes a waveguide configured to propagate visible light. The optical system includes a substrate having a first refractive index and being transparent in the visible spectrum such that light can be guided therein by total internal reflection. The optical system further includes a pattern of periodically repeating optical structures formed on the substrate and configured to diffract visible light. The optical structures have a second refractive index greater than the first refractive index and include a polymeric material in which an inorganic material is incorporated. The periodically repeating optical structures are arranged to diffract light at a diffraction angle with respect to the direction of incident light and cause the diffracted light to propagate in the substrate under total internal reflection, or are arranged to diffract light that is guided in the substrate under total internal reflection at a diffraction angle with respect to the direction of the light guided in the substrate.

[0013] In a fifth aspect, a head-mounted display device is configured to project light onto a user's eye to display augmented reality image content. The head-mounted display device includes a frame configured to be supported on a user's head. The head-mounted display device further includes a display disposed on the frame, wherein at least a portion of the display includes one or more waveguides. The one or more waveguides are transparent and are arranged at a position in front of the user's eye when the user wears the head-mounted display device such that the transparent portion transmits light from a portion of the environment in front of the user to the user's eye to provide a view of the portion of the environment in front of the user. The head-mounted display device further includes one or more light sources and at least one diffraction grating configured to couple light from the light sources into the one or more waveguides or couple light out of the one or more waveguides. The at least one diffraction grating includes a substrate having a first refractive index and being transparent in the visible spectrum. The at least one diffraction grating additionally includes a pattern of periodically repeating optical structures formed on the substrate and configured to diffract visible light. The optical structures have a second refractive index greater than the first refractive index and include a polymeric material in which an inorganic material is incorporated.

[0014] In a sixth aspect, a method of manufacturing an optical element includes: providing a substrate that is transparent in the visible spectrum; forming a periodically repeating polymeric structure having a first refractive index on the substrate; and exposing the substrate to a metal precursor and then to an oxidizing precursor. The exposures are performed under pressure and temperature such that an inorganic material of a metal including the metal precursor is incorporated into the periodically repeating polymeric structure, thereby increasing the refractive index of the periodically repeating polymeric structure to form a pattern of periodically repeating optical structures configured to diffract visible light.

[0015] In a seventh aspect, a method of manufacturing an optical element includes: providing a substrate having a first refractive index and being transparent in the visible spectrum, wherein the substrate has a periodically repeating polymer structure formed thereon. The method further includes exposing the substrate to a metal precursor and then to an oxidation precursor. The exposures are performed under pressure and temperature such that an inorganic material of a metal including the metal precursor is incorporated into the periodically repeating polymer structure, thereby forming a pattern of a periodically repeating optical structure configured to diffract visible light, wherein the optical structure has a second refractive index greater than the first refractive index. Description of the Drawings

[0016] Figure 1 Shows a view of augmented reality (AR) of a user through an AR device.

[0017] Figure 2 Shows an example of a wearable display system.

[0018] Figure 3 Shows a conventional display system for simulating a three-dimensional image of a user.

[0019] Figure 4 Shows aspects of a method of simulating a three-dimensional image using multiple depth planes.

[0020] Figures 5A - 5C Shows the relationship between the radius of curvature and the radius of focus.

[0021] Figure 6 Shows an example of a waveguide stack for outputting image information to a user.

[0022] Figure 7 Shows an example of an output beam output from a waveguide.

[0023] Figure 8 Shows an example of a stacked waveguide assembly, wherein each depth plane includes an image formed using multiple different component colors.

[0024] Figure 9A Shows a cross-sectional side view of an example of a stacked waveguide group, each stacked waveguide including a coupled-in optical element.

[0025] Figure 9B Shows Figure 9A a perspective view of an example of multiple stacked waveguides.

[0026] Figure 9C Shows Figure 9A and 9B a top-down plan view of an example of multiple stacked waveguides.

[0027] Figure 10A cross-sectional view of an optical element is schematically shown, which includes a periodically repeated polymer-based optical structure incorporating an inorganic material therein.

[0028] Figure 11 A method of manufacturing an optical element is schematically shown, which includes a periodically repeated polymer-based optical structure incorporating an inorganic material therein.

[0029] Figures 12A - 12C It is a cross-sectional view of an intermediate structure at various stages of providing a periodically repeated base polymer structure using a lithography process.

[0030] Figures 13A - 13C It is a cross-sectional view of an intermediate structure at various stages of manufacturing a periodically repeated base polymer structure using a nanoimprint process.

[0031] Figures 14A - 14B It is a cross-sectional view of an intermediate structure at various stages of the manufacture of an optical element, which includes a periodically repeated polymer-based optical structure incorporating an inorganic material therein.

[0032] Figures 15A - 15B It is a cross-sectional view of an intermediate structure at various stages of the manufacture of an optical element, which includes a periodically repeated polymer-based optical structure incorporating an inorganic material therein.

[0033] Figures 16A - 16B It is a cross-sectional view of an intermediate structure at various stages of the manufacture of an optical element, which includes a periodically repeated polymer-based optical structure incorporating an inorganic material therein.

[0034] Figures 17A - 17H An optical element including a plurality of wave plate elements is shown, wherein each wave plate element includes a pattern of a periodically repeated polymer-based optical structure incorporating an inorganic material therein, and the figure shows the change in the polarization vector of the incident light, which respectively corresponds to the rotation of the wave plate element at angles θ of 0, π / 4, π / 2, 3π / 4, π, 5π / 4, 3π / 2, and 7π / 4 on the fast axis.

[0035] Figure 18A A cross-sectional side view of a diffraction grating is shown, which has a two-phase graded geometric phase optical element formed by a polymer-based optical structure incorporating an inorganic material therein.

[0036] Figure 18B Shows Figure 18A a top view of the diffraction grating of

[0037] Figure 19A top view of a diffraction grating is shown, the diffraction grating having a four-phase level geometric phase optical element formed from a polymer-based optical structure incorporating an inorganic material therein. Specific embodiments

[0038] Optical systems such as display systems often utilize optical elements to control the propagation of light. In some applications, due to the need for compact optical systems, optical elements having reduced dimensions (e.g., thin structures) can be useful. Such optical elements can include, for example, diffractive optical elements.

[0039] An example diffractive optical element is a diffraction grating for coupling light into an optical waveguide, for example. The optical waveguide can have, for example, a diffraction grating disposed thereon or therein, the diffraction grating being configured to couple light incident on the optical waveguide (e.g., at normal incidence) into the optical waveguide at an angle such that the diffracted light is guided within the optical waveguide by total internal reflection. A diffractive optical element such as a diffraction grating can be included within or on the optical waveguide to couple out light guided within the optical waveguide by total internal reflection. Diffractive optical elements can also be used to manipulate (e.g., redirect and / or modify) a light beam propagating within the optical waveguide by total internal reflection. Methods for manufacturing such diffractive optical elements as described herein can also be useful, which also provide increased confinement of light within the optical waveguide and / or increased diffraction efficiency.

[0040] Such diffractive optical elements can include a pattern of periodically repeating optical structures formed on a substrate and configured to diffract visible light, wherein the optical structures have a refractive index greater than that of the substrate. The diffractive optical element is formed from a polymer material incorporating an inorganic material therein. In some cases, the polymer material can be used as a photoresist that is retained as the final optical structure and can significantly reduce manufacturing complexity. Incorporating an inorganic material in the optical structure potentially allows for general tuning of optical properties such as refractive index and mechanical properties such as stiffness. Atomic layer deposition can be used to incorporate the inorganic material, which can enable precise control of the amount and depth of incorporation in the optical structure.

[0041] Another way to provide compact optical elements involves using thin films, such as diffraction gratings based on metasurfaces formed from thin-film-based nanostructures. Compared to geometric optical devices, metasurfaces or metamaterial surfaces offer the opportunity to implement nearly flat, aberration-free optical devices on a much smaller scale. Without being limited by theory, in some embodiments, the metasurface includes a dense arrangement of surface structures that act as resonant optical antennas. The resonant nature of the light-surface structure interaction provides the ability to manipulate the light wavefront. In some cases, the metasurface can allow the use of thin, relatively planar elements formed by a simple patterning process in place of bulky or difficult-to-fabricate optical components. However, the fabrication of thin-film-based optical elements can include patterning metal or high-refractive-index dielectric materials by lithography or nanoimprinting, both of which are expensive and / or difficult to achieve for structures with small sizes and / or complex shapes.

[0042] Advantageously, a polymer-based optical structure incorporating an inorganic material can be configured as a metasurface for forming various optical elements including diffraction gratings. The metasurface can take the form of a grating formed from a plurality of repeating unit cells. Each unit cell can include two or more sets of nanobeams elongated in the cross direction: one or more first nanobeams elongated in a first direction and a plurality of second nanobeams elongated in a second direction different from the first direction.

[0043] Some diffractive optical elements, such as diffractive optical elements including a metasurface formed from a polymer-based optical structure, can be used in wearable display systems to provide compact optical elements. An augmented reality system can display virtual content to a user or viewer while still allowing the user to see the world around them. The content can be displayed on a head-mounted display that can be mounted on the viewer's head. The head-mounted display can be, for example, part of glasses and project image information onto the user's eyes. Additionally, the display can also transmit light from the surrounding environment to the user's eyes to allow viewing of the surrounding environment.

[0044] Reference will now be made to the accompanying drawings, in which like reference numerals always denote like parts.

[0045] Example display system

[0046] Figure 2An example of a wearable display system 60 is shown. The display system 60 includes a display 70 and various mechanical and electronic modules and systems that support the functionality of the display 70. The display 70 may be coupled to a frame 80 that may be worn by a user or viewer 90 of the display system and is configured to position the display 70 in front of the eyes of the user 90. In some embodiments, the display 70 may be considered glasses. In some embodiments, a speaker 100 is coupled to the frame 80 and is configured to be positioned near the ear canal of the user 90 (in some embodiments, another speaker, not shown, may optionally be positioned near the other ear canal of the user to provide stereo / shapeable sound control). The display system may also include one or more microphones 110 or other devices to detect sound. In some embodiments, the microphone is configured to allow the user to provide input or commands to the system 60 (e.g., select voice menu commands, natural language questions, etc.) and / or may allow audio communication with other people (e.g., other users of a similar display system). The microphone may further be configured as a peripheral sensor to collect audio data (e.g., sounds from the user and / or the environment). In some embodiments, the display system may also include a peripheral sensor 120a that may be separate from the frame 80 and attached to the body of the user 90 (e.g., on the head, torso, limbs, etc. of the user 90). In some embodiments, the peripheral sensor 120a may be configured to acquire data representative of the physiological state of the user 90. For example, the sensor 120a may be an electrode.

[0047] Continuing reference Figure 2, the display 70 is operatively coupled to a local data processing module 140 via a communication link 130 (e.g., via a wired or wireless connection). The local data processing module 140 can be installed in various configurations, such as fixedly attached to the frame 80, fixedly attached to a helmet or hat worn by the user, embedded in headphones, or otherwise removably attached to the user 90 (e.g., in a backpack configuration, in a belt-coupled configuration). Similarly, the sensor 120a can be operatively coupled to the local processor and data module 140 via a communication link 120b (e.g., a wired wire or wireless connection). The local processing and data module 140 can include a hardware processor and a digital memory, such as a non-volatile memory (e.g., flash memory or hard disk drive), both of which can be used to assist in the processing, caching, and storage of data. The data includes data a) captured from sensors such as an image capture device (such as a camera), a microphone, an inertial measurement unit, an accelerometer, a compass, a GPS unit, a radio device, a gyroscope, and / or other sensors disclosed herein (which can be operatively coupled to the frame 80 or otherwise attached to the user 90); and / or data b) (including data related to virtual content) acquired and / or processed using the remote processing module 150 and / or the remote data repository 160, which may be used to be transmitted to the display 70 after such processing or retrieval. The local processing and data module 140 can be operatively coupled to the remote processing module 150 and the remote data repository 160 via communication links 170, 180 (e.g., via a wired or wireless communication link) so that these remote modules 150, 160 are operatively coupled to each other and can be available as resources for the local processing and data module 140. In some embodiments, the local processing and data module 140 can include one or more of an image capture device, a microphone, an inertial measurement unit, an accelerometer, a compass, a GPS unit, a radio device, and / or a gyroscope. In some other embodiments, one or more of these sensors can be attached to the frame 80 or can be an independent structure that communicates with the local processing and data module 140 via a wired or wireless communication path.

[0048] Continue to refer to Figure 2, in some embodiments, the remote processing module 150 may include one or more processors configured to analyze and process data and / or image information. In some embodiments, the remote data repository 160 may include a digital data storage facility that may be available via the Internet or other network configurations in a "cloud" resource configuration. In some embodiments, the remote data repository 160 may include one or more remote servers that provide information to the local processing and data module 140 and / or the remote processing module 150, such as information for generating augmented reality content. In some embodiments, all data is stored and all computations are performed in the local processing and data module, allowing for the full autonomous use of the remote module.

[0049] Now refer to Figure 3 , by providing slightly different image presentations to each eye of a viewer, an image can be perceived as "three-dimensional" or "3-D". Figure 3 A conventional display system for simulating three-dimensional images for a user is shown. Two different images 190, 200 are output to the user, one for each eye 210, 220. The images 190, 200 are separated from the eyes 210, 220 by a distance 230 along a light or z-axis parallel to the viewer's line of sight. The images 190, 200 are planar, and the eyes 210, 220 can focus on the images by presenting a single accommodate state. Such a system relies on the human visual system to combine the images 190, 200 in order to provide a perception of depth and / or scale for the combined image.

[0050] However, it is understood that the human visual system is more complex and it is more challenging to provide true depth perception. For example, many viewers of traditional "3-D" display systems find such systems uncomfortable or do not perceive a sense of depth at all. Without being limited by theory, a viewer of an object may perceive the object as "three-dimensional" due to a combination of vergence and accommodation. The vergence movement of the two eyes relative to each other (i.e., the rotation of the eyes such that the pupils move towards or away from each other to converge the lines of sight of the eyes to fixate on an object) is closely related to the focusing (or "accommodation") of the lenses and pupils of the eyes. Under normal circumstances, under what is known as the "accommodation-vergence reflex" and the relationship of pupillary dilation or constriction, changing the focal length of the lens of the eye or accommodating the eye to change the focus from one object to another object at a different distance will automatically result in a matching change in vergence to the same distance. Similarly, under normal conditions, a change in vergence will trigger a matching change in accommodation of the lens shape and pupil size. As described herein, many stereoscopic or "3-D" display systems use slightly different presentations (and thus slightly different images) to display a scene to each eye so that the human visual system perceives three-dimensional perspective. However, such systems are uncomfortable for many viewers because, among other things, they simply provide different presentations of the scene, but the eyes view all the image information in a single accommodation state and violate the "accommodation-vergence reflex". A display system that provides a better match between accommodation and vergence can create a more realistic and comfortable simulation of a three-dimensional image.

[0051] Figure 4 Aspects of a method for simulating a three-dimensional image using multiple depth planes are shown. Referring to Figure 4 , objects at different distances from eyes 210, 220 along the z-axis are accommodated by eyes 210, 220 such that those objects are in focus. The eyes (210 and 220) assume a particular accommodation state in order to focus on objects located at different distances along the z-axis. Thus, a particular accommodation state can be considered to be associated with a particular one of depth planes 240, having an associated focal length such that when the eyes are in the accommodation state for that depth plane, the objects or portions of objects in the particular depth plane are in focus. In some embodiments, a three-dimensional image can be simulated by providing a different presentation of the image for each of eyes 210, 220 and also by providing a different presentation of the image corresponding to each of the depth planes. Although shown as separate for clarity of illustration, it should be understood that the fields of view of eyes 210, 220 may overlap, for example, as the distance along the z-axis increases. Additionally, although shown as flat for ease of illustration, it should be understood that the profile of the depth plane may be curved in physical space so that all features in the depth plane are in focus when the eyes are in a particular accommodation state.

[0052] The distance between an object and an eye 210 or 220 can also change the amount of divergence of the light from the object that the eye sees. Figures 5A - 5C The relationship between distance and light divergence is shown. The distances between the object and the eye 210 are represented by R1, R2, and R3 in decreasing order of distance. As Figures 5A - 5C shown, the light becomes more divergent as the distance to the object decreases. As the distance increases, the light becomes more collimated. In other words, the light field that may be generated by a point (an object or a part of an object) has a spherical wavefront curvature that is a function of how far that point is from the user's eye. The curvature increases as the distance between the object and the eye 210 decreases. Thus, at different depth planes, the degree of divergence of the light is also different, where the degree of divergence increases as the distance between the depth plane and the viewer's eye 210 decreases. Although, for clarity of illustration, only a single eye 210 is shown in Figures 5A - 5C and other figures here, it should be understood that the discussion regarding the eye 210 applies to both eyes 210 and 220 of the viewer.

[0053] Without being limited by theory, it is believed that the human eye can generally interpret a limited number of depth planes to provide depth perception. Thus, by providing the eyes with different renditions of an image corresponding to each of these limited number of depth planes, a highly believable simulation of perceived depth can be achieved. The different renditions can be separately focused by the viewer's eyes, thereby helping to provide depth cues to the user based on the eye accommodation required to focus on different image features of a scene located at different depth planes and / or based on observing different image features of different depth planes that are out of focus.

[0054] Figure 6 An example of a waveguide stack for outputting image information to a user is shown. The display system 250 includes a stack of waveguides or a stacked waveguide assembly 260 that can be used to provide three-dimensional perception to the eye / brain using multiple waveguides 270, 280, 290, 300, 310. In some embodiments, the display system 250 is Figure 2 system 60, Figure 6 which more schematically shows some parts of that system 60 in more detail. For example, the waveguide assembly 260 can be part of Figure 2 display 70. It should be understood that in some embodiments, the display system 250 can be considered a light field display.

[0055] Continuing to refer to Figure 6, the waveguide assembly 260 may further include a plurality of features 320, 330, 340, 350 between waveguides. In some embodiments, the features 320, 330, 340, 350 may be one or more lenses. The waveguides 270, 280, 290, 300, 310 and / or the plurality of lenses 320, 330, 340, 350 may be configured to send image information to the eye with various levels of wavefront curvature or light divergence. Each waveguide stage may be associated with a particular depth plane and may be configured to output image information corresponding to that depth plane. The image injection devices 360, 370, 380, 390, 400 may be used as light sources for the waveguides and may be used to inject image information into the waveguides 270, 280, 290, 300, 310, and each waveguide may be configured to distribute incident light across each respective waveguide for output to the eye 210 as described herein. Light exits from the output surfaces 410, 420, 430, 440, 450 of the image injection devices 360, 370, 380, 390, 400 and is injected into the corresponding input surfaces 460, 470, 480, 490, 500 of the waveguides 270, 280, 290, 300, 310. In some embodiments, each of the input surfaces 460, 470, 480, 490, 500 may be an edge of the corresponding waveguide or may be a part of the major surface of the corresponding waveguide (i.e., the one of the waveguide surfaces that directly faces the world 510 or the viewer's eye 210). In some embodiments, a single light beam (e.g., a collimated beam) may be injected into each waveguide to output an entire field of cloned collimated beams that are directed toward the eye 210 at a particular angle (and amount of divergence) corresponding to the depth plane associated with the particular waveguide. In some embodiments, a single one of the image injection devices 360, 370, 380, 390, 400 may be associated with a plurality (e.g., three) of the waveguides 270, 280, 290, 300, 310 and inject light into the plurality of waveguides.

[0056] In some embodiments, the image injection devices 360, 370, 380, 390, 400 are discrete displays, and each discrete display separately generates image information for injection into the corresponding waveguides 270, 280, 290, 300, 310. In some other embodiments, the image injection devices 360, 370, 380, 390, 400 are output ports of a single multiplexed display that may transfer image information to each of the image injection devices 360, 370, 380, 390, 400 via, for example, one or more light ducts (such as fiber optic cables). It should be understood that the image information provided by the image injection devices 360, 370, 380, 390, 400 may include light of different wavelengths or colors (e.g., different component colors as described herein).

[0057] In some embodiments, the light injected into waveguides 270, 280, 290, 300, 310 is provided by a light projector system 520 that includes a light module 530 containing a light emitter (e.g., a light-emitting diode (LED)). The light from the light module 530 can be directed to and modified by a light modulator 540 (e.g., a spatial light modulator) via a beam splitter 550. The light modulator 540 can be configured to change the perceived intensity of the light injected into waveguides 270, 280, 290, 300, 310. Examples of spatial light modulators include liquid crystal displays (LCDs) that include liquid crystal on silicon (LCOS) displays.

[0058] In some embodiments, the display system 250 can be a scanning fiber optic display that includes one or more scanning optical fibers configured to project light into one or more waveguides 270, 280, 290, 300, 310 in various patterns (e.g., raster scan, helical scan, Lissajous pattern, etc.) and ultimately into the viewer's eye 210. In some embodiments, the illustrated image injection devices 360, 370, 380, 390, 400 can schematically represent a single scanning optical fiber or a bundle of scanning optical fibers configured to inject light into one or more waveguides 270, 280, 290, 300, 310. In some other embodiments, the exemplary image injection devices 360, 370, 380, 390, 400 can schematically represent multiple scanning optical fibers or multiple bundles of scanning optical fibers, each scanning optical fiber being configured to inject light into an associated one of the waveguides 270, 280, 290, 300, 310. It will be understood that the one or more optical fibers can be configured to transmit light from the light module 530 to the one or more waveguides 270, 280, 290, 300, 310. It should be understood that one or more intermediate optical structures can be provided between the scanning optical fiber(s) and the one or more waveguides 270, 280, 290, 300, 310 to, for example, redirect the light exiting the scanning optical fiber into the one or more waveguides 270, 280, 290, 300, 310.

[0059] The controller 560 controls the operation of one or more of the stacked waveguide assemblies 260, including the operation of the image injection devices 360, 370, 380, 390, 400, the light source 530, and the light modulator 540. In some embodiments, the controller 560 is part of the local data processing module 140. The controller 210 includes a program (e.g., instructions in a non-transitory medium) that regulates the timing and provision of image information to the waveguides 270, 280, 290, 300, 310 according to any of the various schemes disclosed herein, for example. In some embodiments, the controller can be a single integrated device or a distributed system connected via wired or wireless communication channels. In some embodiments, the controller 560 can be part of the processing module 140 or 150( Figure 2 ).

[0060] Continuing to refer Figure 6 , the waveguides 270, 280, 290, 300, 310 can be configured to propagate light by total internal reflection (TIR) within each respective waveguide. The waveguides 270, 280, 290, 300, 310 can each be planar or have another shape (e.g., curved), having a major top and bottom surface and an edge extending between these major top and bottom surfaces. In an example configuration, each of the waveguides 270, 280, 290, 300, 310 can include outcoupling optical elements 570, 580, 590, 600, 610, which are configured to extract light from the waveguide by redirecting the light propagating within each respective waveguide out of the waveguide to output image information to the eye 210. The extracted light can also be referred to as outcoupled light, and the outcoupling optical elements can also be referred to as light extraction optical elements. The extracted light beam can be output from the waveguide at the location where the light propagating in the waveguide is incident on the light extraction optical element. The outcoupling optical elements 570, 580, 590, 600, 610 can be, for example, gratings, which include diffractive optical features, as further discussed herein. Although shown for ease of description and clarity of the drawings as being disposed at the bottom major surface of the waveguides 270, 280, 290, 300, 310, in some embodiments, the outcoupling optical elements 570, 580, 590, 600, 610 can be disposed at the top and / or bottom major surfaces, and / or can be disposed directly within the volume of the waveguides 270, 280, 290, 300, 310, as further discussed herein. In some embodiments, the outcoupling optical elements 570, 580, 590, 600, 610 can be formed in a material layer attached to a transparent substrate to form the waveguides 270, 280, 290, 300, 310. In some other embodiments, the waveguides 270, 280, 290, 300, 310 can be a single piece of material, and the outcoupling optical elements 570, 580, 590, 600, 610 can be formed on and / or within the surface of the piece of material.

[0061] Continue to refer to Figure 6 , as discussed herein, each of waveguides 270, 280, 290, 300, 310 is configured to output light to form an image corresponding to a particular depth plane. For example, the waveguide 270 closest to the eye may be configured to transmit collimated light (which is injected into the waveguide 270) to the eye 210. The collimated light may represent an optically infinite focal plane. The next upper waveguide 280 may be configured to emit collimated light that passes through a first lens 350 (e.g., a negative lens) before reaching the eye 210; such a first lens 350 may be configured to produce a slightly convex wavefront curvature so that the eye / brain interprets the light from the next upper waveguide 280 as coming from a first focal plane that is more inward from the optically infinite towards the eye 210. Similarly, the third upper waveguide 290 passes its output light through the first lens 350 and the second lens 340 before reaching the eye 210; the combined optical power of the first lens 350 and the second lens 340 may be configured to produce another increment of wavefront curvature such that the eye / brain interprets the light from the third waveguide 290 as coming from a second focal plane that is more inward from the optically infinite towards the person than the light from the next upper waveguide 280.

[0062] The other waveguide layers 300, 310 and lenses 330, 320 are configured similarly, where the highest waveguide 310 in the stack sends its output through all of the lenses between it and the eye for the total optical power of the focal plane closest to the person. To compensate for the stack of lenses 320, 330, 340, 350 when observing / interpreting light from the world 510 on the other side of the stacked waveguide assembly 260, a compensation lens layer 620 may be provided on top of the stack to compensate for the total optical power of the underlying lens stack 320, 330, 340, 350. Such a configuration provides as many perceived focal planes as there are available waveguide / lens pairs. Both the outcoupling optical elements of the waveguides and the focusing aspects of the lenses may be static (i.e., not dynamic or electrically activated). In some alternative embodiments, electrically active features are used, where one or both of them may be dynamic.

[0063] In some embodiments, two or more of the waveguides 270, 280, 290, 300, 310 may have the same associated depth plane. For example, multiple waveguides 270, 280, 290, 300, 310 may be configured to output a set of images to the same depth plane, or multiple subsets of the waveguides 270, 280, 290, 300, 310 may be configured to output a set of images to the same multiple depth planes, where each depth plane has a set. This may provide the advantage of forming a tiled image to provide an extended field of view at those depth planes.

[0064] Continue to refer to Figure 6, the output optical elements 570, 580, 590, 600, 610 can be configured to redirect light out of their respective waveguides and output the light with an appropriate amount of divergence or collimation for a particular depth plane associated with the waveguide. As a result, waveguides having different associated depth planes can have differently configured output optical elements 570, 580, 590, 600, 610, which output light with different amounts of divergence depending on the associated depth plane. In some embodiments, the light extraction optical elements 570, 580, 590, 600, 610 can be volume features or surface features that can be configured to output light at a particular angle. For example, the light extraction optical elements 570, 580, 590, 600, 610 can be volume holograms, surface holograms, and / or diffraction gratings. In some embodiments, the features 320, 330, 340, 350 can not be lenses; rather, they can simply be spacers (e.g., claddings and / or structures for forming an air gap).

[0065] In some embodiments, the output optical elements 570, 580, 590, 600, 610 are diffraction features that form a diffraction pattern, or "diffractive optical elements" (also referred to herein as "DOEs"). Preferably, only a portion of the light of the light beam is deflected out towards the eye 210 at each intersection with the DOE, while the remaining light continues to travel through the waveguide by TIR. As a result, the light carrying the image information is split into multiple related outgoing light beams that exit the waveguide at multiple locations, and the result is a relatively uniform outgoing emission pattern towards the eye 210 for such a particular collimated light beam reflected within the waveguide.

[0066] In some embodiments, one or more DOEs can be switched between an "on" state in which they actively diffract and an "off" state in which they do not significantly diffract. For example, a switchable DOE can include a polymer dispersed liquid crystal layer, where microdroplets contain a diffraction pattern in a host medium, and the refractive index of the microdroplets can be switched to be substantially matched to the refractive index of the host material (in which case the pattern does not significantly diffract the incident light), or the microdroplets can be switched to a refractive index that does not match the refractive index of the host medium (in which case the pattern actively diffracts the incident light).

[0067] In some embodiments, a camera assembly 630 (e.g., a digital camera, including visible light and infrared light cameras) can be provided to capture an image of the eye 210 and / or the tissue surrounding the eye 210 to, for example, detect user input and / or monitor the physiological state of the user. As used herein, a camera can be any image capture device. In some embodiments, the camera assembly 630 can include an image capture device and a light source to project light (e.g., infrared light) onto the eye, and then the light can be reflected by the eye and detected by the image capture device. In some embodiments, the camera assembly 630 can be attached to the frame 80(Figure 2 ) and can be in electrical communication with processing module 140 and / or 150, which can process image information from camera assembly 630. In some embodiments, one camera assembly 630 can be used for each eye to monitor each eye separately.

[0068] Now referring to Figure 7 , an example of an output beam exiting a waveguide is shown. One waveguide is shown, but it should be understood that other waveguides in waveguide assembly 260 ( Figure 6 ) can operate similarly, where waveguide assembly 260 includes multiple waveguides. Light 640 is injected into waveguide 270 at input surface 460 of waveguide 270 and propagates within waveguide 270 by TIR. At the point where light 640 impinges on DOE 570, a portion of the light exits the waveguide as output beam 650. Output beam 650 is shown as being substantially parallel, but as discussed herein, they can also be redirected to propagate at an angle to eye 210 depending on the depth plane associated with waveguide 270 (e.g., forming a diverging output beam). It should be understood that substantially parallel output beams can represent a waveguide having an outcoupling optical element that couples light out to form an image that appears to be disposed on a depth plane at a large distance from eye 210 (e.g., optical infinity). Other waveguides or other sets of outcoupling optical elements can output a more diverging output beam pattern, which would require eye 210 to accommodate to a closer distance to focus on the retina and would be interpreted by the brain as light from a distance closer to eye 210 than optical infinity.

[0069] In some embodiments, a full-color image can be formed at each depth plane by overlaying an image of each of the component colors (e.g., three or more component colors). Figure 8An example of a stacked waveguide assembly is shown, where each depth plane includes an image formed using multiple different component colors. The illustrated embodiment shows depth planes 240a - 240f, although more or fewer depths may also be considered. Each depth plane may have three or more component color images associated therewith, including: a first image of a first color, G; a second image of a second color, R; and a third image of a third color, B. In the figure, different depth planes are represented by different numbers of diopters (dpt) after the letters G, R, and B. By way of example only, the number after each of these letters indicates the diopter (1 / m) or the reciprocal of the distance of the depth plane from the viewer, and each box in the figure represents a separate component color image. In some embodiments, the exact setting of the depth planes of different component colors may vary, taking into account the differences in the focusing of the eye on light of different wavelengths. For example, the different component color images for a given depth plane may be set on depth planes corresponding to different distances from the user. Such a setting may increase visual acuity and user comfort and / or may reduce chromatic aberration.

[0070] In some embodiments, light of each component color may be output by a single dedicated waveguide, and thus, each depth plane may have multiple waveguides associated therewith. In such an embodiment, each box in the figure including the letters G, R, or B may be understood to represent a separate waveguide, and three waveguides may be provided for each depth plane, where three component color images are provided for each depth plane. Although the waveguides associated with each depth plane are shown adjacent to each other in this figure for ease of description, it will be understood that in a physical device, the waveguides may all be in a stacked arrangement, one waveguide per level. In some other embodiments, multiple component colors may be output by the same waveguide, such that, for example, each depth plane may provide only a single waveguide.

[0071] Continuing to refer to Figure 8 , in some embodiments, G is green, R is red, and B is blue. In some other embodiments, in addition to or instead of one or more of red, green, or blue, other colors associated with light of other wavelengths may be used, including magenta and cyan.

[0072] It will be understood that in the present disclosure, a reference to light of a given color will be understood to encompass light of one or more wavelengths within the wavelength range of light that a viewer perceives as having that given color. For example, red light may include light of one or more wavelengths in the range of approximately 620 - 780 nm, green light may include light of one or more wavelengths in the range of approximately 492 - 577 nm, and blue light may include light of one or more wavelengths in the range of approximately 435 - 493 nm.

[0073] In some embodiments, light source 530 ( Figure 6) can be configured to emit light at one or more wavelengths outside the viewer's visual perception range, such as infrared and / or ultraviolet wavelengths. Additionally, the input, output, and other light redirecting structures of the waveguide of the display 250 can be configured to direct and emit such light out of the display towards the user's eye 210, e.g., for imaging and / or user stimulation applications.

[0074] Now referring to Figure 9A , in some embodiments, light incident on the waveguide may need to be redirected to couple the light into the waveguide. Input optics can be used to redirect and couple the light into its corresponding waveguide. Figure 9A A cross-sectional side view showing an example of a plurality or a stack 660 of stacked waveguides is shown, each stacked waveguide including input optics. Each waveguide can be configured to output light at one or more different wavelengths, or one or more different wavelength ranges. It should be understood that the stack 660 can correspond to the stack 260 ( Figure 6 ), and the example waveguides of the stack 660 can correspond to a portion of the plurality of waveguides 270, 280, 290, 300, 310.

[0075] The exemplary stacked waveguide group 660 includes waveguides 670, 680, and 690. Each waveguide includes an associated coupling-in optical element (which may also be referred to as a light input region on the waveguide), such as a coupling-in optical element 700 disposed on a major surface (e.g., an upper major surface) of the waveguide 670, a coupling-in optical element 710 disposed on a major surface (e.g., an upper major surface) of the waveguide 680, and a coupling-in optical element 720 disposed on a major surface (e.g., an upper major surface) of the waveguide 690. In some embodiments, one or more of the coupling-in optical elements 700, 710, 720 may be disposed on the bottom major surface of the respective waveguide 670, 680, 690 (particularly, in the case where one or more coupling-in optical elements are reflective, deflecting optical elements). As an example, the coupling-in optical elements 700, 710, 720 may be disposed on the upper major surface (or the top of the next lower waveguide) of their respective waveguides 670, 680, 690, particularly in the case where the coupling-in optical elements are transmissive, deflecting optical elements. In some embodiments, the coupling-in optical elements 700, 710, 720 may be disposed in the body of the respective waveguides 670, 680, 690. In some embodiments, as discussed herein, the coupling-in optical elements 700, 710, 720 are wavelength selective such that they selectively redirect light of one or more wavelengths while transmitting light of other wavelengths. Although shown on a side or corner of their respective waveguides 670, 680, 690, it should be understood that in some embodiments, the coupling-in optical elements 700, 710, 720 may be disposed in other areas of their respective waveguides 670, 680, 690.

[0076] As illustrated, the coupling-in optical elements 700, 710, 720 can be laterally offset from each other. In some embodiments, each coupling-in optical element can be offset so that it receives light without the light passing through another coupling-in optical element. For example, each coupling-in optical element 700, 710, 720 can be configured to be offset from, for example, Figure 6 The different image injection devices 360 , 370 , 380 , 390 , and 400 shown receive light and may be separated (eg, laterally spaced) from the other incoupling optical elements 700 , 710 , 720 so that they do not substantially receive light from the other incoupling optical elements 700 , 710 , 720 .

[0077] Each waveguide also includes an associated light distribution element, such as a light distribution element 730 disposed on a main surface (e.g., a top main surface) of waveguide 670, a light distribution element 740 disposed on a main surface (e.g., a top main surface) of waveguide 680, and a light distribution element 750 disposed on a main surface (e.g., a top main surface) of waveguide 690. In some other embodiments, the light distribution elements 730, 740, 750 may be respectively disposed on the bottom main surfaces of the associated waveguides 670, 680, 690. In some other embodiments, the light distribution elements 730, 740, 750 may be respectively disposed on both the top main surface and the bottom main surface of the associated waveguides 670, 680, 690; or the light distribution elements 730, 740, 750 may be respectively disposed on a different one of the top main surface and the bottom main surface in different associated waveguides 670, 680, 690.

[0078] Waveguides 670, 680, 690 may be spaced apart and separated by, for example, a gas, a liquid, and / or a solid material layer. For example, as illustrated, layer 760a may separate waveguides 670 and 680; and layer 760b may separate waveguides 680 and 690. In some embodiments, layers 760a and 760b are formed of a low refractive index material (i.e., a material having a refractive index lower than that of the material forming the immediately adjacent one of waveguides 670, 680, 690). Preferably, the refractive index of the material forming layers 760a, 760b is 0.05 or more less, or 0.10 less, than the refractive index of the material forming waveguides 670, 680, 690. Advantageously, the lower refractive index layers 760a, 760b can be used as claddings to facilitate total internal reflection (TIR) of light through waveguides 670, 680, 690 (e.g., TIR between the top and bottom main surfaces of each waveguide). In some embodiments, layers 760a, 760b are formed of air. Although not shown, it will be understood that the top and bottom of the exemplary waveguide group 660 may include adjacent claddings.

[0079] Preferably, for ease of manufacturing and other considerations, the materials forming waveguides 670, 680, 690 are similar or the same, and the materials forming layers 760a, 760b are similar or the same. In some embodiments, the materials forming waveguides 670, 680, 690 may be different between one or more waveguides, and / or the materials forming layers 760a, 760b may be different, while still maintaining the various refractive index relationships described above.

[0080] Continuing to refer Figure 9A , light rays 770, 780, 790 are incident on waveguide group 660. It should be understood that light rays 770, 780, 790 may pass through one or more image injection devices 360, 370, 380, 390, 400 ( Figure 6)Injected into waveguides 670, 680, 690.

[0081] In some embodiments, the light rays 770, 780, 790 have different characteristics, e.g., different wavelengths or different wavelength ranges, which may correspond to different colors. Each of the coupling optical elements 700, 710, 720 deflects the incident light so that the light propagates through the corresponding one of the waveguides 670, 680, 690 by TIR. In some embodiments, each of the coupling optical elements 700, 122, 720 selectively deflects light of one or more specific wavelengths while transmitting other wavelengths to the underlying waveguide and the associated coupling optical element.

[0082] For example, the coupling optical element 700 may be configured to deflect the light ray 770 having a first wavelength or wavelength range while transmitting the light rays 780 and 790 having different second and third wavelengths or wavelength ranges, respectively. Then, the transmitted light ray 780 is incident on the coupling optical element 710 and is deflected by it, and the coupling optical element 710 is configured to selectively deflect the light of the second wavelength or wavelength range. The light ray 790 is deflected by the coupling optical element 720, and the coupling optical element 720 is configured to selectively deflect the light of the third wavelength or wavelength range.

[0083] Continuing to refer to Figure 9A , the deflected light rays 770, 780, 790 are deflected so that they propagate through the corresponding waveguides 670, 680, 690; that is, the coupling optical elements 700, 710, 720 of each waveguide deflect the light into the corresponding waveguide 670, 680, 690 to couple the light into the corresponding waveguide. The light rays 770, 780, 790 are deflected at an angle such that the light propagates through the corresponding waveguides 670, 680, 690 by TIR. The light rays 770, 780, 790 propagate through the corresponding waveguides 670, 680, 690 by TIR until they are incident on the corresponding light distribution elements 730, 740, 750 of the waveguides.

[0084] Now referring to Figure 9B , a perspective view of an example of a plurality of stacked waveguides of Figure 9A is shown. As described above, the coupled light rays 770, 780, 790 are respectively deflected by the coupling optical elements 700, 710, 720 and then propagate through the waveguides 670, 680, 690 by TIR, respectively. Then, the light rays 770, 780, 790 are respectively incident on the light distribution elements 730, 740, 750. The light distribution elements 730, 740, 750 deflect the light rays 770, 780, 790 so that they propagate toward the coupling-out optical elements 800, 810, 820, respectively.

[0085] In some embodiments, the light distribution elements 730, 740, 750 are orthogonal pupil expanders (OPEs). In some embodiments, the OPE deflects or distributes light to the output optical elements 800, 810, 820, and in some embodiments, also increases the beam or spot size of the light as it propagates to the output optical elements. In some embodiments, the light distribution elements 730, 740, 750 may be omitted, and the input optical elements 700, 710, 720 may be configured to deflect light directly to the output optical elements 800, 810, 820. For example, referring to Figure 9A , the light distribution elements 730, 740, 750 may be replaced by the output optical elements 800, 810, 820, respectively. In some embodiments, the output optical elements 800, 810, 820 are exit pupils (EPs) or exit pupil expanders (EPEs) that direct light to the viewer's eye 210 ( Figure 7 ). It should be understood that the OPE can be configured to increase the size of the eye box along at least one axis, and the EPE can increase the eye box along an axis orthogonal to the axis of the OPE, for example. For example, each OPE can be configured to redirect a portion of the light that strikes the OPE to the EPE of the same waveguide, while allowing the remaining portion of the light to continue propagating downward along the waveguide. After striking the OPE again, another portion of the remaining light is redirected to the EPE, and the remaining portion of that portion continues to propagate further downward along the waveguide, and so on. Similarly, after striking the EPE, a portion of the incident light is directed out of the waveguide towards the user, and the remaining portion of the light continues to propagate through the waveguide until it strikes the EP again, at which point another portion of the incident light is directed out of the waveguide, and so on. Thus, each time a portion of the light is redirected by the OPE or EPE, a single beam of coupled-in light can be "copied", thereby forming a field of cloned beams, as shown in Figure 6 . In some embodiments, the OPE and / or EPE can be configured to modify the size of the beam.

[0086] Thus, referring to Figure 9A and 9B, in some embodiments, the waveguide group 660 includes waveguides 670, 680, 690; input optical elements 700, 710, 720; light distribution elements (e.g., OPE) 730, 740, 750; and output optical elements (e.g., EP) 800, 810, 820 for each component color. The waveguides 670, 680, 690 can be stacked with an air gap / cladding between each waveguide. The input optical elements 700, 710, 720 redirect or deflect the incident light (where different input optical elements receive light of different wavelengths) into their waveguides. Then, the light propagates at an angle that will result in TIR within the respective waveguides 670, 680, 690. In the example shown, the light ray 770 (e.g., blue light) is deflected by the first input optical element 700 and then continues to reflect along the waveguide, interacting with the light distribution element (e.g., OPE) 730 and then the output coupling optical element (e.g., EP) 800 in the manner previously described. The light rays 780 and 790 (e.g., green light and red light, respectively) will pass through the waveguide 670. The light ray 780 is incident on the input optical element 710 and is deflected by it. Then, the light ray 780 is reflected along the waveguide 680 via TIR, proceeds to its light distribution element (e.g., OPE) 740, and then proceeds to the output optical element (e.g., EP) 810. Finally, the light ray 790 (e.g., red light) passes through the waveguide 690 to be incident on the light input optical element 720 of the waveguide 690. The light input optical element 720 deflects the light ray 790 so that the light ray propagates to the light distribution element (e.g., OPE) 750 via TIR and then to the output optical element (e.g., EP) 820 via TIR. Then, the output optical element 820 finally couples out the light ray 790 to the viewer, and the viewer also receives the output light from the other waveguides 670, 680.

[0087] Figure 9C shows Figure 9A and 9B A top-down plan view of an example of a plurality of stacked waveguides. As shown in the example, the waveguides 670, 680, 690 together with the associated light distribution elements 730, 740, 750 and the associated output optical elements 800, 810, 820 of each waveguide can be vertically aligned. However, as discussed herein, the input optical elements 700, 710, 720 are not vertically aligned; rather, the input optical elements are preferably non-overlapping (e.g., laterally spaced apart as seen in the top-down view). As further discussed herein, this non-overlapping spatial arrangement facilitates the injection of light from different sources one-to-one into different waveguides, thereby allowing a specific light source to be uniquely coupled to a specific waveguide. In some embodiments, an arrangement including non-overlapping spatially separated input optical elements can be referred to as a shifted pupil system, and the input optical elements within these arrangements can correspond to sub-pupils.

[0088] Optical element formed from a polymer - based optical structure incorporating an inorganic material

[0089] A display system can employ various optical elements to control the propagation of light. However, in some cases, such as a display system including a head-mounted display device (e.g., the display system 80 referred to above with reference to Figure 2 ), conventional optical elements may not be ideal or suitable due to their relatively heavy weight, large size, manufacturing challenges, and / or insufficient optical characteristics (such as diffraction angle and diffraction efficiency).

[0090] For example, as referred to above with reference to Figures 9A - 9C , a display system can include optical elements (e.g., an input-coupling optical element, a light distribution element, and an output-coupling optical element), which can include diffraction gratings. Additionally, as further described above with reference to Figures 9A - 9C , light coupled into a corresponding waveguide can propagate within the waveguide by total internal reflection (TIR). To achieve TIR, it may be desirable for the diffraction grating to have a relatively high diffraction angle with respect to the surface normal. Additionally, a high diffraction efficiency may be desired to increase the light intensity and image brightness. However, providing a diffraction grating that can achieve a high diffraction angle and high diffraction efficiency for visible light presents challenges. To meet these and other requirements, examples of optical elements disclosed herein, such as diffraction gratings, can utilize optical elements formed from a periodically repeating polymer-based optical structure in which an inorganic material is incorporated.

[0091] Figure 10 A cross-sectional view of an optical element (e.g., diffraction grating 1000) according to various embodiments is shown, the optical element including a periodically repeating polymer-based optical structure in which an inorganic material is incorporated. Diffraction grating 1000 includes a substrate 1004 having a first refractive index (n 1 ) and being transparent in the visible spectrum. Diffraction grating 1000 further includes a pattern of periodically repeating optical structures 1008 formed on substrate 1004 and configured to diffract visible light. Optical structures 1008 have a second refractive index (n 2 ) greater than the first refractive index and include a polymer material in which an inorganic material is incorporated.

[0092] According to an embodiment, the substrate 1004 is transparent in the visible spectrum. As described herein and throughout the specification, a "transmissive" or "transparent" structure, such as a transmissive substrate, can allow at least some, such as at least 20, 30, 50, 70, 90%, or 95% of incident light to pass through but can transmit less than 99% or 100%. The transmission percentage can be within any range defined by any of these values, or can be outside these ranges. Therefore, in some embodiments, the transparent substrate can be a glass, sapphire, or polymer substrate. A "reflective" structure, such as a reflective substrate, can reflect at least some, such as at least 20, 30, 50, 70, 90%, or 95% or more of incident light but reflect less than 99% or 100%. The reflection percentage can be within any range defined by any of these values, or can be outside these ranges.

[0093] According to an embodiment, the substrate 1004 has a first refractive index (n 1 ), the first refractive index (n 1 ) is greater than the refractive index of air but less than the second refractive index n of the optical structure 1008 2 .n 1 The substrate 1004 may have a value of, for example, about 1.5, 1.6, 1.7, 1.8, 1.9, or any value within or outside any range bounded by these values. Examples of materials for forming the substrate 1004 include silica glass (e.g., doped silica glass), silicon oxynitride, transition metal oxides (e.g., hafnium oxide, tantalum oxide, zirconium oxide, niobium oxide, lithium niobate, aluminum oxide (e.g., sapphire)), plastics, polymers, or other optically transmissive materials having a suitable refractive index, such as described herein.

[0094] The pattern of periodically repeating optical structures 1008 formed on substrate 1004 is configured to diffract visible light due to materials, dimensions, and geometric configurations such as described herein.

[0095] Still reference Figure 10 According to various embodiments, the optical structure 1008 includes a base polymer material in which an inorganic material is combined. The base polymer material may include a suitable polymer for combining the inorganic material and serving as a material that can be patterned photolithographically, such as a photosensitive material that can be patterned photolithographically (e.g., a photoresist or another material that can be easily patterned). For example, the base polymer material may include polyethylene (PE) (–(CH 2 -CH 2 ) n –)), polypropylene (PP) (–[CH 2 -CH(CH 3 )] n–), poly(vinyl chloride) (PVC) (–[CH 2 -CH(CH 3 )] n –), poly(vinylidene chloride) (–(CH 2 -CCl 2 ) n –), polystyrene (PS) (–[CH 2 -CH(C 6 H 5 )] n –), polyacrylonitrile (PAN) (–(CH 2 -CHCN) n –), polytetrafluoroethylene (PTFE) (–(CF 2 -CF 2 ) n –), poly(methyl methacrylate) (PMMA) (–[CH 2 -C(CH 3 )CO 2 CH 3 n –), poly(vinyl acetate) (PVAc) (–(CH 2 -CHOCOCH 3 ) n –), cis - polyisoprene (–[CH 2 -CH=C(CH 3 )-CH 2 n –) and polychloroprene (cis + trans) (–[CH 2 -CH=CCl-CH 2 n –), to name but a few. In some embodiments, the chains of the base polymer can be configured as homopolymers. In some other embodiments, the chains of the base polymer can be configured as copolymers. When configured as a copolymer, the chains of the base polymer can be configured to have one of various forms, including but not limited to, for example, statistical copolymers, alternating copolymers, block copolymers, and graft copolymers incorporating monomer units of the various polymers described above.

[0096] Among other factors, a particular polymer can be selected based on the deposition chemistry of the inorganic material to be incorporated into the base polymer material. For example, in various embodiments, the polymer chains of the base polymer units can include various functional groups, such as carbonyl, hydroxyl, and pyridyl, which are suitable for reacting with metal precursors that can be used to form the inorganic material, as will be described in further detail below. As an example, when the deposition chemistry includes Al(CH 3 ) 3 (TMA) as a metal precursor and H 2 ​​​O as an oxidation precursor for forming Al 2 O 3 When, PMMA can be included in the polymeric material such that the carbonyl group of PMMA can react with TMA to form an Al-OH species, which then reacts with H 2 O in a hydrolysis reaction to form Al 2 O 3 Other examples will be described in more detail below.

[0097] In various embodiments, the base polymer can be photosensitive or photoreactive. The base polymer can include a photoresist or be used as a photoresist. In some embodiments, the photoresist can be a positive photoresist, where the portions exposed to light become soluble in a photoresist developer, while the unexposed portions remain insoluble in the photoresist developer. In some other embodiments, the photoresist can be a negative photoresist, where the portions of the photoresist exposed to light become insoluble in the photoresist developer, while the unexposed portions are dissolved by the photoresist developer.

[0098] In some embodiments, when included, the photoresist in the base polymer can be a photopolymerizable photoresist, which can include, for example, allyl monomers, which are configured to generate free radicals when exposed to light, which in turn initiate the photopolymerization of the monomers to generate a polymer. When configured as a negative resist, the photopolymerizable photoresist can include, for example, methyl methacrylate. When included, in some other embodiments, the photoresist in the base polymer can be a photo-decomposable photoresist, which is configured to generate hydrophilic products upon light exposure. When configured as a positive resist, the photo-decomposable photoresist can include, for example, azide quinone, such as N-dimethylbenzene quinone (DQ). When included, in some other embodiments, the photoresist in the base polymer can be a photo-crosslinkable photoresist, which is configured to crosslink chain by chain when exposed to light to generate an insoluble network.

[0099] Still referring to Figure 10 , according to various embodiments, the inorganic material incorporated into the optical structure 1008 can include insulating materials, such as, for example, metal oxides or metal nitrides. In some embodiments, the inorganic material includes oxides, nitrides, or oxynitrides of one or more transition metals, the one or more transition metals including but not limited to Al, Zn, Zr, Hf, Ti, and Ta. For example, the inorganic material can include alumina, zinc oxide, zirconia, hafnia, titanium oxide, tantalum oxide, and combinations thereof, to name a few.

[0100] As described herein, when the inorganic material includes an oxide, it can be stoichiometric or sub-stoichiometric. For example, alumina can be in the stoichiometric form of Al 2 O 3 , or it can be in the sub-stoichiometric form of AlO x , where x is less than the stoichiometric value of 1.5. Additionally, as described herein, the oxide of a metal can include other metals. For example, it can include alumina as part of aluminum hafnium oxide (AlHfO x ). Thus, the material can include two different metals.

[0101] According to an embodiment, the inorganic material can be selected based on its bulk refractive index. The refractive index of the inorganic material can be higher than the refractive index of the substrate. The refractive index of the inorganic material can be, for example, greater than 1.7, 2.0, 2.3, 2.6, 3.0, or have a value within the range defined by these values or can be outside these ranges. In some embodiments, the inorganic material can be a stoichiometric material selected based on its bulk refractive index. For example, the inorganic material can be stoichiometric alumina having a refractive index of 1.66, stoichiometric zinc oxide having a refractive index of 1.95, stoichiometric zirconia having a refractive index of 1.95, stoichiometric hafnium oxide having a refractive index of 2.09, stoichiometric titanium oxide having a refractive index of 2.35, or a combination thereof, to name a few. In some other embodiments, the inorganic material can be a sub-stoichiometric inorganic material having a refractive index greater than that of the corresponding stoichiometric inorganic material. For example, by reducing the oxygen content, the refractive index of the metal oxide can be increased by 2%, 5%, 10%, 20%, or 30% or any percentage within the range defined by these values. In some other embodiments, the inorganic material can be a mixture of inorganic materials having a refractive index between the refractive indices of the component inorganic materials. For example, the refractive index of a ternary metal oxide can be adjusted to be between the refractive indices of the component binary metal oxides by adjusting the relative fractions.

[0102] In some embodiments, the optical structure 1008 has a refractive index between that of the base polymer material and the inorganic material incorporated therein. In various embodiments, the second refractive index of the optical structure including the optical material is greater than 1.7, 1.8, 1.9, 2.0, or 2.1 and is at least 0.2, 0.4, 0.6, 0.8, or 1.0 greater than the first refractive index of the substrate. However, the embodiments are not limited thereto, and the second refractive index can be equal to or less than the first refractive index.

[0103] The base polymer material of the optical structure 1008 can incorporate inorganic materials in various configurations therein. In the illustrated embodiment, the optical structure 1008 includes a base polymer region 1008a and an infiltration region 1008b infiltrated by the inorganic material. In the illustrated embodiment, the inorganic material is incorporated into the surface region of the optical structure 1008 such that each optical structure 1008 has a base polymer region 1008a and an infiltration region 1008b. The base polymer region 1008a includes a core region substantially free of inorganic material, and the infiltration region 1008b includes a surface region infiltrated by the inorganic material.

[0104] According to an embodiment, the infiltration region 1008b has a width, depth, or thickness greater than about 1 nm, 10 nm, 20 nm, 50 nm, 100 nm, 200 nm, 300 nm or a thickness within the range defined by these values or a thickness that may exceed these ranges.

[0105] In some embodiments, the base polymer region 1008a is substantially free of inorganic material. In some cases, based on the total volume of the base polymer region 1008a, the base polymer region 1008a has less than 40%, 30%, 20%, 10%, 5%, 1%, 0.5%, or 0.1% (or any range defined by these values) of inorganic material. In contrast, the infiltration region 1008b is substantially infiltrated by the inorganic material. In some cases, based on the total volume of the infiltration region 1008b, the infiltration region 1008b has more than 40%, 50%, 60%, 70%, 80%, or 90% (or any range defined by these values) of inorganic material.

[0106] The diffraction grating 1000 has an optical structure 1008, and the optical structure 1008 is arranged such that adjacent structures in the periodically repeating optical structure 1008 are separated by a space 1012. In the illustrated embodiment, the surface of the substrate in the space 1012 does not have the base polymer material or the inorganic material formed thereon. This is because the base polymer material can be completely removed between adjacent structures in the base polymer structure before incorporating the inorganic material, such that the surface of the substrate is exposed in the resulting space 1012 between adjacent structures of the periodically repeating base polymer. Subsequently, since no functional groups suitable for adsorbing or chemisorbing the metal precursor for forming the inorganic material are formed on the exposed surface of the substrate, no inorganic material is formed thereon or the inorganic material is not incorporated into the substrate 1004. As a result, the surface of the substrate in the space 1012 does not have the base polymer material or the inorganic material formed thereon. The process is described in more detail below with respect to Figures 14A - 14B This process is described in more detail below.

[0107] However, as described in detail below, other embodiments are possible. In other embodiments, adjacent structures of the periodically repeating optical structure 1008 are separated by spaces 1012, where a layer of polymeric material is formed on the surface of the substrate in the spaces ( Figure 15B and 16B ), in which an inorganic material is incorporated, as described in detail with respect to Figures 15A - 15B and 16A-16B. In these embodiments, prior to incorporating the inorganic material, the base polymeric material is removed incompletely or partially between adjacent structures in the periodically repeating base polymeric structure such that the surface of the substrate remains covered by a thin layer of the base polymer in the spaces 1012 between adjacent structures in the protruding base polymeric structure ( Figure 15A and 16A ). Subsequently, the surface of the protruding base polymeric structure and the surface of the polymeric layer between adjacent structures in the protruding base polymeric structure are exposed to precursors to incorporate the inorganic material. For example, the incorporation of the inorganic material can be attributed to the presence of functional groups in the base polymeric structure that adsorb or chemisorb metal precursors and to subsequent reactions between the metal precursors and oxidation precursors to form the inorganic material in the optical structure 1008. In some embodiments, the layer of polymeric material formed in the spaces can have the entire thickness or a portion of the thickness incorporated with the inorganic material. These processes are described in detail below with respect to Figures 15A - 15B and 16A-16B.

[0108] Method of manufacturing an optical element formed from a polymer - based optical structure incorporating an inorganic material

[0109] Described below is a method of manufacturing a polymer-based optical element that includes a polymer-based optical structure in which an inorganic material is incorporated, e.g., a diffraction grating 1000 ( Figure 10 ). Referring to Figure 11 , method 1100 includes providing 1104 a substrate having a first refractive index and being transparent in the visible spectrum. The method further includes forming 1108 on the substrate a periodically repeating base polymeric structure. The method further includes 1112 exposing the substrate to a metal precursor and then to an oxidation precursor. The exposing of the substrate is performed at a pressure and temperature such that an inorganic material including the metal is incorporated into the periodically repeating base polymeric structure, thereby forming a pattern of a periodically repeating optical structure configured to diffract visible light, wherein the optical structure has a second refractive index greater than the first refractive index.

[0110] Referring to Figure 11 , a substrate having a first refractive index and being transparent in the visible spectrum is provided 1104. This can include, for example, providing a substrate 1004 as described above with respect to Figure 10 .

[0111] Still referring to Figure 11 , a periodically repeating basic polymer structure is formed on a substrate. As described below, suitable processes including, for example, a lithography process ( Figures 12A - 12C ) or a nanoimprint process ( Figures 13A - 13C ) can be used to form the polymer structure. In some embodiments, as described with respect to Figures 12A to 12C , forming a periodically repeating optical structure on a substrate can be performed by depositing a suitable polymer material as described above with respect to Figure 10 and then patterning using lithography and etching processes. In some other embodiments, as described with respect to Figures 13A - 13C , forming a periodically repeating optical structure on a substrate can be performed by depositing a suitable polymer material as described above with respect to Figure 10 and then patterning using nanoimprint technology.

[0112] Figures 12A - 12C Cross-sectional views of intermediate structures 1200A - 1200C at various stages of manufacturing a periodically repeating basic polymer structure using a lithography process according to embodiments are shown, respectively. Referring to Figure 12A of the intermediate structure 1200A, the method includes providing a substrate 1004. The substrate 1004 includes an optically transmissive material having a first refractive index (n 1 ) and various other possible material properties such as those described above with reference to Figure 10 . The method further includes forming a basic polymer layer 1208 on the substrate 1004 having a refractive index n 2 initial and various other possible material properties such as those described above with reference to Figure 10 . When patterned, the basic polymer layer 1208 is suitable for forming a periodically repeating basic polymer structure such as those described above with reference to Figure 10 .

[0113] In some embodiments, the basic polymer layer 1208 is formed of a single layer that provides functional groups for subsequent adsorption, chemisorption, or reaction of metal precursors. The basic polymer layer 1208 also serves as a photoresist that can be lithographically patterned by exposure / development and subsequent etching. The basic polymer layer 1208 can be a single layer that serves both of these functions. However, the design is not limited thereto, and in some other embodiments, the basic polymer layer 1208 can include multiple layers, including a photoresist layer formed on a separate active polymer layer having functional groups for adsorption, chemisorption, or reaction of metal precursors. That is, for example, when a single basic polymer layer 1208 cannot adequately serve as a photoresist and does not provide functional groups for adsorbing, chemisorbing metal precursors, or reacting with metal precursors, the basic polymer layer 1208 can include a multilayer structure.

[0114] Depending on the design, the base polymer layer 1208 can be deposited by spin coating followed by post-baking.

[0115] Referring Figure 12B to the intermediate structure 1200B of , after deposition and post-baking, the method includes patterning the base polymer layer 1208 by selectively exposing a portion of the base polymer layer 1208 to a pattern of light generated by a photomask 1216. As shown, the photomask 1216 can be a positive photomask suitable for a positive photoresist and can be configured to allow light to pass through the regions where the base polymer layer 1208 is to be retained. When the photomask 1216 is a negative photomask suitable for a negative photoresist, the photomask can be configured conversely to allow light to pass through the regions from which the base polymer layer 1208 is to be removed.

[0116] Exposure to light 1212 (e.g., coherent UV light or an electron beam) causes chemical changes, such as polymerization crosslinking in the base polymer layer 1208 (e.g., including a photoresist), which allows selective removal of the exposed portions of the base polymer layer 1208 using a developer solution for a base polymer layer 1208 that includes or serves as a positive photoresist, or allows selective removal of the unexposed portions of the photoresist using a developer solution for a base polymer layer 1208 that includes or serves as a negative photoresist.

[0117] Referring Figure 12C to the intermediate structure 1200C of , after selective removal, the resulting periodically repeating base polymer structure 1220a / 1220b remains on the substrate 1004 and thus serves as a template for subsequent infiltration of an inorganic material. The base polymer structure 1220a can be a set of base polymer structures elongated in a first direction, e.g., the y direction. Optionally, the base polymer structure 1220b can be a set of base polymer structures elongated in a second direction, e.g., the x direction. The base polymer structure can also include base polymer structures elongated in the first direction and base polymer structures elongated in the second direction. Other configurations are possible.

[0118] Figures 13A - 13C Cross-sectional views of the intermediate structures 1300A - 1300C at various stages of manufacturing a periodically repeating base polymer structure using a nanoimprint process are shown, respectively. In the example shown, the method of forming the intermediate structure 1300A is similar to the method of forming Figure 12A the intermediate structure 1200A of . However, the methods of forming the intermediate structures 1300B and 1300C of Figure 13B and 13C respectively are different from the methods of forming the intermediate structures 1200B and 1200C of Figure 12B and 12CThe methods for the intermediate structures 1200B and 1200C are different, and the differences are described below.

[0119] Referring to Figure 13B the intermediate structure 1300B, which is different from the method referred to above Figure 12B In the example shown, instead of selectively exposing and removing portions of the base polymer layer 1208 by using light or an electron beam and a developer solution to pattern the base polymer layer 1208, a nanoimprint template 1316 or a nanoimprint mold having a predetermined topological pattern according to the formation of a periodically repeating base polymer structure is brought into contact with the base polymer layer 1204. Subsequently, the template 1316 is pressed into the base polymer layer 1208, thereby transferring the pattern of the template 1316 into the softened base polymer layer 1208, which may include a thermoplastic polymer at a certain temperature (e.g., above the glass transition temperature of the base polymer layer 1208). After cooling, the template 1316 is separated from the base polymer layer 1208, and the patterned periodically repeating base polymer structure 1220a / 1220b remains on the substrate 1004. In some other methods, after being pressed into the base polymer layer 1208, the base polymer layer 1208 is hardened by crosslinking under ultraviolet light.

[0120] Referring again to Figure 11 , the method of manufacturing a polymer optical element incorporating an inorganic material further includes exposing the substrate to a metal precursor and then to an oxidation precursor, wherein the exposure of the substrate is performed under pressure and temperature such that an inorganic material including the metal is incorporated into the periodically repeating base polymer structure, thereby forming a pattern of a periodically repeating optical structure configured to diffract visible light, wherein the optical structure has a second refractive index greater than a first refractive index. Hereinafter, referring to Figures 14A - 14B , 15A - 15B and 16A - 16C, different ways of exposing the substrate to incorporate an inorganic material into the periodically repeating base polymer structure are described.

[0121] Figure 14A shows an intermediate structure 1400A including a periodically repeating base polymer structure 1204 manufactured using, for example, a method similar to that shown above with respect to Figures 12A - 12C and Figures 13A - 13C . Thus, the periodically repeating base polymer structure 1204 formed on the substrate 1004 is similar to the periodically repeating base polymer structure 1220a / 1220b shown above with respect to Figures 12A - 12C and Figures 13A - 13C . Figure 14B shows an intermediate structure 1400B that includes a periodically repeating optical structure 1008 in which an inorganic material is incorporated, as described above with respect toFigure 10 As described below, with reference to Figure 14A and 14B , a method for incorporating an inorganic material into a periodically repeating base polymer structure 1204 ( Figure 14A ) to form a periodically repeating optical structure 1008 ( Figure 14B ) will be described in detail.

[0122] Some process features used in atomic layer deposition (ALD) can be used to incorporate an inorganic material into a periodically repeating base polymer structure 1204 ( Figure 12A ) to form a periodically repeating optical structure 1008 ( Figure 12B ). In some aspects, ALD can be considered a type of chemical vapor deposition (CVD) process with self-limiting growth, which is controlled by dividing a chemical reaction into two separate half-reactions included in a growth cycle. The growth cycle for the ALD process can include four stages: (1) exposure of a first precursor, such as a metal precursor; (2) purging the reaction chamber; (3) exposure of a second precursor, such as an oxidation precursor; (4) further purging the reaction chamber. In the first stage of the ALD process, the first precursor reacts with sites on the substrate to form all or part of a molecular layer of the first precursor. In the second stage, an inert gas such as argon or N 2 can be used to purge and / or evacuate unreacted first precursor molecules to reduce, prevent, or minimize gas-phase reactions that may occur between the remaining first precursor and the subsequently introduced second precursor, which would prevent layer-by-layer growth of molecules. In the third stage, the second precursor is introduced into the purged chamber to react with the molecular layer of the first precursor, thereby producing a monolayer or submonolayer of the target material. The fourth stage includes purging / evacuating the residue of the second precursor to prepare for another growth cycle, and this process can be repeated until the desired thickness is reached.

[0123] As described above with respect to Figure 10 , the inorganic material incorporated into the optical structure 1008 can include metal compounds such as dielectrics including metals. The inorganic material can include, for example, metal oxides or metal nitrides, such as oxides, nitrides, or oxynitrides of one or more transition metals including Al, Zn, Zr, Hf, Ti, and Ta. The ALD growth cycle can thus include: (1) exposing the substrate to a metal precursor containing a transition metal; (2) purging the reaction chamber; (3) exposure of an oxidation precursor; (4) further purging the reaction chamber. The inorganic material can be produced by an oxidation process to produce, for example, metal oxides, metal nitrides, or other inorganic materials.

[0124] Advantageously, the use of ALD processes for incorporating inorganic materials has many benefits. For example, since the adsorption, chemisorption, or reaction of precursors provides control over the amount of material deposited at the monolayer or sub-monolayer level, the film thickness or amount of material deposited can be precisely controlled based on the number of reaction cycles. Additionally, since precursors in the gas phase can reach surfaces that are difficult or impossible to access using other deposition techniques, such as physical vapor deposition (PVD) or plasma-enhanced chemical vapor deposition (PECVD) techniques that depend on line-of-sight and / or aspect ratio, ALD can be a suitable method for depositing conformal thin films on three-dimensional surfaces. Further, since adsorption, chemisorption, or reaction can occur at relatively low temperatures (e.g., below 100 °C), ALD can be suitable for deposition on structures or surfaces with limited thermal budgets or heat capacity limits.

[0125] Accordingly, in a preferred embodiment, an inorganic material can be incorporated into the periodically repeating underlying polymer structure 1204 to form the periodically repeating optical structure 1008 in a reactor configured for ALD and / or using some of the process features used in ALD as described above.

[0126] Certain combinations of pressure, temperature, and time can be particularly suitable for forming the optical structure 1008, as described in detail below. Thus, according to an embodiment, exposing the substrate to one or both of a metal precursor and an oxidation precursor includes exposing using one or both of the metal precursor and the oxidation precursor at a total pressure and / or partial pressure and for a duration sufficient to saturate the exposed surface of the underlying polymer structure with one or both of the metal precursor and the oxidation precursor.

[0127] Return reference Figure 11, according to an embodiment, exposure 1112 is performed at a pressure greater than atmospheric pressure. Without being bound by any theory, the higher pressure can enhance the diffusion of the precursor before the reaction to form the inorganic material and / or enhance the diffusion of the inorganic material after formation. During exposure to the metal and / or oxidation precursor, one or both of the total pressure and the partial pressure can be adjusted or optimized. In different cases, the total pressure during exposure can be between about 10 mTorr and about 100 Torr, between about 50 mTorr and about 50 Torr, between about 100 mTorr and about 10 Torr, or any pressure within the range defined by these values or outside these ranges, such as between about 800 mTorr and about 5 Torr or between 1 Torr and 5 Torr. At the total pressure, the partial pressure of the precursor can be 2%, 5%, 10%, 20%, 50% of the total pressure or any pressure within the range defined by these values or outside these ranges, such as for example about 25 - 50 mTorr. The remaining partial pressure can be provided by one or more gases other than the precursor, such as an inert gas, such as argon and / or N 2 .

[0128] During the purge process, the total pressure can be maintained the same as or different from the total pressure during exposure to the precursor as described above.

[0129] Depending on the method, exposure 1112 can include exposing the periodically repeated base polymer structure 1204 to one or both of a metal precursor and an oxidation precursor for a duration greater than 1 second, 5 seconds, 10 seconds, 30 seconds, 60 seconds, 100 seconds, 500 seconds, or 1000 seconds, such as about 10 seconds to 400 seconds, or for a duration within any range defined by these values. Durations outside these ranges are also possible. Depending on the situation, the exposure time can be greater than the conventional exposure time used in conventional ALD that is sufficient to fill the deposition surface with the precursor. Such an exposure time can be less than 1 second. Without being bound by any theory, a longer exposure time can advantageously provide sufficient time for the precursor to diffuse into the base polymer structure 1204 before the formation of the inorganic material and / or provide sufficient time for the diffusion of the inorganic material after the formation of one or more monolayers of the inorganic material. In some cases, a portion of the exposure time may be sufficient to fill the surface with the precursor, while the remaining exposure time can be used for diffusing the precursor and / or the inorganic material. In some cases, the duration of the exposure is more than 10x, 20x, 50x, 100x, or 1000x or for a duration within any range defined by these values longer than the duration sufficient to fill the surface with the precursor. Values outside these ranges are also possible.

[0130] During the purge process, the purge time can be equal to or longer than the exposure time to the precursor described above, for example, longer than 2x, 5x, or 10x or any time within the range defined by these values. The purge time can also be outside of these ranges. Thus, the sub-periods t 1 、t 2 、t 3 and t 4 can have combinations of the durations described above. For example, t 1 、t 3 = 1 - 100 seconds or any of the above ranges and t 2 、t 4 = 5 - 500 seconds or any of the above ranges, where the sub-periods t 1 、t 2 、t 3 and t 4 correspond to the first exposure time for exposing the substrate to the metal precursor, the first purge time for purging the metal precursor, the second exposure time for exposing the substrate to the oxidation precursor, and the second purge time for purging the oxidation precursor.

[0131] Depending on the configuration and / or manufacturing method, exposure 1112 includes exposing a periodically repeating base polymer structure to one or both of a metal precursor and an oxidation precursor at a temperature below about 100 degrees Celsius. Relatively low temperatures can be employed to achieve the desired diffusion depth of the precursor and / or inorganic material, since increased pressure and longer exposure times can compensate for the lower temperature. According to an embodiment, the exposure can be performed at a temperature below 200 °C, 150 °C, 100 °C, 80 °C, 60 °C, 40 °C, or 20 °C or at any temperature within the range defined by these values. Temperatures outside of these ranges can be used, including temperatures above 100 °C.

[0132] Exposing the substrate to the metal precursor can include exposing it to a precursor containing a transition metal, such as a transition metal selected from the group consisting of aluminum, zinc, zirconium, hafnium, and titanium. For example, in order to incorporate transition metal oxides, which include aluminum oxide, zinc oxide, zirconium oxide, hafnium oxide, titanium oxide, tantalum oxide, and combinations thereof, the metal precursor for the first stage can include halides of the transition metal (i.e., metals bonded to F, Cl, Br, or I), alkyl compounds, and alkoxides.

[0133] Depending on the desired structure and / or method, the metal halide precursor can include aluminum chloride or aluminum iodide, zinc chloride or zinc iodide, zirconium chloride or zirconium iodide, hafnium chloride or hafnium iodide, titanium chloride or hafnium iodide, or tantalum chloride or tantalum iodide.

[0134] Depending on the desired structure and / or method, the metal precursor having oxygen bonded to the metal can include alkoxides (M-(O-CR)n), such as hafnium tert-butoxide Hf(OC4 H 9 ) 4 , wherein each alkoxy ligand is bonded to the metal atom through an O atom, and the metal precursor further includes a β-diketone complex (M=(O 2 C 3 R 3 ) n , such as Zr(thd) 4 , wherein each diketone ligand is bonded to the metal through two metal-oxygen bonds (the ligand "chelates" the metal center).

[0135] Depending on the desired structure and / or method, the precursor having nitrogen bonded to the metal may include metal alkylamides (M(NR 2 ) n ), such as hafnium dimethylamide, Hf(N(CH 3 ) 2 ) 4 and metal amidinates (M(N 2 CR 3 ) n ).

[0136] Organometallic precursors having a metal atom directly bonded to carbon can also be used. Such organometallic precursors can include: alkyl M(C x H y ) n , such as trimethylaluminum, Al(CH 3 ) 3 ; cyclopentadienyl, such as hafnium dimethyl dicyclopentadienyl, Hf(C 5 H 5 ) 2 (CH 3 ) 2 (mixed ligand precursor). Other precursors can be used.

[0137] Depending on the desired structure and / or method, exposing the substrate to an oxidation precursor can include exposing it to a precursor containing oxygen (O, O 2 ), ozone (O 3 ), water (H 2 O), hydrogen peroxide (H 2 O 2 ), nitrogen oxides (NO, N 2 O), ammonia (NH 4 ) or a combination thereof, according to the embodiment. Other precursors can be used, such as other oxidation precursors.

[0138] Combinations of different precursors can be used and can depend on which inorganic material is incorporated into the periodically repeating base polymer structure 1204. For example, aluminum oxide can be more easily deposited from trimethylaluminum and water or ozone, while aluminum nitride can be more easily made from aluminum dimethylamide, Al 2 (N(CH 3 ) 2 ) 6 and ammonia. For the ALD of hafnium oxide and hafnium oxynitride, hafnium ethylmethylamide, Hf(N(CH 3 )(C 2 H 5 )) 4 might be a suitable liquid precursor that combines high reactivity towards water, ozone, and ammonia, as well as sufficient volatility and stability.

[0139] Additionally, as described above with respect to Figure 10 , the polymer chains of the base polymer units can include various functional groups, such as carbonyl, hydroxyl, and pyridyl groups, which are configured to react with specific metal precursors to form inorganic materials. To provide an illustrative example, when the deposition chemicals include Al(CH 2 O 3 )(TMA) and H 3 ) 3 for forming Al 2 O and H 2 O, then PMMA can be included in the polymeric base material such that the carbonyl groups of PMMA react with TMA to form Al-OH species, which then react with H 2 O in a hydrolysis reaction to form Al 3 O, which is incorporated into the base polymer structure 1204. 2 O 3 Based on the foregoing, various parameters can be selected, including exposure time, purge time, total pressure or partial pressure, and substrate temperature, to control the diffusion of the precursors and / or inorganic materials to form the optical structure 1008, which includes a base polymer region 1008a and a penetrated region 1008b penetrated by the inorganic material. In some embodiments, the inorganic material is incorporated into the surface region of the optical structure 1008 such that each optical structure has a base polymer region 1008a that includes a core region of the optical structure where substantially no inorganic material is incorporated, and each optical structure further has a penetrated region 1008b that includes a surface region where the inorganic material is penetrated.

[0140] Reference Figure 14A and 14B

[0141] ​In addition, the diffusion of the precursor and / or the inorganic material can be controlled such that the width, depth, or thickness (H i -H f and / or W i -W f ) of the penetration region 1008b is greater than about 1 nm, 10 nm, 20 nm, 50 nm, 100 nm, 200 nm, 300 nm, or a thickness within the range defined by these values. Thicknesses outside of these ranges are also possible. Thus, the base polymer region 1008a can be substantially free of inorganic material. Based on the total volume of the base polymer region 1008a, the base polymer region can have less than 40%, 30%, 20%, 10%, 5%, or 1% inorganic material, or can have any percentage within any range defined by these values. Percentages outside of these ranges are also possible. In contrast, the penetration region 1008b is substantially penetrated by the inorganic material. Based on the total volume of the base polymer region 1008a, the penetration region 1008b can have greater than 40%, 50%, 60%, 70%, 80%, 90%, 95%, or 99% inorganic material, or can have any percentage within any range defined by these values. Percentages outside of these ranges are also possible.

[0142] However, the configuration is not limited thereto, and in some other configurations, substantially all of the volume of the periodically repeating base polymer structure 1204 is penetrated by the inorganic material such that after penetration, the base polymer structure 1204 has substantially no base polymer region 1008a that is free of inorganic material.

[0143] As described above, one or more exposure conditions affect the diffusion characteristics of the precursor and / or the inorganic material. Without being bound by any theory, in some embodiments, at least some of the precursor is diffused into the base polymer structure 1204 before the inorganic material is formed. For example, at least a portion of a monolayer of the metal precursor can be diffused into the polymer structure 1204 to a depth equal to or less than the depth of the penetration region 1008b to react, for example, with functional groups of the base polymer material in the polymer structure 1204. Thereafter, at least a portion of a monolayer of the oxidation precursor can be diffused into the base polymer structure 1204 to a depth equal to or less than the depth of the penetration region 1008b so as to react, for example, with the metal precursor to form at least a portion of the inorganic material within or beneath the surface of the periodically repeating base polymer structure 1204.

[0144] However, the configuration is not limited thereto. Without being bound by any theory, in some other embodiments, at least a portion of the inorganic material diffuses into the underlying polymer structure 1204 after formation. For example, after being formed at the surface of the underlying polymer structure 1204, at least a portion of a monolayer of the inorganic material can diffuse into the polymer structure 1204 to a depth equal to or less than the depth of the penetration region 1008b.

[0145] Still referring to Figure 14A and 14B , advantageously, the underlying polymer material forming the periodically repeating polymer structure 1204 has a composition, structure, and density such that, after incorporating the inorganic material under the various processing and material parameters as described above, the dimensions of the periodically repeating optical structure 1204 before incorporating the inorganic material and the periodically repeating optical structure 1008 after incorporating the inorganic material vary within a relatively limited amount. For example, for a design having a substantially rectangular cross-sectional shape such as the illustrated embodiment, the variation in one or both of the width and height is less than 30%, 20%, 10%, 5%, or 1%, or a percentage within the range defined by these values, although percentage variations outside of these ranges are also possible. The relatively small variation in the lateral dimensions is advantageous at least because it reduces the variation in critical dimensions due to processing.

[0146] According to some embodiments, a process sequence similar to thermal atomic layer deposition (ALD) is used to incorporate or penetrate the inorganic material into the underlying polymer structure 1204. Thermal ALD processes are depositions that are carried out without the use of plasma. In some other embodiments, plasma-enhanced atomic layer deposition (PE-ALD) is used to incorporate or penetrate the inorganic material. Whether to use thermal or PE-ALD can depend on the dimensions and aspect ratio of the periodically repeating underlying polymer structure 1204. For example, for an underlying polymer structure 1204 having a relatively high aspect ratio and / or a relatively small spacing between adjacent polymer structures 1204, in some cases, the plasma may not reach the deeper regions of the high aspect ratio underlying polymer structure 1204. In these cases, when using PE-ALD, different portions of the underlying polymer structure 1204 may be exposed to different amounts of plasma, resulting in non-uniform deposition, e.g., a thicker film is deposited near the upper regions of the underlying polymer structure 1204 compared to the deeper regions. Alternatively, thermal ALD may be more advantageous because thermal ALD may not depend on the ability of the plasma to reach the portion of the surface where it is deposited. However, in other cases, PE-ALD may be more desirable, e.g., to allow for lower temperature deposition because the plasma can lower the activation energy of the ALD reaction.

[0147] In the foregoing, example methods and apparatuses were described in which inorganic materials were combined with or infiltrated into the periodically repeating optical structure 1008 using methods related to ALD. However, the methods and apparatuses are not limited thereto. In some cases, for example, in cases where the inorganic material is formed before it diffuses into the underlying polymer structure 1204 and / or in cases where the dimensions of the underlying polymer structure 1204 and the spaces therebetween are large, other deposition techniques can be employed, for example, to achieve faster throughput. For example, in some cases, processes such as chemical vapor deposition (CVD) (including plasma-based CVD processes such as plasma-enhanced chemical vapor deposition (PECVD)) and heat-based CVD (such as low-pressure chemical vapor deposition (LPCVD)) can be used to infiltrate the inorganic material. In addition to other techniques, physical vapor deposition (PVD) and evaporation can also be used to infiltrate the inorganic material.

[0148] According to various embodiments, advantageously, inorganic materials are combined by selectively exposing the substrate to a metal precursor and an oxidation precursor relative to the exposed surface of the underlying polymer material of the exposed surface of the substrate. This is because, as described above, unlike the surface of the periodically repeating underlying polymer structure 1204, the surface of the substrate 1004 does not have functional groups suitable for adsorbing, chemisorbing, or reacting with the metal precursor. Therefore, based on the selectivity of the adsorption, chemisorption, or reaction of the metal precursor, variations of the periodically repeating optical structure can be formed, as described below with respect to Figure 14A / 14B, 15A / 15B, and 16A / 16B.

[0149] In Figure 14A and 14B the illustrated embodiments, when the periodically repeating underlying polymer structure 1204 is formed, adjacent structures in the periodically repeating underlying polymer structure are separated by a space 1012. Unlike the surface of the underlying polymer structure 1204, the surface of the substrate in the space 1012 does not have the underlying polymer material formed thereon. That is, before exposing the precursors for combining the inorganic material into the polymer structure 1204, the underlying polymer material is completely removed between adjacent structures in the underlying polymer structure 1204 such that the surface of the substrate is exposed in the space 1012. Subsequently, since the exposed surface of the substrate does not have functional groups suitable for adsorbing, chemisorbing, or reacting with the metal precursor, no inorganic material is formed thereon.

[0150] According to alternative embodiments, referring respectively to Figure 15A , 16A the intermediate structures 1500A, 1600A, and Figure 15B , 16BThe intermediate structures 1500B and 1600B are described, which involve incorporating inorganic materials into the periodically repeating basic polymer structure 1204 ( Figure 15A , 16A ) to form the periodically repeating optical structure 1008 ( Figure 15B , 16A ). The various manufacturing processes for obtaining the intermediate structures 1500A, 1600A and 1500B, 1600B, which are similar to the manufacturing processes for obtaining the intermediate structures 1400A ( Figure 14A ) and 1400B ( Figure 14B ) respectively, are omitted here, and the differences are described. In the illustrated embodiment, different from the embodiment shown with respect to Figure 14A / 14B, forming the periodically repeating basic polymer structure 1204 includes forming adjacent structures in the periodically repeating basic polymer structure 1204 separated by the space 1012, and the space 1012 has a substrate surface on which the layers 1504 ( Figure 15A ), 1604 ( Figure 16A ) of the basic polymer material are formed. That is, before incorporating the inorganic material into the basic polymer structure 1204, the basic polymer material is incompletely or partially removed from between the substrate surfaces in the space 1012. As a result, in the space 1012 between the adjacent structures in the protruding periodically repeating basic polymer structure 1204, the surface of the substrate 1004 remains covered with the layer of the basic polymer material. Subsequently, the surfaces of the protruding periodically repeating basic polymer structure 1204 and the polymer layers 1504 ( Figure 15A ), 1604 ( Figure 16A ) on the substrate in the space 1012 are exposed to the precursor to incorporate the inorganic material. As described above, the incorporation of the inorganic material can be caused by the presence of functional groups that adsorb or chemisorb metal precursors in the basic polymer structure and the subsequent reaction between the metal precursor and the oxidation precursor. Alternatively, this incorporation can be caused by the formation of the inorganic material on the surface of the polymer material, which then diffuses into the periodically repeating basic polymer structure 1204 to form the periodically repeating optical structure 1008. As a result, the entire exposed surface incorporates the inorganic material, and the entire exposed surface includes the surface area in the protruding optical structure 1008 and the surfaces of the polymer layers 1508 ( Figure 15A ), 1608 ( Figure 16A ) on the substrate surface in the space 1012 between the adjacent structures in the optical structure 1008.

[0151] In some embodiments, as Figure 15A shown, the polymer material layer 1504 formed on the substrate surface in the space 1012 has a relatively low thickness. For example, its thickness is similar to or less than the thickness of the penetration region 1008b (Hi -H f and / or W i -W f ). In these embodiments, as Figure 15B shown, after penetration of the inorganic material, substantially the entire thickness of the polymer material layer 1508 in the space 1012 may (or may not) be combined with the inorganic material.

[0152] In some other embodiments, as Figure 16A shown, the polymer material layer 1604 formed on the substrate surface in the space 1012 has a relatively high thickness, for example, its thickness is greater than the thickness of the penetration region 1008b (H i -H f and / or W i -W f ). In these embodiments, after penetration of the inorganic material, a portion (less than the total thickness) of the thickness of the polymer material layer 1608 in the space 1012 is combined with the inorganic material in the surface region, as Figure 16B shown.

[0153] Advantageously, incorporating an inorganic material into the underlying polymer structure 1204 to form the optical structure 1008 results in an increase in the refractive index of the structure. According to an embodiment, the substrate 1004 has a first refractive index that is greater than the refractive index of air but less than a second refractive index of the optical structure 1008, for example, 1.5, 1.6, 1.7, 1.8, 1.9, or a value within the range defined by these values. Refractive indices outside of these ranges are also possible. In various embodiments, after incorporating the inorganic material, the second refractive index is greater than 1.7, 1.8, 1.9, 2.0, 2.1, or a value within the range defined by these values, and is at least 0.2, 0.4, 0.6, 0.8, 1.0, or a value within the range defined by these values greater than the first refractive index. Refractive indices and increases in refractive index outside of these ranges are also possible. Prior to incorporating the inorganic material, the periodically repeating underlying polymer structure 1204 may have a refractive index that is substantially lower than the final second refractive index of the optical structure 1008. For example, the refractive index of the underlying polymer structure 1204 prior to incorporating the inorganic material may be 1.3, 1.4, 1.5, 1.6, 1.7, or a value within the range defined by these values. For example, the refractive indices of PMMA and polystyrene at approximately 588 nm are approximately 1.49 and approximately 1.59, respectively. When incorporating an inorganic material having a refractive index greater than 1.7, 2.0, 2.3, 2.6, 3.0, or a value within the range defined by these values, the refractive index of the underlying polymer structure 1204 may, for example, increase to a value within the above range. Thus, the refractive index may increase by greater than approximately 0.1, 0.2, 0.3, 0.4, 0.5, or increase to a value within the range defined by these values. Refractive indices and increases in refractive index outside of these ranges are also possible.

[0154] Advantageously, incorporating inorganic materials into the underlying polymer structure 1204 to form the optical structure 1008 can result in an increase in mechanical stiffness, e.g., as measured by Young's modulus (E). According to embodiments disclosed herein, prior to incorporating the inorganic materials, the Young's modulus of the periodically repeating underlying polymer structure 1204 can be within about 1.0 GPa to about 5 GPa. For example, the Young's modulus of PMMA can be between about 2.5 and 3.5 GPa, e.g., about 3.1 GPa, while the Young's modulus of polystyrene can be between about 1.5 and 2.5 GPa, e.g., about 2.0 GPa. In various embodiments, after incorporating the inorganic materials, the Young's modulus of the periodically repeating underlying polymer structure 1204 can increase by more than 1 GPa, 2 GPa, 5 GPa, 10 GPa or increase by a value within the range defined by these values. The Young's modulus of the resulting optical structure 1008 incorporating the inorganic materials can be between about 2.5 GPa to about 17.5 GPa, between about 2.5 GPa to about 7.5 GPa, between about 7.5 GPa to about 12.5 GPa, between about 12.5 GPa to about 17.5 GPa. Young's modulus values outside of these ranges are also possible.

[0155] Although specific oxides and nitrides are disclosed herein as including inorganic materials, other materials are possible. Additionally, oxides and nitrides can be formed by oxidation processes such as those described herein or by other types of oxidation processes. Other materials can also be formed by oxidation processes. Other types of processes can also be used.

[0156] Optical element based on a geometric - phase metasurface comprising a polymer - based optical structure incorporating an inorganic material component

[0157] A metasurface can include surface structures capable of locally altering the polarization, phase, and / or amplitude of light in reflection or transmission. The metasurface can include an array of phase-shifting elements of sub-wavelength dimensions and / or sub-wavelength spacing, the pattern of which is configured to control the wavefront of light such that various optical functions can be derived therefrom, including beam shaping, lensing, beam bending, and polarization splitting. Factors that can be used to manipulate the wavefront of light include the material, size, geometry, and orientation of the surface structures. By arranging surface structures with different scattering characteristics on the surface, a spatially varying metasurface can be generated on which the optical wavefront can be substantially manipulated.

[0158] In conventional optical elements such as lenses and wave plates, the wavefront is controlled by the propagation phase in a medium much thicker than the wavelength. Different from conventional optical elements, metasurfaces use sub-wavelength-sized resonators as phase-shifting elements to induce phase changes in light. Since metasurfaces are formed by relatively thin and uniformly thick features, thin-film processing techniques such as semiconductor processing techniques and direct printing techniques such as nanoimprinting techniques can be used to pattern the metasurface across the surface.

[0159] As described above, polymer optical elements incorporating inorganic materials are relatively easy to fabricate while providing tunable refractive index and stiffness. As a result, polymer optical elements incorporating inorganic materials are excellent candidates for metasurface-based optical elements. In the following optical elements (e.g., diffraction gratings), a metasurface formed from a polymer-based optical structure incorporating inorganic materials is described.

[0160] Without being bound by any theory, when a light beam is incident along a closed cycle in the space of the polarization state of light, it can acquire a dynamic phase from the accumulated path length as well as from the geometric phase. The dynamic phase obtained from the geometric phase is attributed to the local change in polarization. Some optical elements that form a desired phase front based on the geometric phase can be referred to as Pancharatnam-Berry phase optical elements (PBOE). A PBOE can be composed of wave plate elements, and the orientation of the fast axis thereof depends on the spatial position of the wave plate element.

[0161] Without being limited by theory, by forming a metasurface with a half-wave plate formed by geometric phase optical elements (e.g., a PBOE whose fast axis orientation is formed according to the function θ(x,y)), an incident circularly polarized light beam can be completely transformed into an opposite helical light beam with a geometric phase equal to φ g (x,y) = + / - 2θ(x,y). By controlling the local orientation of the fast axis of the wave plate element between 0 and π, phase pickup / delay covering the entire range from 0 to 2π can be achieved while maintaining a relatively high and uniform transmission amplitude across the entire optical element, thereby providing the desired wavefront.

[0162] According to an embodiment, hereinafter, with reference to Figures 17A - 17H , a construction 1700 of a geometric PBOE based on a plurality of geometrically rotated wave plate elements is described, where each wave plate element includes a pattern of periodically repeated optical structures as described above ( Figure 10 , 14B, 1008 in 15B, 16B). In particular, a PBOE configured as a half-wave plate with a phase delay of π is described. In the illustrated embodiment, eight adjacent half-wave plate elements are arranged at equidistant intervals and are characterized by a constant angular difference Δθ in orientation between adjacent wave plates. However, it will be understood that fewer or more numbers of wave plate elements may be employed, with different angular differences Δθ in orientation between adjacent wave plates. For purposes of illustration, the next line schematically depicts the rotation of the polarization vector of an incident light beam having left circular polarization, i.e., the |LCP> state. The middle line shows a half-wave plate element composed of a plurality of periodically repeated optical structures similar to those described with reference to Figure 14B , 15B and 16B, whose fast axes are oriented at different angles θ with respect to the vertical axis. The top line schematically shows the corresponding polarization vectors of the light transmitted through the back of the wave plate element. The circular polarization and counterclockwise orientation angle of the fast axis of the wave plate are defined from the perspective of the light source.

[0163] Still referring to Figures 17A - 17H , an incident light beam can be described by polarization vectors 1704 and 1708 having equal amplitudes in the x and y directions respectively and a phase delay 1712 of π / 2 between the polarization vectors. In operation, the half-wave plate operates by shifting the phase between two perpendicular polarizations by π. The end result of this action is to flip the electric field pointing along the slow axis and maintain the electric field pointing along the fast axis. This action can also be regarded as an action in which the original polarization vector is flipped to its mirror image with the fast axis serving as a mirror. When considering a helical incident state in which the polarization vector rotates with time, it can be seen that the action of the wave plate is to switch the helicity from |LCP> to |RCP> and vice versa.

[0164] See Figure 17A 's bottom row. The electric field of the incident |LCP> light beam points upward on the positive y-axis at the initial time t = t 0 , as shown by vector 1704. After a quarter of the optical cycle (i.e., π / 2), the light points in the negative y direction, as shown by vector 1708. Figure 17A The action of the wave plate in the middle row of Figure 17A is to mirror vectors 1704 and 1708 to a mirror placed in the plane of the fast axis and the light propagation direction. The action of this mirror is to flip vector 1704 to the positive x direction and keep vector 1208 in its original direction. As a result, the |LCP> light beam is transformed into an |RCP> light beam.

[0165] Figures 17B to 17H Shows how the polarization vectors of the |LCP> light beam change when the fast axis of the wave plate is rotated by angles θ of π / 4, π / 2, 3π / 4, π, 5π / 4, 3π / 2, and 7π / 4 respectively. Regardless of the rotation angle, an |RCP> output light beam is produced. However, referring to Figure 17A, the phase delay generated by vectors 1704 and 1708 is given by . For example, as Figure 17E shows, when θ = π / 2, the action of the waveplate is to keep vector 1704 in the same direction while flipping vector 1708 from the negative y-direction to the positive y-direction. This generates an |RCP> beam, which is delayed by for the incident LCP light. Thus, for the half-waveplate shown, it will take half an optical cycle longer to reach the state shown in Figure 17A .

[0166] Thus, as an illustrative example, after passing through eight half-waveplate elements that are equally spaced and have a constant orientation angle difference (e.g., Δθ = π / 8) between adjacent ones, the transmitted RCP wave shows a constant phase difference between adjacent waveplates By using eight waveplate elements with fast-axis orientations varying between 0 and π, a phase delay / pickup covering the entire 0 - 2π range can be achieved. However, fabricating half-waveplate elements with high diffraction angles for visible light can be challenging. This is because, among other things, the diffraction angle depends on the length of the period of the periodically repeated waveplate elements, and due to space limitations, it may be difficult to form a relatively large number of half-waveplate elements within a relatively short length of this period.

[0167] In Figures 17A - 17H , for illustrative purposes, the half-waveplate shown includes eight equally spaced adjacent half-waveplate elements with a constant orientation angle difference Δθ between adjacent waveplates, where each waveplate element includes a pattern of a periodically repeated polymer-based optical structure incorporating an inorganic material. However, the embodiments are not limited thereto, and hereinafter, embodiments of diffraction gratings can be realized that cover the entire 0 - 2π range of phase delay / pickup with relatively high diffraction angles and diffraction efficiencies and uniformity of diffraction efficiency across a relatively wide range of incident angles, where there are fewer waveplates.

[0168] Applications of metasurfaces including PBOE include diffraction gratings, among various other applications, such as blazed gratings, focusing lenses, and axicons. As described herein, a blazed grating is capable of steering a light beam into several diffraction orders. The blazed grating can be configured to achieve a high grating efficiency at one or more diffraction orders (e.g., the +1 and / or -1 diffraction orders), resulting in the concentration of optical power in the desired diffraction order while the remaining power at other orders (e.g., the zero order) is low. In the present disclosure, various embodiments of metasurfaces including PBOE configured as diffraction gratings are described. According to various embodiments, the diffraction grating has a combination of desired optical properties, including one or more of a high diffraction angle, a high diffraction efficiency, a wide range of acceptance angles, and a highly uniform diffraction efficiency within the range of acceptance angles. These desired optical properties can be produced by a combination of various inventive aspects, including the material, size, and geometric configuration of the elements of the metasurface.

[0169] As described herein, visible light can include light having one or more wavelengths within various color ranges, which color ranges include the red, green, or blue color ranges. As described herein, red light can include light having one or more wavelengths within the range of about 620 - 780 nm, green light can include light having one or more wavelengths within the range of about 492 - 577 nm, and blue light can include light having one or more wavelengths within the range of about 435 - 493 nm. Thus, visible light can include light having one or more wavelengths within the range of about 435 nm - 780 nm.

[0170] As described herein, parallel, nominally parallel, or substantially parallel features, such as nanobeams, lines, line segments, or unit cells, refer to features having elongation directions that differ by less than about 10%, less than about 5%, or less than about 3%. Additionally, perpendicular, nominally perpendicular, or substantially perpendicular features refer to features having elongation directions that deviate from 90 degrees by less than about 10%, less than about 5%, or less than about 3% in the direction of extension.

[0171] As described herein, a structure configured to diffract light, such as a diffraction grating, can diffract light in a transmission mode and / or a reflection mode. As described herein, a structure configured to diffract light in a transmission mode refers to a structure in which the intensity of the diffracted light on the side of the structure opposite to the light incident side is greater than the intensity of the diffracted light on the same side of the structure as the light incident side, e.g., at least 10% greater, 20% greater, or 30% greater. Conversely, a structure configured to diffract light in a reflection mode refers to a structure in which the intensity of the diffracted light on the same side of the structure as the light incident side is greater than the intensity of the diffracted light on the side of the structure opposite to the light incident side, e.g., at least 10% greater, 20% greater, or 30% greater.

[0172] As described herein, a line, also referred to as a light beam or a nanobeam, is an elongated structure having a volume. As described above, the line or nanobeam of light is formed of a polymeric material in which an inorganic material is incorporated. It will be understood that the line is not limited to any particular cross-sectional shape. In some embodiments, the cross-sectional shape is rectangular.

[0173] Figure 18A and 18B respectively show a cross-sectional side view and a top view of a diffraction grating 1800 including a metasurface having a geometric phase optical element according to some embodiments. The diffraction grating 1800 includes a second-order geometric phase metasurface. Referring to Figure 18A the cross-sectional side view shown is Figure 18B a side view of the cross-section AA' shown. The diffraction grating 1800 includes a substrate 1804 having a surface on which a metasurface 1808 is formed that is configured to diffract light having a wavelength in the visible spectrum. The metasurface 1808 includes one or more first lines or nanobeams 1812 having a first orientation and generally extending in a first lateral direction (e.g., the y-direction) and a plurality of second lines or nanobeams 1816 having a second orientation and generally extending in a second direction (e.g., the x-direction). As described above, the one or more first lines or nanobeams 1812 and the plurality of second lines or nanobeams are formed of a polymeric material in which an inorganic material is incorporated. The one or more first lines or nanobeams 1812 may be considered to form a first set of nanobeams, while the second lines or nanobeams 1816 may be considered to form a second set of nanobeams. The one or more first lines 1812 and the second lines 1816 are disposed adjacent to each other in the second direction, and the first lines 1812 and the second lines 1816 are alternately repeated in the second direction with a period less than the wavelength of the light configured to be diffracted by the metasurface.

[0174] Preferably, the first lines 1812 all have the same width. In some embodiments, the second lines 1816 are laterally stacked in the y-direction between adjacent pairs of the one or more first lines 1812. Without being bound by theory, the one or more first lines 1812 and the second lines 1816 are oriented at an angle with respect to each other to preferably cause a phase difference between the visible light diffracted by the one or more first lines 1812 and the visible light diffracted by the second lines 1816, wherein the phase difference between the visible light diffracted by the one or more first lines 1812 and the visible light diffracted by the second lines 1816 is twice the angle.

[0175] In some embodiments, similar to the above reference Figures 17A - 17HFor the combination of wave plates shown, the phase difference caused by the relative orientation of one or more first lines 1812 with respect to a second line 1816 can vary between 0 and π, and the phase pick-up / delay can be implemented to cover the entire 0-2π range. In some embodiments, when one of the one or more first lines 1812 and the second line 1816 is rotated by π with respect to each other, e.g., rotated by π perpendicular to each other, a phase pick-up / delay of 2π can be achieved between the one or more first lines 1812 and the second line 1816. That is, different from Figure 18A - 1 8H, according to some embodiments, a phase pick-up / delay covering the entire 0-2π range can be implemented based on a two-level geometric phase metasurface having lines oriented in only two different directions. Advantageously, different from Figures 17A - 17H i.e., referring to Figures 17A - 17H the combination of wave plates shown, the footprint occupied by the shown metasurface 1808 is more compact and has a period less than or equal to the wavelength in the visible spectrum, which in turn enables a relatively high diffraction angle θ of the diffracted beams 1838, 1842.

[0176] The one or more first lines 1812 and the second line 1816 are formed of an optically transmissive material. As described herein and throughout the specification, a "transmissive" or "transparent" structure (e.g., a transmissive substrate) can allow at least some, e.g., at least 20, 30, 50, 70, or 90% of the incident light to pass through. Thus, in some embodiments, the transparent substrate can be a glass, sapphire, or polymer substrate. A "reflective" structure, e.g., a reflective substrate, can reflect at least some, e.g., at least 20%, 30%, 50%, 70%, 90%, or more of the incident light from it.

[0177] The one or more first lines 1812 and the second line 1816 can be described as protrusions, ridges, wrinkles, or nanowirings that protrude out of the page, extend along the page, and have a width. Additionally or alternatively, the separation regions between adjacent first lines 1812 and / or between adjacent second lines 1816 can be described as being recessed into the page and having spaced depressions, grooves, recesses, or trenches. In some embodiments, the first lines 1812 and the second line 1816 are elongated rectangular structures having a substantially rectangular cross-sectional shape in the yz plane. However, other embodiments are possible, where the first lines 1812 and the second line 1816 have cross-sectional shapes that can take on circular, elliptical, triangular, parallelogram, rhombus, trapezoid, pentagon, or any suitable shape.

[0178] In the following, various configurations including the dimensions and geometric arrangements of one or more first lines 1812 and second lines 1816 are described, the combined effect of which is to generate a grating based on a geometric phase optical element having desired optical properties described herein, the desired optical properties including one or more of a relatively high diffraction angle, a relatively high diffraction efficiency, a relatively wide range of acceptance angles, and a relatively uniform efficiency within the acceptance angle range.

[0179] Still referring to Figure 18A and 18B , in operation, when an incident beam 1830 of, for example, visible light is incident on the metasurface 1808 at an incident angle α measured with respect to a plane (e.g., the yz plane) perpendicular to the surface 1804S and extending in a direction parallel to the first line 1812, the grating 1800 partially transmits the incident light as a transmitted beam 1834 and partially diffracts the incident light as a diffracted beam 1842 of the +1 order diffracted at a diffraction angle θ 1 and a diffracted beam 1838 of the -1 order diffracted at a diffraction angle θ 2 , where the diffraction angles are measured with respect to the same plane (e.g., the yz plane) used to measure α. When one or both of the diffracted beams 1838 and 1842 are diffracted at a diffraction angle exceeding a critical angle θ TIR so as to undergo total internal reflection in a substrate 1804 configured as a waveguide, the diffracted beams 1838 and 1842 propagate along the x-axis in their respective opposite directions under total internal reflection (TIR) until the beams reach the OPE / EPE 1846, which may correspond to the light distribution elements 730, 740, 750 and the coupled output optical elements 800, 810, 820 ( Figure 9B ).

[0180] Without being bound by any theory, when the first lines 1812 and second lines 1816 with sub-wavelength feature sizes support leaky mode resonances, they can confine light, thereby causing a phase delay in the scattered light waves generated under TE and TM illumination. It has been found that the effectiveness of confining light in one or more of the first lines 1812 and second lines 1816 can be due to waveguides configured to act as resonators, and the resulting diffraction efficiency may depend, among other factors, on the material refractive indices and sub-wavelength dimensions of the first lines 1812 and second lines 1816.

[0181] Thus, in some embodiments, the first lines 1812 and / or the second lines 1816 are formed of a material having a relatively high refractive index. Thus, as described above, according to an embodiment, after combining with an inorganic material, the first lines 1812 and / or the second lines 1816 have a second refractive index greater than 1.7, 1.8, 1.9, 2.0 or 2.1 and at least 0.2, 0.4, 0.6, 0.8 or 1.0 greater than the first refractive index.

[0182] Continuing reference Figure 18A and 18B , in addition to being formed from the various materials described above, one or more first lines 1812 and second lines 1816 have a specific combination of dimensions to act as resonators of sub - wavelength dimensions that induce a phase shift of light.

[0183] In various embodiments, the W of the first line 1812 nano1 and the W of the second line 1816 nano2 each is less than the wavelength of the light that the metasurface 1808 is configured to diffract, and preferably less than the wavelengths in the visible spectrum. In some embodiments, each of W nano1 and W nano2 is in the range of 10 nm to 1 μm, 10 nm to 500 nm, 10 nm to 300 nm, 10 nm to 100 nm, or 10 nm to 50 nm, such as 30 nm. According to some embodiments, each of one or more first lines 1812 has the same width W nano1 . According to some embodiments, each of the second lines 1816 has the same width W nano2 . According to some embodiments, one or more first lines 1812 and second lines 1816 have the same width, that is, W nano1 = W nano2 . However, in some other embodiments, W nano1 and W nano2 may be substantially different. Additionally, in some embodiments, different lines among one or more first lines 1812 and / or different lines among the second lines 1816 may have different widths.

[0184] According to some embodiments, adjacent lines among one or more first lines 1812 in the second direction are spaced apart by a constant interval s 1 . Additionally, one of one or more first lines 1812 and one of the second lines 1816 that are adjacent to each other in the second direction are spaced apart by a constant interval s 2 . According to some embodiments, one or both of s 1 and s 2 are less than the wavelength that the metasurface 1808 is configured to diffract. Additionally, the first lines 1812 and the second lines 1816 have heights h nano1 and h nano2 respectively. The intervals s 1 , s 2 as well as the heights h nano1 and h nano2A specific combination is used to obtain an expected range (Δα) of the incident angle α, sometimes referred to as the acceptance angle or the field of view (FOV) range. As described herein, the expected range Δα can be described by an angular range spanning negative and positive values of α, outside of which the diffraction efficiency is reduced by more than 10%, 25%, or more than 50% or more than 75% relative to the diffraction efficiency at α = 0. For example, in the case where a uniform diffracted light intensity is desired within Δα, it is desired to have such a Δα that the diffraction efficiency is relatively flat within Δα. Referring again to Figure 18A , the incident light beam 1830 is incident on the surfaces of the metasurface 1808 and the waveguide 1804 at an angle α with respect to the surface normal (e.g., the yz plane). According to some embodiments, as described above, Δα is associated with the angular bandwidth for the metasurface 1808 such that the light beam 1830 within Δα is effectively diffracted by the metasurface 1808 at a diffraction angle θ with respect to the surface normal (e.g., the yz plane). In particular, when θ is θ TIR or more than θ TIR , the diffracted light propagates within the substrate 1804 under total internal reflection (TIR).

[0185] It has been found that Δα can depend on the shadow effect created by adjacent lines in one or more first lines 1812 in the second direction and adjacent lines in a second line 1816 in the first direction. That is, when the incident light beam 1830 is incident at an incident angle α greater than a specific value, the incident light beam directed at the feature may be blocked by adjacent features. For example, Δα can be associated with the arctangent of s 1 / h nano1 , s 2 / h nano1 and / or s 2 / h nano1 . In various embodiments, the ratio s 1 / h nano1 , s 2 / h nano1 and / or s 2 / h nano1 is selected such that Δα exceeds 20 degrees (e.g., + / - 10 degrees), 30 degrees (e.g., + / - 15 degrees), 40 degrees (e.g., + / - 20 degrees) or 50 degrees (e.g., + / - 25 degrees), or within an angular range defined by any of these values. The desired ratio s 1 / h nano1 , s 2 / h nano1 and / or s 2 / h nano1 can be achieved, where, for example, s 1 and s 2Each of which is in the range of 10 nm to 1 μm, 10 nm to 300 nm, 10 nm to 100 nm, or 10 nm to 50 nm, for example 30 nm. Of course, this can be achieved by having h nano1 and h nano2 with correspondingly relatively low values to achieve s 1 and s 2 relatively low values.

[0186] Advantageously, the relatively high refractive index (n 2 ) of the material of one or more first lines 1812 and / or second lines 1816 according to some embodiments allows for a relatively small thickness or height. Thus, in various embodiments, the first line 1812 and the second line 1816 have h nano1 and h nano2 , which, according to some embodiments, depends on n 1 and can be in the range of 10 nm to 1 μm, 10 nm to 500 nm, 10 nm to 300 nm, 10 nm to 100 nm, or 10 nm to 50 nm, for example 107 nm. For example, h nano1 and h nano2 can be 10 nm to 450 nm when n 2 is greater than 3.3, and can be 10 nm to 1 μm when n 1 is 3.3 or less. As another example, the height of the first line 1812 and the second line 1816 can be 10 nm to 450 nm.

[0187] According to various embodiments, a combination of s 1 and W nano1 can be selected such that the pitch (p nano1 ) of one or more first lines 1812, defined as the sum of s 1 and W nano1 , has a value that is the sum of W nano1 selected from the range of 10 nm to 1 μm, 10 nm to 500 nm, 10 nm to 300 nm, 10 nm to 100 nm, or 10 nm to 50 nm and s 1 selected from the range of 10 nm to 1 μm, 10 nm to 300 nm, 10 nm to 100 nm, or 10 nm to 50 nm, for example p nano1 = 95.5 nm.

[0188] Of course, relatively small values of s 1 and s 2 can be achieved, and h nano1 and h nano2 have relatively small values. Advantageously, materials with a relatively high refractive index n 1Materials are used to form one or more first lines 1812 and / or second lines 1816, and s can be obtained. 1 s 2 h nano1 and h nano2 relatively small values can be obtained. This is because, as the inventors have found, h nano1 and h nano2 may be inversely proportional to the bulk refractive index of the material forming the first line 1812 and the second line 1816. Therefore, for a polymer-based optical structure having the refractive index as described above, in various embodiments, h nano1 and h nano2 can be in the ranges of 500 nm to 1 μm, 300 nm to 500 nm, 100 nm to 300 nm, and 10 nm to 100 nm respectively. Thus, through the materials of one or more first lines 1812 and second lines 1816 having a high bulk refractive index n 1 and the corresponding dimensions s 1 s 2 h nano1 and h nano2 a specific combination, the total pitch Λ a can also be correspondingly reduced, which in turn increases the diffraction angle θ, as further described below.

[0189] Preferably, h nano1 and h nano2 are substantially equal, which may be advantageous for manufacturing. However, the embodiments are not limited thereto, and h nano1 and h nano2 can be substantially different.

[0190] In various embodiments, the first line 1812 and / or the second line 1816 are formed of a material whose bulk refractive index (n 2 bulk) is higher than the refractive index n 1 of the substrate 1804; that is, n 2 bulk > n 1 . In some embodiments, the substrate 1804 can be configured as a waveguide and can correspond to waveguides 310, 300, 290, 280, 270 ( Figure 6 ) and / or waveguides 670, 680, and 690 ( Figure 9A ). In such applications, the substrate preferably has a refractive index between that of air but less than n 1 bulk, such as 1.5, 1.6, 1.7, 1.8, 1.9 or higher but less than n 2 bulk, which can provide benefits for increasing Δα of a display that forms an image by outputting light from the substrate 1816.

[0191] Still referring to Figure 18A and18B , the metasurface 1808 can be described as forming a plurality of metasurface unit cells 1820 that repeat at least in the x-direction. As described herein, the metasurface unit cell 1820 can be defined as a footprint having a minimum repeating dimension in the x-direction, which includes one or more first lines 1812 and second lines 1816. As an example, each unit cell 1820 spans a unit cell width 1820a measured from the left vertical side of the left line of the first line 1812 in one unit cell 1820 to the left vertical side of the left line of the first line 1812 in the immediately adjacent unit cell 1820, and in the illustrated embodiment, thus includes a pair of first lines 1812 and a column of second lines 1816 stacked in the y-direction.

[0192] As described herein, the lateral dimension of the metasurface unit cell 1820 or the period of the repeating unit of the unit cell 1820 can be referred to herein as the unit cell pitch Λ a . The pitch Λ a repeats at least twice at regular intervals across the waveguide 1804 in the x-direction. In other words, the unit cell pitch Λ a can be the distance between the same points of directly adjacent unit cells 1820. In various embodiments, Λ a can be less than the wavelength at which the grating 1800 is configured to diffract, and can be less than the wavelength in the range of about 435 nm - 780 nm or any wavelength. In some embodiments configured to diffract at least red light, Λ a can be less than the wavelength in the range of about 620 - 780 nm (or any wavelength). In some other embodiments configured to diffract at least green light, Λ a can be less than the wavelength in the range of about 492 - 577 nm (or any wavelength). In some other embodiments configured to diffract at least blue light, Λ a can be less than the wavelength in the range of about 435 - 493 nm (or any wavelength). Optionally, according to various embodiments, Λ a can be in the range of 10 nm to 1 μm, including 10 nm to 500 nm or 300 nm to 500 nm. It should be understood that each of the metasurfaces disclosed herein can be used to diffract light and can be part of the display system 250 ( Figure 6 ), and the display system 1000 can be configured to direct light to the metasurface having a narrowband wavelength. Preferably, Λ a used for a given metasurface is less than the minimum wavelength of the wavelength band to which the light source of the display system is configured to direct light to the metasurface.

[0193] It has been found that in some embodiments, Λ a can have a ratio less than mλ / (sinα + n 2the value of sinθ), where m is an integer (e.g., 1, 2, 3, …) and α, n 2 and θ respectively have the values described in other places in the specification. For example, α can be within a range Δα greater than 40 degrees, n 2 can be within the range of 1 - 2, and θ can be within the range of 40 - 80 degrees.

[0194] In some embodiments, Λ a can be substantially constant across the surface 1804S of the grating 1800 formed by multiple unit cells. However, the embodiments are not limited thereto, and in some other embodiments, Λ a can vary across the surface 1804S.

[0195] Still referring to Figure 18B , in some embodiments, the length of each of the second lines 1816 is at least two, three, four, or more times shorter than the length of each of one or more of the first lines 1812. However, embodiments where the second lines 1816 are longer than one or more of the first lines 1812 are possible. According to various embodiments, one or more of the first lines 1812 can have a length L within the range of 200 μm - 5 mm, 200 μm - 1 mm, or 1 mm - 5 mm 1 . According to various embodiments, the second lines 1816 can have a length L within the ranges of 100 nm to 500 nm, 100 nm to 300 nm, and 300 nm to 500 nm 2 . In some embodiments, one or more of the first lines 1812 can have a length L 1 , and this length L 1 corresponds to the total lateral dimension of the optical element formed by the metasurface, for example, corresponds to the length of the optical element for coupling in or out formed by the metasurface including the lines 1812. In some embodiments, the second line has a length L 2 , and this length L 2 is about 40% to about 60% of the unit cell pitch Λ a , for example, about 50% of Λ a . In some embodiments, L 1 is such that one or more of the first lines 1812 span a distance corresponding to five second lines 1816 in the y - direction. However, it should be understood that according to various embodiments, one or more of the first lines 1812 can span a distance corresponding to any suitable number of second lines 1816 greater than 1 in the y - direction, for example, greater than 10, greater than 20, greater than 50, or greater than 100, or within the range between 10, 20, and 100.

[0196] Still referring to Figure 18A and 18B, in some embodiments, each of the second lines 1816 has the same length such that the second lines 1816 extend in the x - direction and terminate together without crossing any of the one or more first lines 1812. However, embodiments in which the second lines 1816 have different lengths are possible.

[0197] Still referring to Figure 18A the embodiment shown, the extension direction (y - direction) of the one or more first lines 1812 is substantially perpendicular to the extension direction (x - direction) of the second lines 1816. That is, when observing the propagation direction of the incident light (i.e., into the page), the second lines 1816 are rotated by a rotation angle of π / 2 with respect to the one or more first lines 1812. However, the embodiments are not limited thereto, and when observing the propagation direction of the incident light (i.e., into the page), the second lines 1816 can extend in any direction that is rotated by an angle less than π / 2 in the counter - clockwise direction. For example, the second lines 1816 can be rotated with respect to the one or more first lines 1812 in a manner similar to the rotation of the nanobeams of the waveplate shown in Figures 17B - 17H with respect to the waveplate shown in Figure 17A For example, the second lines 1816 can be rotated with respect to the one or more first lines 1812 by rotation angles θ of π / 4, π / 2, 3π / 4, π, 5π / 4, 3π / 2, and 7π / 4. Thus, when an |LCP> beam is incident on the metasurface 1808 having the first and second lines 1812 and 1816, an |RCP> output beam is generated, where the final phase delay of the polarization vectors corresponding to TE and TM polarizations can have a value, where θ is the change in the rotation angle when the fast axis of the waveplate is rotated by the rotation angle θ. In particular, for the embodiment shown, the second lines 1816 rotated by θ = π / 2 with respect to the one or more first lines 1812 diffract the incident beam, e.g., an |LCP> beam, thereby generating a diffracted |RCP> beam, where the diffracted beam is delayed by Thus, in the embodiment shown in the figure, after passing through the metasurface 1808 in which the one or more first lines 1812 and the second lines 1816 are alternately arranged in the x - direction with a constant orientation angle difference Δθ = π / 2, the transmitted RCP wave shows a constant phase difference between adjacent lines among the one or more first lines 1812 and the second lines 1816 As a result, by varying the fast - axis orientation between 0 and π, phase pickup / delay covering the entire 0 - 2π range can be achieved, but compared with the Figures 17A - 17H example shown, the unit - cell pitch is more compact and the diffraction angle is larger.

[0198] Display device having a grating based on a geometric - phase metasurface formed from a polymer - based optical structure incorporating an inorganic material Figure 9A

[0199] As disclosed herein, in the various embodiments described above, a periodic polymer-based optical structure incorporating an inorganic material that can be configured as a metasurface can be implemented as a light-coupling optical element (e.g., as one or more of light-coupling optical elements 700, 710, 720( Figure 6 )) to couple in incident light such that the light propagates through the substrate 1304 via total internal reflection. However, it is recognized that the metasurface 1808 can also be configured to deflect light incident thereon from within the substrate 1804. In some embodiments, the metasurfaces disclosed herein can be applied to form light-coupling optical elements, such as light-coupling optical elements 570, 580, 590, 600, 610( Figure 9B ) or 800, 810, 820( Figure 9B ) in place of or in addition to forming light-coupling optical elements at different locations on the surface 2000a. In some other embodiments, the metasurface 1808 can be used as a light distribution element (e.g., OPE) 730, 740, 750( Figure 19 ). In the case where different waveguides have different associated component colors, it will be understood that the light-coupling optical elements and / or light-coupling optical elements associated with each waveguide can have geometric dimensions and / or periodicities specific to the wavelength or color of the light that the waveguide is configured to propagate. Thus, different waveguides can have metasurfaces with different arrangements of one or more first lines 1812 and second lines 1816. In particular, the different arrangements can depend on the wavelength or color of the incident light beam. For example, depending on the color of the incident light beam, Λ can be configured differently according to the wavelength at which the grating 1800 is configured to diffract a . For example, in order to diffract at least red, green, or blue light, the metasurface 1808 can be configured to have a Λ of less than a wavelength in the range of about 620 - 780 nm, less than a wavelength in the range of about 620 nm, and less than a wavelength in the range of about 435 - 493 nm, respectively a . To scale Λ a , parameters such as the refractive index, width, height, and spacing of one or more of the first lines 1312 and / or second lines 1316 can be adjusted proportionally. Alternatively, as described above, by compensating for one or more of sinα, n 2 and sinθ, Λ a can be kept relatively uniform for different incident light wavelengths.

[0200] Figures 18A - 18B shows a top view of a diffraction grating 2500 including a metasurface having geometric phase optical elements according to some other embodiments. It will be understood that some embodiments of the metasurfaces disclosed herein can be formed by two to four sets of nanobeams, each set of nanobeams extending in a different direction. Figure 19 shows a metasurface having two sets of nanobeamsFigure 19 shows a metasurface having four sets of nanobeams. In particular, Figure 18A the diffraction grating 2500 of Figure 18A and 18B includes a 4-level geometric phase metasurface. Similar to the diffraction grating 1800 referred to above Figure 18A and 18B described, the diffraction grating 2500 includes a substrate, such as a waveguide, on which a metasurface configured to diffract light having a wavelength in the visible spectrum is formed. The metasurface includes one or more first lines 2512 extending in a first lateral direction (e.g., the y-direction) and a plurality of second lines 2516 extending in a second direction (e.g., the x-direction). The one or more first lines 2512 and the second lines 2516 are arranged adjacent to each other in the second direction, wherein the first lines 2512 and the second lines 2516 are alternately repeated in the second direction with a period less than the wavelength of the visible spectrum that the metasurface is configured to diffract. In some embodiments, the second lines 2516 are laterally stacked in the y-direction between adjacent pairs of the first lines 2512. Various features of the one or more first lines 1812 and the second lines 1816 in the diffraction grating 2500 are similar to the corresponding features of the diffraction grating 1800 referred to above Figure 18A and 18B described, except for the following differences.

[0201] Different from the diffraction grating 1800 referred to above Figure 18A and 18B described, the diffraction grating 2500 further includes one or both of a plurality of third lines 2514 extending in a third direction and a plurality of fourth lines 2518 extending in a fourth direction. Each of the first, second, third, and fourth directions may be different from each other. The plurality of third lines 2514 can be regarded as forming a third set of nanobeams, and the plurality of fourth lines 2518 can be regarded as forming a fourth set of nanobeams. The third lines 2514 are disposed on a first side of the second lines 2516 and are inserted between the one or more first lines 2512 and the second lines 2516 in the second direction (e.g., the x-axis direction). The fourth lines 2518 are disposed on a second side of the second lines 2516 opposite to the first side and are inserted between another one or more first lines 2512 and the second lines 2516 in the second direction (e.g., the x-direction).

[0202] Different from the diffraction grating 1800 referred to above Figure 18A and 18B described, the diffraction grating 2500 may have only one first line 2512. In some other embodiments, the diffraction grating 2500 may have a plurality of first lines 2512, e.g., a pair of first lines, such as the diffraction grating 1800 referred to above Figures 17A - 17H and 18B described.

[0203] In some embodiments, the third lines 2514 have the same length and / or the fourth lines 2518 have the same length such that the third lines 2514 and / or the fourth lines 2518 terminate together in the third direction and the fourth direction, respectively. However, other embodiments are possible where different ones of the third lines 2514 and / or different ones of the fourth lines 2518 do not terminate together. Additionally, in some embodiments, the third lines 2514 that terminate together and the fourth lines 2518 that terminate together have the same length. However, in other embodiments, the third lines 2514 that terminate together and the fourth lines 2518 that terminate together have different lengths.

[0204] In some embodiments, adjacent ones of the third lines 2514 are spaced apart by a constant interval in a first direction (e.g., the y direction) and / or adjacent ones of the fourth lines 2518 are spaced apart by a constant interval in a first direction (e.g., the y direction). However, other embodiments are possible where the third lines 2514 and / or the fourth lines 2518 are not spaced apart by a constant interval. Additionally, in some embodiments, the third lines 2514 spaced apart by a constant interval and the fourth lines 2518 spaced apart by a constant interval have the same constant interval. However, in other embodiments, the third lines 2514 spaced apart by a constant interval and the fourth lines 2518 spaced apart by a constant interval have different intervals.

[0205] In some embodiments, the third lines 2514 have the same width and / or the fourth lines 2518 have the same width. However, in other embodiments, the third lines 2514 and / or the fourth lines 2518 have different widths. Additionally, in some embodiments, the width of the third lines 2514 having the same width and the width of the fourth lines 2518 having the same width are the same. However, in some other embodiments, the width of the third lines 2514 having the same width and the width of the fourth lines 2518 having the same width are different. Additionally, in some embodiments, the third lines 2514 and the fourth lines 2518 have the same width as one or both of the first lines 2512 and the second lines 2416.

[0206] In some embodiments, when observing the propagation direction of incident light (e.g., entering the page), the third line 2514 extends in a third direction that rotates counterclockwise by an angle relative to one or more first lines 2512, and this angle is less than the minimum rotation angle of the second line 2516 relative to one or more first lines 2512. In some embodiments, the second line 2516 rotates 90° or π / 2 relative to one or more first lines 2512, and the third line 2514 rotates 45° or π / 4 relative to one or more first lines 2512. Additionally, when observing the propagation direction of incident light, the fourth line 2518 extends in a fourth direction that rotates counterclockwise by an angle relative to one or more first lines 2512, and this angle is greater than the minimum rotation angle of the second line 2516 relative to one or more first lines 2512. In some embodiments, the second line 2516 rotates 90° or π / 2 relative to one or more first lines 2512, and the third line 2514 rotates 135° or 3π / 4 relative to one or more first lines 2512.

[0207] In some embodiments, similar to the combination of wave plates shown above with reference to Figure 12A - 1 the phase difference caused by the relative orientation of one or more first lines 2512, second line 2516, third line 2514, and fourth line 2518 can vary between 0 and π. According to some embodiments, when the third line 2514, fourth line 2518, and second line 2516 rotate π / 4, 3π / 4, and π relative to one or more first lines 2512 respectively, phase pick-up / delay of π / 2, 3π / 2, and 2π can be achieved respectively, so that phase pick-up / delay covering the entire 0 - 2π range can be realized. As a result, by varying the fast axis orientation between 0 and π, phase pick-up / delay covering the entire 0 - 2π range can be achieved, but compared with Display device based on a geometric - phase metasurface, the metasurface comprising a polymer - based optical structure incorporating an inorganic material the example shown in 2H, it has a more compact unit cell pitch and a higher diffraction angle.

[0208] optical structure Figure 9A

[0209] In various embodiments of the display system (e.g., with reference to Figure 18A and 9B ), a set of waveguides 1200 may include a periodic polymer-based optical structure incorporating an inorganic material, which can be configured as a metasurface diffraction grating operating in a transmission mode. In various embodiments, the waveguide group 1200 includes waveguides 670, 680, 690 corresponding to each component color (R, G, B), and in turn, a corresponding one of the optical coupling elements 700, 710, 720 is formed therein or thereon, which may include or correspond to the above reference Figure 18A 、 18BThe diffraction gratings 1300, 2500 described in and 19. The waveguides 670, 680, 690 also form corresponding ones of the light distribution elements (e.g., OPE) 730, 740, 750 and / or the light extraction optical elements (e.g., EPE) 800, 810, 820 therein or thereon, which include or correspond to the EPE / OPE 1846 referred to above Figure 9A and 18B described. In operation, in some embodiments, when an incident light beam 1830, such as visible light, is incident on the metasurface 1808 at an incident angle α, the gratings 1800, 2500 diffract the incident light into diffracted light beams 1842, 1838 at a diffraction angle θ 2 When total internal reflection occurs for the substrate 1804 of the waveguide configured to have a refractive index n 2 such that one or both of the diffracted light beams 1838 and 1842 are diffracted at a diffraction angle exceeding the critical angle θ TIR i.e., when the condition θ 2 > θ TIR and θ 1 > θ TIR is satisfied for one or both of them, one or both of the diffracted light beams 1838 and 1842 propagate along the x-axis in their respective opposite directions by total internal reflection (TIR). Subsequently, in some embodiments, the diffracted light beam 1846 is coupled into the substrate 1804 in the TIR mode until it reaches the orthogonal pupil expander (OPE) 1846 or the exit pupil expander (EPE) 1846, as referred to above in Figure 6 and 9B described.

[0210] It will be understood that the substrate 1804 configured as a waveguide having a metasurface formed thereon according to various embodiments can be used to form a display system, such as the system 250 disclosed herein ( Figure 6 ). For example, the metasurface can be used as the light coupling, light distribution, and / or light extraction optical elements described herein. In some embodiments, after manufacturing the metasurface, the waveguide 2000 can be optically coupled to a light pipe, such as a light pipe for injecting image information from a spatial light modulator into the waveguide. In some embodiments, the light pipe can be an optical fiber. Examples of light pipes include the image injection devices 360, 370, 380, 390, 400 ( Other examples ) and scanning optical fibers. In some embodiments, a plurality of waveguides each having a metasurface 1808 can be provided, and each of these waveguides can be optically coupled to one or more image injection devices.

[0211] ​

[0212] 1. A method of manufacturing an optical element, comprising:

[0213] Provide a substrate having a first refractive index and being transparent in the visible spectrum;

[0214] Form a periodically repeating polymer structure on the substrate; and

[0215] Expose the substrate to a metal precursor and then to an oxidizing precursor,

[0216] wherein the exposure is performed at a pressure and temperature such that an inorganic material of a metal including the metal precursor is incorporated into the periodically repeating polymer structure, thereby forming a pattern of a periodically repeating optical structure configured to diffract visible light, the optical structure having a second refractive index greater than the first refractive index.

[0217] 2. The method according to Example 1, wherein the exposure is performed at a pressure between about 100 mTorr and about 10 Torr.

[0218] 3. The method according to Example 1 or Example 2, wherein the exposure is performed at a temperature below about 150 degrees Celsius.

[0219] 4. The method according to any one of the foregoing examples, wherein forming the periodically repeating polymer structure includes patterning by nanoimprinting.

[0220] 5. The method according to any one of the foregoing examples, wherein forming the periodically repeating polymer structure includes photolithographic patterning.

[0221] 6. The method according to any one of the foregoing examples, wherein the periodically repeating polymer structure is formed of a material having a bulk refractive index less than the second refractive index, and the inorganic material has a bulk refractive index greater than the second refractive index.

[0222] 7. The method according to any one of the foregoing examples, wherein the second refractive index is greater than 1.7 and is at least 0.2 greater than the first refractive index.

[0223] 8. The method according to any one of the foregoing examples, wherein the substrate has a refractive index greater than 1.5.

[0224] 9. The method according to any one of the foregoing examples, wherein the periodically repeating polymer structure includes a photoresist.

[0225] 10. The method according to any one of the foregoing examples, wherein exposing the substrate to the metal precursor includes: exposing to a precursor including a transition metal selected from the group consisting of aluminum, zinc, zirconium, hafnium, and titanium.

[0226] 11. The method according to any one of the foregoing examples, wherein exposing the substrate to the metal precursor and the oxidation precursor comprises: exposing at a partial pressure of the respective precursor for a duration sufficient to fill the exposed surface of the periodically repeating polymer structure with at least a monolayer of inorganic material.

[0227] 12. The method according to any one of the foregoing examples, wherein exposing the substrate to one or both of the metal precursor and the oxidation precursor comprises: exposing for a duration of more than 1 second.

[0228] 13. The method according to any one of the foregoing examples, wherein the inorganic material incorporated into the periodically repeating polymer structure comprises a metal oxide.

[0229] 14. The method according to example 13, wherein the metal oxide comprises a transition metal oxide.

[0230] 15. The method according to example 14, wherein the metal oxide comprises an oxide selected from the group consisting of: alumina, zinc oxide, zirconia, hafnia, and titanium oxide.

[0231] 16. The method according to any one of the foregoing examples, wherein the exposure to incorporate the inorganic material is selectively through the exposed surface of the periodically repeating polymer structure relative to the exposed surface of the substrate.

[0232] 17. The method according to example 16, wherein forming the periodically repeating polymer structure comprises spacing apart, the space having a substrate surface on which no polymer layer is provided, wherein the exposure does not result in deposition of the inorganic material on the substrate surface in the space or does not result in incorporation of the inorganic material through the substrate surface in the space.

[0233] 18. The method according to example 16, wherein forming the periodically repeating polymer structure comprises spacing apart, the space having a substrate surface on which a polymer layer is provided, the polymer layer having a thickness less than the height of the periodically repeating polymer structure, wherein the exposure incorporates the inorganic material into the polymer layer formed on the substrate surface in the space.

[0234] 19. The method according to example 18, wherein the entire thickness of the polymer layer formed on the substrate surface in the space is incorporated with the inorganic material.

[0235] 20. The method according to Example 18, wherein the polymer layer formed on the substrate surface in the space has a partial thickness bonded to the inorganic material and a partial thickness not bonded to the inorganic material.

[0236] 21. An optical element, comprising:

[0237] a substrate having a first refractive index and being transparent in the visible spectrum; and

[0238] a pattern of periodically repeating optical structures formed on the substrate and configured to diffract visible light, the optical structures having a second refractive index greater than the first refractive index and comprising a polymer material in which an inorganic material is incorporated.

[0239] 22. The optical element according to Example 21, wherein the polymer material has a bulk refractive index less than the second refractive index, and the inorganic material has a bulk refractive index higher than the second refractive index.

[0240] 23. The optical element according to Example 21 or Example 22, wherein the second refractive index is greater than 1.7 and is at least 0.2 greater than the first refractive index.

[0241] 24. The optical element according to any one of Examples 21 to 23, wherein the substrate has a refractive index greater than 1.5.

[0242] 25. The optical element according to any one of Examples 21-24, wherein the polymer material comprises a photoresist.

[0243] 26. The optical element according to any one of Examples 21-25, wherein the inorganic material comprises a transition metal oxide.

[0244] 27. The optical element according to Example 26, wherein the inorganic material comprises a metal oxide.

[0245] 28. The optical element according to Example 27, wherein the metal oxide comprises an oxide selected from the group consisting of: aluminum oxide, zinc oxide, zirconium oxide, hafnium oxide, and titanium oxide.

[0246] 29. The optical element according to Example 27, wherein the inorganic material is incorporated into the surface region of the optical structure, and the core region of the optical structure does not have an inorganic material incorporated therein.

[0247] 30. The optical element according to any one of Examples 21 - 29, wherein adjacent optical structures in the periodically repeating optical structure are spaced apart spatially, and wherein the surface of the substrate in the space does not have the inorganic material disposed thereon.

[0248] 31. The optical element according to any one of Examples 21 to 30, wherein adjacent optical structures in the periodically repeating optical structure are spaced apart spatially, and wherein a polymer material layer in which the inorganic material is incorporated is formed on the surface of the substrate in the space, and the layer has a thickness less than the height of the optical structure.

[0249] 32. The optical element according to Example 31, wherein the entire thickness of the polymer material layer formed in the space is combined with the inorganic material.

[0250] 33. The optical element according to Example 31, wherein a part of the thickness of the polymer material layer formed in the space is combined with the inorganic material in the surface region and a part of the thickness is not combined with the inorganic material.

[0251] 34. The optical element according to any one of Examples 21 - 33, wherein the substrate is configured such that visible light diffracted by the periodically repeating optical structure propagates under total internal reflection.

[0252] 35. An optical system, comprising:

[0253] An optical element, comprising:

[0254] A substrate having a first refractive index and being transparent in the visible spectrum, and

[0255] A pattern of periodically repeating optical structures formed on the substrate and configured to diffract visible light, the optical structures having a second refractive index greater than the first refractive index and comprising a polymer material in which an inorganic material is incorporated,

[0256] wherein the periodically repeating optical structure includes nanobeams arranged as a metasurface, the metasurface including a plurality of repeating unit cells, each unit cell including:

[0257] A first group of nanobeams formed by one or more first nanobeams; and

[0258] A second group of nanobeams formed by one or more second nanobeams, the one or more second nanobeams being adjacent to the one or more first nanobeams and spaced apart from each other by a sub - wavelength interval,

[0259] Among them, the one or more first nanobeams and the plurality of second nanobeams elongate in different orientation directions.

[0260] 36. The optical system according to Example 35, wherein the unit cell repeats with a period of less than or equal to about 10 nm to 1 μm.

[0261] 37. The optical system according to Example 35 or Example 36, wherein the one or more first nanobeams and the second nanobeams are oriented at an angle with respect to each other to cause a phase difference between the visible light diffracted by the one or more first nanobeams and the visible light diffracted by the second nanobeams.

[0262] 38. The optical system according to any one of Examples 35 - 37, wherein the one or more first nanobeams and the second nanobeams are oriented in orientation directions that are rotated about 90 degrees with respect to each other.

[0263] 39. The optical system according to any one of Examples 35 - 38, wherein the unit cell repeats with a period less than or equal to the wavelength, where the wavelength is within the visible spectrum.

[0264] 40. The optical system according to any one of Examples 35 - 39, wherein the one or more first nanobeams and the second nanobeams have a height less than the wavelength.

[0265] 41. An optical system, comprising a waveguide configured to propagate visible light, the optical system comprising:

[0266] A substrate having a first refractive index and being transparent in the visible spectrum so that light can be guided therein by total internal reflection; and

[0267] A pattern of periodically repeating optical structures formed on the substrate and configured to diffract visible light, the optical structures having a second refractive index greater than the first refractive index and comprising a polymer material in which an inorganic material is incorporated,

[0268] Wherein the periodically repeating optical structures are arranged to diffract light at a diffraction angle with respect to the direction of incident light and cause the diffracted light to propagate in the substrate under total internal reflection, or are arranged to diffract the light guided in the substrate under total internal reflection at a diffraction angle with respect to the direction of the light guided in the substrate.

[0269] 42. The optical system according to Example 41, wherein the polymer material has a bulk refractive index less than the second refractive index, and the inorganic material has a bulk refractive index higher than the second refractive index.

[0270] 43. The optical system according to Example 41 or Example 42, wherein the second refractive index is greater than 1.7 and is at least 0.2 greater than the first refractive index.

[0271] 44. The optical system according to any one of Examples 41 - 43, wherein the diffraction angle exceeds 50 degrees.

[0272] 45. The optical system according to any one of Examples 41 - 44, further comprising a light source configured to emit light of the wavelength onto the pattern of the periodically repeating optical structure.

[0273] 46. The optical system according to any one of Examples 41 to 45, further comprising a spatial light modulator configured to modulate light from the light source and output the modulated light onto the pattern of the periodically repeating optical structure.

[0274] 47. A head - mounted display device configured to project light onto a user's eyes to display augmented reality image content, the head - mounted display device comprising:

[0275] A frame configured to be supported on the user's head;

[0276] A display disposed on the frame, at least a portion of the display comprising:

[0277] One or more waveguides that are transparent and are disposed in a position in front of the user's eyes when the user wears the head - mounted display device, such that the transparent portion transmits light from a portion of the environment in front of the user to the user's eyes to provide a view of that portion of the environment in front of the user;

[0278] One or more light sources; and

[0279] At least one diffraction grating configured to couple light from the light source into the one or more waveguides or out of the one or more waveguides, the diffraction grating comprising an optical element, the optical element comprising:

[0280] A substrate having a first refractive index and being transparent in the visible spectrum; and

[0281] A pattern of periodically repeating optical structures formed on the substrate and configured to diffract visible light, the optical structures having a second refractive index greater than the first refractive index and comprising a polymer material in which an inorganic material is incorporated.

[0282] 48. The apparatus according to Example 47, wherein the one or more light sources include a fiber optic scanning projector.

[0283] 49. The apparatus according to Example 47 or Example 48, wherein the display is configured to project light into the user's eyes to present image content to the user on a plurality of depth planes.

[0284] 50. The method according to any one of Examples 1 - 20, wherein the exposure is performed at a pressure less than 10 atm (atmospheric pressure).

[0285] 51. The method according to any one of Examples 1 - 20 and 50, wherein the exposure is performed at a temperature greater than 25 degrees Celsius.

[0286] 52. The method according to any one of Examples 1 - 20 and 50 - 51, wherein exposing the substrate to one or both of the metal precursor and the oxidation precursor includes: exposing for a duration of about 1 second to about 1000 seconds.

[0287] 53. The method according to any one of Examples 1 - 20 and 50 - 52, wherein the inorganic material incorporated into the periodically repeating polymer structure includes metal nitride.

[0288] 54. The optical element according to any one of Examples 21 - 34, wherein the periodically repeating optical structure includes a metasurface.

[0289] 55. The optical element according to any one of Examples 21 - 34 and 54, wherein the substrate is configured such that visible light is guided therein by total internal reflection and diffracted out of the substrate by the periodically repeating optical structure.

[0290] 56. The optical element according to any one of Examples 21 - 34 and 54 - 55, wherein the substrate is configured such that visible light is guided therein by total internal reflection and diffracted by the periodically repeating optical structure so as to change the direction of propagation of the light beam in the substrate by total internal reflection.

[0291] 57. The optical system according to any one of Examples 41 - 46, wherein the periodically repeating optical structure is arranged to diffract light at a diffraction angle with respect to the direction of the incident light and cause the diffracted light to propagate in the substrate by total internal reflection.

[0292] 58. The optical system according to any one of Examples 41 - 46 and 57, wherein the periodically repeating optical structure is arranged to diffract the light guided in the substrate by total internal reflection at a diffraction angle with respect to the direction of the light guided in the substrate.

[0293] 59. The optical system according to Example 58, wherein the periodically repeating optical structure is arranged to diffract light guided by total internal reflection within the substrate out of the substrate.

[0294] 60. A method of manufacturing an optical element, comprising:

[0295] providing a substrate that is transparent in the visible spectrum;

[0296] forming a periodically repeating polymer structure having a first refractive index on the substrate; and

[0297] exposing the substrate to a metal precursor and then to an oxidation precursor,

[0298] wherein the exposure is performed at a pressure and temperature such that an inorganic material of a metal including the metal precursor is incorporated into the periodically repeating polymer structure, thereby increasing the refractive index of the periodically repeating polymer structure to form a pattern of a periodically repeating optical structure configured to diffract visible light.

[0299] 61. The method according to Example 60, wherein the exposure is performed at a pressure between about 100 mTorr and about 10 Torr.

[0300] 62. The method according to Example 60 or Example 61, wherein the exposure is performed at a temperature below about 150 degrees Celsius.

[0301] 63. The method according to any one of Examples 60 - 62, wherein forming the periodically repeating polymer structure includes patterning by nanoimprinting.

[0302] 64. The method according to any one of Examples 60 - 63, wherein forming the periodically repeating polymer structure includes photolithographic patterning.

[0303] 65. The method according to any one of Examples 60 - 64, wherein the periodically repeating polymer structure is formed of a material having a bulk refractive index less than that of the periodically repeating optical structure, and the inorganic material has a bulk refractive index greater than that of the periodically repeating optical structure.

[0304] 66. The method according to any one of Examples 60 - 65, wherein the refractive index of the periodically repeating optical structure is greater than 1.7 and is at least 0.2 greater than the refractive index of the periodically repeating polymer structure.

[0305] 67. The method according to any one of Examples 60 - 66, wherein the substrate has a refractive index greater than 1.5.

[0306] 68. A method according to any one of Examples 60 - 67, wherein the periodically repeating polymer structure comprises a photoresist.

[0307] 69. A method according to any one of Examples 60 - 68, wherein exposing the substrate to the metal precursor comprises: exposing to a precursor comprising a transition metal selected from the group consisting of aluminum, zinc, zirconium, hafnium, and titanium.

[0308] 70. A method according to any one of Examples 60 - 69, wherein exposing the substrate to the metal precursor and the oxidation precursor comprises: exposing at a partial pressure of the respective precursor and for a duration sufficient to fill the exposed surface of the periodically repeating polymer structure with at least a monolayer of inorganic material.

[0309] 71. A method according to any one of Examples 60 - 70, wherein exposing the substrate to one or both of the metal precursor and the oxidation precursor comprises: exposing for a duration of more than 1 second.

[0310] 72. A method according to any one of Examples 60 - 71, wherein the inorganic material incorporated into the periodically repeating polymer structure comprises a metal oxide.

[0311] 73. A method according to Example 72, wherein the metal oxide comprises a transition metal oxide.

[0312] 74. A method according to Example 73, wherein the metal oxide comprises an oxide selected from the group consisting of aluminum oxide, zinc oxide, zirconium oxide, hafnium oxide, and titanium oxide.

[0313] 75. A method according to any one of Examples 60 - 74, wherein the exposure to incorporate the inorganic material is selectively through the exposed surface of the periodically repeating polymer structure relative to the exposed surface of the substrate.

[0314] 76. A method according to Example 75, wherein forming the periodically repeating polymer structure comprises spacing apart, the space having a substrate surface on which no polymer layer is provided, wherein exposure does not result in deposition of the inorganic material on the substrate surface in the space or does not result in incorporation of the inorganic material through the substrate surface in the space.

[0315] 77. The method according to Example 75, wherein forming the periodically repeating polymer structure includes spacing apart, with a substrate surface having a polymer layer disposed thereon, the polymer layer having a thickness less than the height of the periodically repeating polymer structure, wherein exposure binds the inorganic material into the polymer layer formed on the substrate surface within the space.

[0316] 78. The method according to Example 77, wherein the entire thickness of the polymer layer formed on the substrate surface within the space is bound to the inorganic material.

[0317] 79. The method according to Example 77, wherein the polymer layer formed on the substrate surface within the space has a portion of its thickness bound to the inorganic material and a portion of its thickness not bound to the inorganic material.

[0318] 80. A method of manufacturing an optical element, comprising:

[0319] providing a substrate having a first refractive index and being transparent in the visible spectrum, wherein the substrate has a periodically repeating polymer structure formed thereon; and

[0320] exposing the substrate to a metal precursor and then to an oxidation precursor,

[0321] wherein the exposure is performed at a pressure and temperature such that an inorganic material of a metal including the metal precursor is bound into the periodically repeating polymer structure, thereby forming a pattern of a periodically repeating optical structure configured to diffract visible light, the optical structure having a second refractive index greater than the first refractive index.

[0322] 81. The method according to Example 80, wherein the exposure is performed at a pressure between about 100 mTorr and about 10 Torr.

[0323] 82. The method according to Example 80 or Example 81, wherein the exposure is performed at a temperature below about 150 degrees Celsius.

[0324] 83. The method according to any one of Examples 80 - 82, wherein forming the periodically repeating polymer structure includes patterning by nanoimprinting.

[0325] 84. The method according to any one of Examples 80 - 83, wherein forming the periodically repeating polymer structure includes photolithographic patterning.

[0326] 85. The method according to any one of Examples 80 - 84, wherein the periodically repeating polymer structure is formed of a material having a bulk refractive index less than the second refractive index, and the inorganic material has a bulk refractive index greater than the second refractive index.

[0327] 86. The method according to any one of Examples 80 - 85, wherein the second refractive index is greater than 1.7 and is at least 0.2 greater than the first refractive index.

[0328] 87. The method according to any one of Examples 80 - 86, wherein the substrate has a refractive index greater than 1.5.

[0329] 88. The method according to any one of Examples 80 - 87, wherein the periodically repeating polymer structure comprises a photoresist.

[0330] 89. The method according to any one of Examples 80 - 88, wherein exposing the substrate to the metal precursor comprises: exposing to a precursor comprising a transition metal selected from the group consisting of aluminum, zinc, zirconium, hafnium, and titanium.

[0331] 90. The method according to any one of Examples 80 - 89, wherein exposing the substrate to the metal precursor and the oxidation precursor comprises: exposing at the partial pressure of the respective precursor for a duration sufficient to fill the exposed surface of the periodically repeating polymer structure with at least a monolayer of the inorganic material.

[0332] 91. The method according to any one of Examples 80 - 90, wherein exposing the substrate to one or both of the metal precursor and the oxidation precursor comprises: exposing for a duration exceeding 1 second.

[0333] 92. The method according to any one of Examples 80 - 91, wherein the inorganic material incorporated into the periodically repeating polymer structure comprises a metal oxide.

[0334] 93. The method according to Example 92, wherein the metal oxide comprises a transition metal oxide.

[0335] 94. The method according to Example 93, wherein the metal oxide comprises an oxide selected from the group consisting of aluminum oxide, zinc oxide, zirconium oxide, hafnium oxide, and titanium oxide.

[0336] 95. The method according to any one of Examples 80 - 94, wherein the exposure to incorporate the inorganic material is selectively through the exposed surface of the periodically repeating polymer structure relative to the exposed surface of the substrate.

[0337] 96. The method according to Example 95, wherein forming the periodically repeating polymer structure includes separating by spaces having a substrate surface on which no polymer layer is provided, wherein exposing does not cause deposition of the inorganic material on the substrate surface in the spaces or does not cause bonding of the inorganic material through the substrate surface in the spaces.

[0338] 97. The method according to Example 96, wherein forming the periodically repeating polymer structure includes separating by spaces having a substrate surface on which a polymer layer is provided, the polymer layer having a thickness less than the height of the periodically repeating polymer structure, wherein exposing bonds the inorganic material into the polymer layer formed on the substrate surface in the spaces.

[0339] 98. The method according to Example 97, wherein the entire thickness of the polymer layer formed on the substrate surface in the spaces bonds with the inorganic material.

[0340] 99. The method according to Example 97, wherein the polymer layer formed on the substrate surface in the spaces has a partial thickness that bonds with the inorganic material and a partial thickness that does not bond with the inorganic material.

[0341] 100. The method according to any one of Examples 80 - 99, wherein exposing is performed at a pressure of less than 10 atm (atmospheric pressure).

[0342] 101. The method according to any one of Examples 80 - 100, wherein exposing is performed at a temperature greater than 25 degrees Celsius.

[0343] 102. The method according to any one of Examples 80 - 101, wherein exposing the substrate to one or both of the metal precursor and the oxidation precursor includes: exposing for a duration of about 1 second to about 1000 seconds.

[0344] 103. The method according to any one of Examples 80 - 102, wherein the inorganic material incorporated into the periodically repeating polymer structure includes metal nitride.

[0345] 104. The method according to Example 1, wherein exposing is performed at a pressure between about 100 mTorr and about 10 Torr.

[0346] 105. The method according to Example 2, wherein exposing is performed at a temperature below about 150 degrees Celsius.

[0347] 106. The method according to Example 1, wherein forming the periodically repeating polymer structure includes patterning by nanoimprinting.

[0348] 107. The method according to Example 1, wherein forming the periodically repeating polymer structure comprises photolithographic patterning.

[0349] 108. The method according to Example 1, wherein the periodically repeating polymer structure is formed of a material having a bulk refractive index less than the second refractive index, and the inorganic material has a bulk refractive index greater than the second refractive index.

[0350] 109. The method according to Example 1, wherein the second refractive index is greater than 1.7 and is at least 0.2 greater than the first refractive index.

[0351] 110. The method according to Example 1, wherein the substrate has a refractive index greater than 1.5.

[0352] 111. The method according to Example 1, wherein the periodically repeating polymer structure comprises a photoresist.

[0353] 112. The method according to Example 1, wherein exposing the substrate to the metal precursor comprises: exposing to a precursor comprising a transition metal selected from the group consisting of aluminum, zinc, zirconium, hafnium, and titanium.

[0354] 113. The method according to Example 1, wherein exposing the substrate to the metal precursor and the oxidation precursor comprises: exposing at the partial pressure of the respective precursor for a duration sufficient to fill the exposed surface of the periodically repeating polymer structure with at least a monolayer of the inorganic material.

[0355] 114. The method according to Example 1, wherein exposing the substrate to one or both of the metal precursor and the oxidation precursor comprises: exposing for a duration of more than 1 second.

[0356] 115. The method according to Example 1, wherein the inorganic material incorporated into the periodically repeating polymer structure comprises a metal oxide.

[0357] 116. The method according to Example 13, wherein the metal oxide comprises a transition metal oxide.

[0358] 117. The method according to Example 14, wherein the metal oxide comprises an oxide selected from the group consisting of: aluminum oxide, zinc oxide, zirconium oxide, hafnium oxide, and titanium oxide.

[0359] 118. The method according to Example 1, wherein the inorganic material is selectively bound to the exposed surface of the substrate through the exposed surface of the periodically repeating polymer structure.

[0360] 119. The method according to Example 16, wherein forming the periodically repeating polymer structure includes spacing by a space having a substrate surface on which no polymer layer is provided, wherein exposing does not cause the inorganic material to deposit on the substrate surface in the space or does not cause the inorganic material to bond through the substrate surface in the space.

[0361] 120. The method according to Example 16, wherein forming the periodically repeating polymer structure includes spacing by a space having a substrate surface on which a polymer layer is provided, the polymer layer having a thickness less than the height of the periodically repeating polymer structure, wherein exposing bonds the inorganic material into the polymer layer formed on the substrate surface in the space.

[0362] 121. The method according to Example 18, wherein the entire thickness of the polymer layer formed on the substrate surface in the space bonds with the inorganic material.

[0363] 122. The method according to Example 18, wherein the polymer layer formed on the substrate surface in the space has a partial thickness that bonds with the inorganic material and a partial thickness that does not bond with the inorganic material.

[0364] 123. The method according to Example 80, wherein exposing is performed at a pressure between about 100 mTorr and about 10 Torr.

[0365] 124. The method according to Example 80, wherein exposing is performed at a temperature below about 150 degrees Celsius.

[0366] 125. The method according to Example 80, wherein forming the periodically repeating polymer structure includes patterning by nanoimprinting.

[0367] 126. The method according to Example 80, wherein forming the periodically repeating polymer structure includes photolithographic patterning.

[0368] 127. The method according to Example 80, wherein the periodically repeating polymer structure is formed of a material having a bulk refractive index less than the refractive index of the periodically repeating optical structure, and the inorganic material has a bulk refractive index greater than the refractive index of the periodically repeating optical structure.

[0369] 128. The method according to Example 80, wherein the refractive index of the periodically repeating optical structure is greater than 1.7 and is at least 0.2 greater than the refractive index of the periodically repeating polymer structure.

[0370] 129. The method according to Example 80, wherein the substrate has a refractive index greater than 1.5.

[0371] 130. The method according to Example 80, wherein the periodically repeating polymer structure comprises a photoresist.

[0372] 131. The method according to Example 80, wherein exposing the substrate to the metal precursor comprises: exposing to a precursor comprising a transition metal selected from the group consisting of aluminum, zinc, zirconium, hafnium, and titanium.

[0373] 132. The method according to Example 80, wherein exposing the substrate to the metal precursor and the oxidation precursor comprises: exposing at the partial pressure of the respective precursor and for a duration sufficient to fill the exposed surface of the periodically repeating polymer structure with at least a monolayer of inorganic material.

[0374] 133. The method according to Example 80, wherein exposing the substrate to one or both of the metal precursor and the oxidation precursor comprises: exposing for a duration of more than 1 second.

[0375] 134. The method according to Example 80, wherein the inorganic material incorporated into the periodically repeating polymer structure comprises a metal oxide.

[0376] 135. The method according to Example 134, wherein the metal oxide comprises a transition metal oxide.

[0377] 136. The method according to Example 135, wherein the metal oxide comprises an oxide selected from the group consisting of aluminum oxide, zinc oxide, zirconium oxide, hafnium oxide, and titanium oxide.

[0378] 137. The method according to Example 80, wherein the incorporation of the inorganic material by exposure is selectively relative to the exposed surface of the substrate through the exposed surface of the periodically repeating polymer structure.

[0379] 138. The method according to Example 137, wherein forming the periodically repeating polymer structure comprises spacing by a space having a substrate surface on which no polymer layer is provided, wherein exposure does not cause deposition of the inorganic material on the substrate surface in the space or does not cause incorporation of the inorganic material through the substrate surface in the space.

[0380] 139. The method according to Example 137, wherein forming the periodically repeating polymer structure includes being spaced apart by a space having a substrate surface on which a polymer layer is disposed, the polymer layer having a thickness less than the height of the periodically repeating polymer structure, wherein exposing binds the inorganic material into the polymer layer formed on the substrate surface in the space.

[0381] 140. The method according to Example 139, wherein the entire thickness of the polymer layer formed on the substrate surface in the space is bound to the inorganic material.

[0382] 141. The method according to Example 139, wherein a portion of the thickness of the polymer layer formed on the substrate surface in the space is bound to the inorganic material and a portion of the thickness is not bound to the inorganic material.

[0383] 142. The method of manufacturing an optical element according to any one of Examples 1-20 and 50-53, wherein the method further includes integrating the optical element as part of a head-mounted augmented reality glasses.

[0384] 143. The method of manufacturing an optical element according to any one of Examples 60-79, wherein the method further includes integrating the optical element as part of a head-mounted augmented reality glasses.

[0385] 144. The method of manufacturing an optical element according to any one of Examples 80-103, wherein the method further includes integrating the optical element as part of a head-mounted augmented reality glasses.

[0386] 145. A head-mounted display device configured to project light onto a user's eyes to display augmented reality image content, the head-mounted display device comprising:

[0387] A frame configured to be supported on a user's head;

[0388] A display disposed on the frame, at least a portion of the display comprising:

[0389] One or more waveguides, the one or more waveguides being transparent and being disposed in a position in front of the user's eyes when the user wears the head-mounted display device, so that the transparent portion transmits light from a portion of the environment in front of the user to the user's eyes to provide a view of that portion of the environment in front of the user;

[0390] One or more light sources; and

[0391] An optical element according to any one of Examples 21 - 34 and 54 - 56, wherein the one or more waveguides of the display include the substrate of the optical element, and wherein the optical element is configured to couple light from the one or more light sources into the one or more waveguides or to couple out light from the one or more waveguides.

[0392] 146. A head - mounted display device configured to project light into a user's eyes to display augmented reality image content, the head - mounted display device comprising:

[0393] A frame configured to be supported on a user's head;

[0394] A display disposed on the frame,

[0395] One or more light sources; and

[0396] An optical element according to any one of Examples 21 - 34 and 54 - 56, wherein the optical element is configured to direct light from the one or more light sources into the user's eyes.

[0397] 147. A head - mounted display device configured to project light into a user's eyes to display augmented reality image content, the head - mounted display device comprising:

[0398] A frame configured to be supported on a user's head;

[0399] A display disposed on the frame,

[0400] One or more light sources; and

[0401] An optical element according to any one of Examples 35 - 40, wherein the optical element is configured to direct light from the one or more light sources into the user's eyes.

[0402] 148. A head - mounted display device configured to project light into a user's eyes to display augmented reality image content, the head - mounted display device comprising:

[0403] A frame configured to be supported on a user's head;

[0404] A display disposed on the frame,

[0405] One or more light sources; and

[0406] An optical element according to any one of Examples 41 - 46 and 57 - 59, wherein the optical element is configured to direct light from the one or more light sources into the user's eyes.

[0407] Various exemplary examples of the present invention are described herein. These examples are referenced in a non-limiting sense. These examples are provided to illustrate broader aspects of the application of the present invention. Various changes may be made to the described invention and equivalents may be substituted without departing from the true spirit and scope of the present invention.

[0408] For example, although advantageously used with an AR display that provides images on multiple depth planes, the augmented reality content disclosed herein may also be displayed by a system that provides images on a single depth plane and / or with a virtual reality display. In some embodiments in which multiplexed image information (e.g., light of different colors) is directed into a waveguide, multiple optical elements or metasurfaces may be provided on the waveguide. For example, for each color of light, one optical element or metasurface is active. In some embodiments, the pitch or period and / or geometric dimensions of the protrusions forming the optical element or metasurface may vary across its entire surface. Such an optical element or metasurface may function in redirecting light of different wavelengths, depending on the geometry and pitch at the location where the light is incident on the optical element or metasurface. In some other embodiments, the geometry and pitch of the optical element or metasurface features are configured to vary such that even deflected light rays having similar wavelengths propagate away from the optical element or metasurface at different angles. It should also be understood that multiple separate optical elements or metasurfaces may be provided across the substrate surface. In some embodiments, each of the optical elements or metasurfaces has the same geometry and pitch, or in some other embodiments, at least some of the optical elements or metasurfaces have different geometry and pitch from other optical elements or metasurfaces.

[0409] Moreover, although advantageously applied to a display such as a wearable display, the optical element or metasurface may be applied to various other devices that require a compact, low-profile light redirecting element. For example, the optical element or metasurface may generally be applied to form light redirecting components of an optical plate (e.g., a glass plate), an optical fiber, a microscope, a sensor, a watch, a camera, and an image projection device.

[0410] In addition, many modifications may be made to adapt a particular situation, material, composition of matter, process, one or more process acts, or one or more steps to the one or more purposes, spirit, or scope of the present invention. Moreover, as will be understood by those skilled in the art, each of the various variations described and shown herein has separate components and features that may be readily separated from or combined with any feature of several other embodiments without departing from the scope or spirit of the present invention. All such modifications are intended to fall within the scope of the claims associated with this disclosure.

[0411] The present invention includes methods that can be performed using the subject device. The method can include the act of providing such a suitable device. Such providing can be performed by a user. In other words, the "providing" act merely requires the user to obtain, access, approach, locate, set up, activate, turn on, or otherwise provide the necessary device in the method. The methods described herein can be performed in any order of the events that are logically possible and in the order of the events recited.

[0412] The exemplary aspects of the present invention and details regarding material selection and manufacturing have been set forth above. Regarding other details of the present invention, these can be understood in conjunction with the patents and publications referenced above and what is generally known or understood by those skilled in the art. The same holds true for additional acts that are typically or logically utilized in aspects of the underlying method according to the present invention.

[0413] For ease of description, various terms indicating the relative positions of features are used herein. For example, various features can be described as being "above", "over", "on one side" of "higher" or "lower" other features. Other terms of relative position can also be used. All such terms of relative position assume that the polymeric structure or system formed by the features as a whole is in a certain orientation as a reference point for the purpose of description, but it should be understood that when in use, the structure can be placed laterally, flipped, or in any other orientation.

[0414] In addition, although the present invention has been described with reference to several examples optionally incorporating various features, the present invention is not limited to the invention described or indicated for each variant of the present invention. Various changes can be made to the described present invention without departing from the true spirit and scope of the present invention, and equivalents can be substituted (for the sake of brevity, whether or not included herein). Further, in the case where a range of values is provided, it should be understood that each intermediate value between the upper and lower limits of the range and any other stated or intermediate value within the stated range are included in the present invention.

[0415] In addition, it is contemplated that any optional features of the described variants of the present invention can be stated and claimed independently or in combination with any one or more of the features described herein. The recitation of a singular item includes the plural of the same item that may exist. More specifically, as used herein and in the associated claims, the singular forms "a", "an", "the", and "said" include plural objects unless otherwise expressly stated. In other words, in the above description and in the claims associated with this disclosure, the use of the article "at least one" for the claimed item is allowed. Further, it should be noted that such claims can be drafted to exclude any optional elements. Thus, in conjunction with claim elements or the use of "negative" limitations, this statement is intended as a precursor basis for the use of exclusive terms such as "individually", "only", etc.

[0416] Without using such exclusive terms, the term "comprising" in the claims associated with this disclosure shall be allowed to include any additional elements, regardless of whether a given number of elements are recited in such claims or an added feature can be considered to change the nature of the elements recited in the claims. Except as specifically defined herein, all technical and scientific terms used herein shall be given as broad a general understanding as possible while maintaining the validity of the claims.

[0417] The breadth of the present invention is not limited to the provided embodiments and / or the subject specification, but is defined only by the scope of the claim language associated with this disclosure. In fact, the novel devices, methods, and systems described herein may be embodied in many other forms. Additionally, various omissions, substitutions, and changes may be made to the forms of the methods and systems described herein without departing from the spirit of this disclosure. For example, while the blocks are presented in a given arrangement, alternative embodiments may perform similar functions with different components and / or circuit topologies, and some blocks may be deleted, moved, added, subdivided, combined, and / or modified. Each of these blocks may be implemented in a variety of different ways. Any suitable combination of the elements and actions of the various embodiments described above may be combined to provide other embodiments. The various features and processes described above may be implemented independently of each other or may be combined in various ways. All suitable combinations and subcombinations of the features of this disclosure are intended to fall within the scope of this disclosure.

Claims

1. A method of manufacturing an optical element, comprising: providing a substrate having a first refractive index and being transparent in the visible spectrum; forming a periodically repeating polymer structure on the substrate; and exposing the substrate to a metal precursor and then to an oxidation precursor, wherein the exposure is performed under pressure and temperature such that an inorganic material of a metal including the metal precursor is incorporated into the periodically repeating polymer structure, thereby forming a pattern of a periodically repeating optical structure configured to diffract visible light, the optical structure having a second refractive index greater than the first refractive index.

2. An optical element, comprising: a substrate having a first refractive index and being transparent in the visible spectrum; and a pattern of a periodically repeating optical structure formed on the substrate and configured to diffract visible light, the optical structure having a second refractive index greater than the first refractive index and comprising a polymer material in which an inorganic material is incorporated, wherein the inorganic material includes a metal oxide.

3. The optical element according to claim 2, wherein, the polymer material has a bulk refractive index less than the second refractive index, and the inorganic material has a bulk refractive index higher than the second refractive index.

4. The optical element according to claim 2, wherein, the second refractive index is greater than 1.7 and is at least 0.2 greater than the first refractive index.

5. The optical element according to claim 2, wherein, the substrate has a refractive index greater than 1.

5.

6. The optical element according to claim 2, wherein, the polymer material includes a photoresist.

7. The optical element according to claim 2, wherein, the inorganic material includes a transition metal oxide.

8. The optical element according to claim 2, wherein, the metal oxide includes an oxide selected from the group consisting of: alumina, zinc oxide, zirconia, hafnium oxide, or titanium oxide.

9. The optical element according to claim 2, wherein, the inorganic material is incorporated into a surface region of the optical structure, and a core region of the optical structure does not have the inorganic material incorporated therein.

10. The optical element according to claim 2, wherein, adjacent optical structures in the periodically repeating optical structure are spaced apart, and a surface of the substrate in the space does not have the inorganic material disposed thereon.

11. The optical element according to claim 2, wherein, adjacent optical structures in the periodically repeating optical structure are spaced apart, and a surface of the substrate in the space has a polymer material layer formed thereon in which the inorganic material is incorporated, the layer having a thickness less than a height of the optical structure.

12. The optical element according to claim 11, wherein, the entire thickness of the polymer material layer formed in the space is incorporated with the inorganic material.

13. The optical element according to claim 11, wherein, The polymer material layer formed in the space has a partial thickness that binds to the inorganic material in the surface region and a partial thickness that does not bind to the inorganic material.

14. The optical element according to claim 2, wherein, the substrate is configured such that visible light diffracted by the periodically repeating optical structure propagates under total internal reflection.

15. The optical element according to claim 2, wherein, the periodically repeating optical structure includes a metasurface.

16. The optical element according to claim 2, wherein, the substrate is configured such that visible light is guided therein under total internal reflection and diffracted out of the substrate by the periodically repeating optical structure.

17. The optical element according to claim 2, wherein, the substrate is configured such that visible light is guided therein under total internal reflection and diffracted by the periodically repeating optical structure so as to change the direction of propagation of the light beam through total internal reflection within the substrate.

18. An optical system, comprising: an optical element, comprising: a substrate having a first refractive index and being transparent in the visible spectrum, and a pattern of periodically repeating optical structures formed on the substrate and configured to diffract visible light, the optical structures having a second refractive index greater than the first refractive index and comprising a polymer material in which an inorganic material is incorporated, wherein the inorganic material includes a metal oxide, wherein the periodically repeating optical structure includes nanobeams arranged as a metasurface, the metasurface including a plurality of repeating unit cells, each unit cell including: a first group of nanobeams formed by one or more first nanobeams; and a second group of nanobeams formed by one or more second nanobeams, the one or more second nanobeams being adjacent to the one or more first nanobeams and spaced apart from each other by a sub-wavelength interval, wherein the one or more first nanobeams and the plurality of second nanobeams extend in different orientation directions.

19. The optical system according to claim 18, wherein, the unit cells repeat with a period less than or equal to 10 nm to 1 μm.

20. The optical system according to claim 18, wherein, the one or more first nanobeams and the one or more second nanobeams are oriented at an angle relative to each other to cause a phase difference between the visible light diffracted by the one or more first nanobeams and the visible light diffracted by the second nanobeams.

21. The optical system according to claim 18, wherein, the one or more first nanobeams and the one or more second nanobeams are oriented in orientation directions that are rotated 90 degrees relative to each other.

22. The optical system according to claim 18, wherein, the unit cells repeat with a period less than or equal to the wavelength of the visible light, wherein the wavelength is within the visible spectrum.

23. The optical system according to claim 18, wherein, the one or more first nanobeams and the one or more second nanobeams have a height less than the wavelength of the visible light.

24. An optical system includes a waveguide configured to propagate visible light, the optical system comprising: a substrate having a first refractive index and being transparent in the visible spectrum so that light can be guided therein by total internal reflection; and a pattern of periodically repeated optical structures formed on the substrate and configured to diffract visible light, the optical structures having a second refractive index greater than the first refractive index and comprising a polymeric material in which an inorganic material is incorporated, wherein the inorganic material comprises a metal oxide, wherein the periodically repeated optical structures are arranged to diffract light at a diffraction angle with respect to the direction of incident light and cause the diffracted light to propagate in the substrate under total internal reflection, or are arranged to diffract the light guided in the substrate under total internal reflection at a diffraction angle with respect to the direction of the light guided in the substrate.

25. The optical system according to claim 24, wherein, the polymeric material has a bulk refractive index less than the second refractive index, and the inorganic material has a bulk refractive index higher than the second refractive index.

26. The optical system according to claim 24, wherein, the second refractive index is greater than 1.7 and is at least 0.2 greater than the first refractive index.

27. The optical system according to claim 24, wherein, the diffraction angle exceeds 50 degrees.

28. The optical system according to claim 24, further comprising a light source configured to emit light of a wavelength to the pattern of the periodically repeated optical structures.

29. The optical system according to claim 28, further comprising a spatial light modulator configured to modulate the light from the light source and output the modulated light to the pattern of the periodically repeated optical structures.

30. The optical system according to claim 24, wherein, the periodically repeated optical structures are arranged to diffract light at a diffraction angle with respect to the direction of the incident light and cause the diffracted light to propagate in the substrate under total internal reflection.

31. The optical system according to claim 24, wherein, the periodically repeated optical structures are arranged to diffract the light guided in the substrate under total internal reflection at a diffraction angle with respect to the direction of the light guided in the substrate.

32. The optical system according to claim 31, wherein, the periodically repeated optical structures are arranged to diffract the light guided in the substrate under total internal reflection out of the substrate.

33. A head-mounted display device configured to project light onto a user's eyes to display augmented reality image content, the head-mounted display device comprising: a frame configured to be supported on a user's head; a display disposed on the frame, at least a portion of the display comprising: One or more waveguides, the one or more waveguides including a transparent portion and being disposed in a position in front of the user's eyes when the user wears the head-mounted display device such that the transparent portion transmits light from a portion of the environment in front of the user to the user's eyes to provide a view of the portion of the environment in front of the user; One or more light sources; and At least one diffraction grating configured to couple light from the light source into the one or more waveguides or to couple light out of the one or more waveguides, the diffraction grating including: A substrate having a first refractive index and being transparent in the visible spectrum; and A pattern of periodically repeating optical structures formed on the substrate and configured to diffract visible light, the optical structures having a second refractive index greater than the first refractive index and including a polymer material in which an inorganic material is incorporated, wherein the inorganic material includes a metal oxide.

34. The apparatus according to claim 33, wherein, The one or more light sources include a fiber optic scanning projector.

35. The apparatus according to claim 33, the display being configured to project light into the user's eyes to present image content to the user on a plurality of depth planes.

36. A method of manufacturing an optical element, comprising: Providing a substrate that is transparent in the visible spectrum; Forming a periodically repeating polymer structure having a first refractive index on the substrate; and Exposing the substrate to a metal precursor and then to an oxidation precursor, wherein the exposure is performed under pressure and temperature such that an inorganic material of a metal including the metal precursor is incorporated into the periodically repeating polymer structure, thereby increasing the refractive index of the periodically repeating polymer structure to form a pattern of periodically repeating optical structures configured to diffract visible light.

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