Method for processing a diffraction grating

Abstract

A method for fabricating a blazed diffraction grating includes providing a master template substrate and imprinting periodically repeating lines onto the master template substrate in a plurality of master template regions, the periodically repeating lines in different ones of the master template regions extending in different directions. The method additionally includes imprinting at least one blazed diffraction grating pattern onto the grating substrate using at least one of the master template regions as a master template.

Description

Technical Field

[0001] (Cross - Reference to Related Applications) This application claims the benefit of priority of U.S. Provisional Application No. 62 / 876,241, filed on July 19, 2019, entitled "METHOD OF FABRICATING DIFFRACTION GRATINGS", the content of which is incorporated herein by reference in its entirety. (Incorporation by Reference)

[0002] This application incorporates by reference in their entireties the following patent applications: U.S. Patent Application No. 14 / 555,585, filed on November 27, 2014, and published as U.S. Patent Publication No. 2015 / 0205126 on July 23, 2015; U.S. Patent Application No. 14 / 690,401, filed on April 18, 2015, and published as U.S. Patent Publication No. 2015 / 0302652 on October 22, 2015; U.S. Patent Application No. 14 / 212,961, filed on March 14, 2014, and issued as U.S. Patent No. 9,417,452 on August 16, 2016; and U.S. Patent Application No. 14 / 331,218, filed on July 14, 2014, and published as U.S. Patent Publication No. 2015 / 0309263 on October 29, 2015.

[0003] This disclosure relates to display systems, and more particularly to augmented and virtual reality display systems.

Background Art

[0004] (Description of Related Technologies) Modern computing and display technologies have facilitated the development of systems for so-called "virtual reality" or "augmented reality" experiences, where digitally reproduced images or portions thereof are presented to a user in a manner that appears or can be perceived as being real. Virtual reality, i.e., the "VR" scenario, typically involves the presentation of digital or virtual image information without transparency to other actual real-world visual inputs, and augmented reality, i.e., the "AR" scenario, typically involves the presentation of digital or virtual image information as an augmentation to the visualization of the actual world around the user. Mixed reality, i.e., the "MR" scenario, is a type of AR scenario and typically involves virtual objects integrated into and responsive to the natural world. For example, in an MR scenario, AR image content can be perceived as being blocked by or otherwise interacting with objects within the real world.

[0005] Referring to FIG. 1, an augmented reality scene 10 is depicted, and to a user of AR technology, a real-world park-like setting 20 characterized by people, trees, buildings in the background, and a concrete platform 30 is visible. In addition to these items, a user of AR technology also "sees" and perceives as "visible" a robot image 40 standing on the real-world platform 30 and "virtual content" such as a flying comic-like avatar character 50 that appears anthropomorphic like a honeybee, but these elements 40, 50 do not exist in the real world. The human visual perception system is complex, and it is difficult to produce AR technology that facilitates a comfortable, natural, and rich presentation of virtual image elements among other virtual or real-world image elements.

[0006] The systems and methods disclosed herein address various challenges associated with AR and VR technologies. SUMMARY OF THE INVENTION MEANS FOR SOLVING THE PROBLEM

[0007] In one aspect, a method of fabricating a blazed diffraction grating includes providing a master template substrate and imprinting periodically repeated lines on the master template substrate within a plurality of master template regions. The periodically repeated lines within different ones of the master template regions extend in different directions. The method further includes using at least one of the master template regions as a master template to imprint at least one blazed diffraction grating pattern on a grating substrate.

[0008] In another aspect, a method of fabricating a master template for imprinting a blazed diffraction grating includes providing a master template substrate and providing a primary master template formed on the primary master substrate and including periodically repeated lines. The method further includes using the primary master template within a plurality of master template regions to imprint the periodically repeated lines on the master template substrate. The periodically repeated lines within different ones of the master template regions extend in different directions.

[0009] In yet another aspect, a method of fabricating a diffraction grating includes providing a master template substrate. The method further includes imprinting periodically repeated lines on the master template substrate within one or more master template regions, wherein the periodically repeated lines are formed from a first material. The method further includes coating the periodically repeated lines with a second material having a hardness greater than the first material. The method further includes using one or more of the master template regions as a master template to imprint one or more blazed diffraction grating patterns on a grating substrate. The present invention provides, for example, the following. (Item 1) A method for processing a blazed diffraction grating, the method comprising: providing a master template substrate; imprinting lines that are periodically repeated on the master template substrate within a plurality of master template regions, wherein the lines that are periodically repeated within different ones of the master template regions extend in different directions; using at least one of the master template regions as a master template to imprint at least one blazed diffraction grating pattern on a grating substrate A method comprising. (Item 2) The method according to Item 1, wherein the lines that are periodically repeated within different ones of the master template regions extend in non-orthogonal directions. (Item 3) The method according to Item 1, wherein the lines that are periodically repeated within adjacent ones of the master template regions extend in directions forming an angle of 0 to 90 degrees. (Item 4) The method according to Item 1, wherein the lines that are periodically repeated within different ones of the master template regions extend in different radial directions with respect to the central axis of the master template substrate. (Item 5) The method according to Item 1, wherein imprinting the lines that are periodically repeated on the master template substrate includes imprinting within at least four master template regions. (Item 6) The method according to Item 1, wherein imprinting the lines that are periodically repeated includes imprinting across the silicon surface of the master template substrate. (Item 7) The method according to Item 1, wherein imprinting the lines that are periodically repeated includes imprinting across the silicon oxide surface of the master template substrate. (Item 8) The method according to Item 1, wherein imprinting the lines that are periodically repeated on the master template substrate includes sequentially imprinting within different ones of the plurality of master template regions using the same primary master template. (Item 9) The method according to Item 1, wherein the lines that are periodically repeated formed on the master template substrate have a sawtooth profile. (Item 10) The method according to item 1, wherein the periodically repeated lines formed on the master template substrate comprise symmetric opposing side surfaces that form a similar angle with respect to the plane of the master template substrate. (Item 11) The method according to item 1, wherein the periodically repeated lines formed on the master template substrate comprise asymmetric opposing side surfaces that form different angles with respect to the plane of the master template substrate. (Item 12) The method according to item 1, wherein the periodically repeated lines formed on the master template substrate comprise opposing side surfaces having different inclinations with respect to the plane of the major surface of the master template substrate. (Item 13) The method according to item 1, wherein the periodically repeated lines formed on the master template substrate comprise side surfaces having a stepped structure. (Item 14) The method according to item 1, wherein the periodically repeated lines formed on the master template substrate contain a polymer material. (Item 15) The method according to item 1, wherein the periodically repeated lines formed on the master template substrate contain a dielectric material. (Item 16) The method according to item 1, further comprising coating the periodically repeated lines formed on the master template substrate with a dielectric material. (Item 17) The method according to item 1, further comprising coating the periodically repeated lines formed on the master template substrate with a metal oxide or a metal nitride. (Item 18) The method according to item 1, further comprising coating the periodically repeated lines formed on the master template substrate with a metal or a metal alloy. (Item 19) The method according to item 1, further comprising transferring the pattern corresponding to the periodically repeated lines into the master template substrate. (Item 20) The method according to item 19, wherein transferring the pattern comprises dry-etching the master template substrate using the periodically repeated lines as a partial mask. (Item 21) The method according to item 20, wherein the dry-etching comprises locally dry-etching the master template region. (Item 22) Imprinting the periodically repeated lines includes imprinting using a primary master template having periodically repeated lines formed on a primary master substrate, the method according to item 1. (Item 23) The periodically repeated lines formed on the primary master substrate have a sawtooth profile, the method according to item 22. (Item 24) The periodically repeated lines formed on the primary master substrate have laterally surfaces that are asymmetrically oriented, the method according to item 22. (Item 25) The primary master substrate comprises a silicon substrate, the method according to item 22. (Item 26) The primary master substrate is a silicon substrate having a major surface with a (311) crystal orientation, the method according to item 22. (Item 27) The periodically repeated lines formed on the primary master substrate have facets with a (111) crystal orientation, the method according to item 26. (Item 28) The method according to item 25 further includes forming the primary master template by lithographically patterning and etching the silicon substrate. (Item 29) Etching the silicon substrate includes wet etching, the method according to item 28. (Item 30) The periodically repeated lines formed on the primary master substrate include a polymer material coated with a dielectric material, the method according to item 22. (Item 31) The grating substrate is a transparent substrate, the method according to item 1. (Item 32) The grating substrate has a refractive index greater than about 1.4, the method according to item 1. (Item 33) The grating substrate comprises a waveguide, the method according to item 1. (Item 34) The blazed diffraction grating comprises an internal coupling grating configured to internally couple light into the waveguide, the method according to item 33. (Item 35) The blazed diffraction grating comprises an external coupling grating configured to externally couple light from the waveguide, the method according to item 33. (Item 36) The blazed diffraction grating comprises a light dispersion element configured to disperse light and propagate it towards an external coupling element within the waveguide, the method according to item 33. (Item 37) The method according to item 33, wherein the blazed diffraction grating is configured to disperse light and propagate in the waveguide, and further serves as a combined external coupling grating and a light dispersion element configured to couple light from the waveguide to the outside. (Item 38) The method according to item 1, wherein the blazed diffraction grating pattern has a geometric shape configured to have a first-order diffraction efficiency exceeding 50% for at least one polarization of light. (Item 39) The method according to item 1, wherein imprinting at least one blazed diffraction grating pattern includes simultaneously imprinting two or more blazed diffraction grating patterns. (Item 40) The method according to item 1, wherein the grating substrate has a refractive index greater than 1.9. (Item 41) The grating substrate is ZrO 2 , TiO 2 , SiC, or formed from a Li-based oxide, according to the method of item 1. (Item 42) The method according to item 1, wherein the at least one blazed diffraction grating pattern comprises a plurality of straight lines. (Item 43) The method according to item 1, wherein the at least one blazed diffraction grating pattern comprises a plurality of discontinuous lines. (Item 44) The method according to item 1, wherein the at least one blazed diffraction grating pattern comprises a plurality of pillars protruding from the surface of the grating substrate. (Item 45) The method according to item 1, wherein the at least one blazed diffraction grating pattern comprises a plurality of straight lines, and at least some of the straight lines have different widths. (Item 46) The method according to item 1, wherein the at least one blazed diffraction grating pattern comprises diffraction features arranged as a one-dimensional (1D) array having periodicity in one lateral direction. (Item 47) The method according to item 46, wherein the 1D array serves as a 1D grating configured to preferentially diffract light in one direction. (Item 48) The method according to item 1, wherein the at least one blazed diffraction grating pattern comprises diffraction features arranged as a two-dimensional (2D) array having periodicity in two lateral directions. (Item 49) The method according to item 48, wherein the 2D array serves as a 2D grating configured to preferentially diffract light in two directions. (Item 50) The method according to item 48, wherein the 2D array has the same number of diffraction features in two different lateral directions. (Item 51) A method of processing a master template for imprinting a blazed diffraction grating, the method comprising: providing a master template substrate; providing a primary master template comprising periodically repeated lines formed on a primary master substrate; using the primary master template within a plurality of master template regions to imprint the periodically repeated lines onto the master template substrate, wherein the periodically repeated lines within different ones of the master template regions extend in different directions; A method as described above. (Item 52) The method according to item 51, wherein the periodically repeated lines formed on the primary master substrate have a sawtooth profile. (Item 53) The method according to item 51, wherein the periodically repeated lines formed on the primary master substrate have laterally surfaces that are asymmetrically oriented. (Item 54) The method according to item 51, wherein the primary master substrate is a silicon substrate having a major surface with a (311) crystal orientation. (Item 55) The method according to item 54, wherein the periodically repeated lines formed on the primary master substrate have facets with a (111) crystal orientation. (Item 56) The method according to item 51, wherein providing the primary master template includes lithographically patterning and etching the periodically repeated lines into a silicon substrate. (Item 57) The method according to item 56, wherein etching the silicon substrate includes wet etching. (Item 58) The method according to item 51, wherein providing the primary master template includes forming the periodically repeated lines including a polymer material and coating the periodically repeated lines with a dielectric material. (Item 59) The method according to item 51, wherein the periodically repeated lines within different ones of the master template regions extend in non-orthogonal directions. (Item 60) The method according to item 51, wherein the periodically repeated lines within different ones of the master template regions extend in a direction radially symmetric with respect to the central axis of the master template substrate. (Item 61) The method according to item 51, wherein imprinting the periodically repeated lines onto the master template substrate includes imprinting within at least four master template regions. (Item 62) The method according to item 51, wherein the periodically repeated lines formed on the master template substrate have a sawtooth profile. (Item 63) The method according to item 51, wherein the periodically repeated lines formed on the master template substrate have an asymmetric side surface. (Item 64) The method according to item 51, wherein the periodically repeated lines formed on the master template substrate have opposing side surfaces with different inclinations with respect to the plane of the major surface of the master template substrate. (Item 65) The method according to item 51, wherein the periodically repeated lines formed on the master template substrate have a stepped side surface. (Item 66) The method according to item 51, wherein the periodically repeated lines formed on the master template substrate contain a polymer material. (Item 67) The method according to item 51, wherein the periodically repeated lines formed on the master template substrate contain a dielectric material. (Item 68) The method according to item 51, further comprising coating the periodically repeated lines formed on the master template substrate with a dielectric material. (Item 69) The method according to item 51, further comprising coating the periodically repeated lines formed on the master template substrate with a metal oxide or a metal nitride. (Item 70) The method according to item 51, further comprising coating the periodically repeated lines formed on the master template substrate with a metal or a metal alloy. (Item 71) The method according to item 51, further comprising transferring a pattern corresponding to the periodically repeated lines into the master template substrate. (Item 72) The method according to item 71, wherein transferring the pattern includes dry etching the master template substrate. (Item 73) The method according to item 72, wherein dry etching includes locally dry etching the master template region. (Item 74) A method of machining a diffraction grating, the method comprising: providing a master template substrate; and imprinting periodically repeated lines in one or more master template regions on the master template substrate, the periodically repeated lines being formed from a first material. Coating the periodically repeated lines with a second material having a hardness greater than that of the first material; Using one or more master template regions as a master template to imprint one or more blazed diffraction grating patterns on a grating substrate; A method comprising. (Item 75) Imprinting the periodically repeated lines includes imprinting in a plurality of master template regions, and the periodically repeated lines in different ones of the master template regions extend in different directions. The method according to item 74. (Item 76) The periodically repeated lines in different ones of the master template regions extend in different radial directions with respect to the central axis of the master template substrate. The method according to item 74. (Item 77) Imprinting the periodically repeated lines on the master template substrate includes imprinting in at least four master template regions. The method according to item 74. (Item 78) The periodically repeated lines formed on the master template substrate have an asymmetric side surface. The method according to item 74. (Item 79) The periodically repeated lines formed on the master template substrate include a polymer material. The method according to item 74. (Item 80) The periodically repeated lines formed on the master template substrate include a dielectric material. The method according to item 74. (Item 81) The method according to item 74, further comprising coating the periodically repeated lines formed on the master template substrate with a dielectric material. (Item 82) The method according to item 74, further comprising coating the periodically repeated lines formed on the master template substrate with a metal oxide or a metal nitride. (Item 83) The method according to item 74, further comprising coating the periodically repeated lines formed on the master template substrate with a metal or a metal alloy. (Item 84) The grating substrate has a refractive index greater than 1.9. The method according to item 74. (Item 85) The grating substrate is made of ZrO 2 , TiO 2 , SiC, or a Li-based oxide. The method according to item 74.

Brief Description of the Drawings

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[0042] Throughout the drawings, reference numbers may be reused to indicate correspondence between referenced elements. The drawings are provided to illustrate the exemplary embodiments described herein and are not intended to limit the scope of the present disclosure.

DETAILED DESCRIPTION

[0043] Detailed Description An AR system can display virtual content to a user or viewer while still enabling the user to see the world around them. Preferably, this content is displayed on a head-mounted display that is part of eyewear, for example, by projecting image information onto the user's eyes. Additionally, the display can also transmit light from the surrounding environment to the user's eyes, enabling a view of the surrounding environment. As used herein, it should be understood that a "head-mounted" or "head-mountable" display is a display that can be mounted on the head of a viewer or user.

[0044] The various AR systems disclosed herein include a virtual / augmented / composite display, which can in turn include one or more optical elements formed on or as part of a waveguide. The optical elements can include, for example, internal coupling optical elements that can be employed to couple light into the waveguide, and / or external coupling optical elements that can be employed to couple light out of the waveguide and into the user's eye. To achieve high efficiency in the internal coupling of light into the waveguide and / or the external coupling of light therefrom, the optical elements can include diffraction gratings. In some display systems, the relatively high diffraction efficiency of the optical elements is achieved in part by including a blazed diffraction grating, which is a type of diffraction grating optimized to achieve an improved diffraction efficiency for a given diffraction order such that the refractive power is improved or maximized for that given diffraction order. The improved diffraction efficiency for a given diffraction order is in turn achieved in some blazed diffraction gratings by having faceted features, such as faceted lines. A blazed diffraction grating having faceted features such as lines can be fabricated by imprinting the blazed diffraction grating pattern onto a device substrate, such as a waveguide, using a device master template. As a result, the manufacturing throughput can be limited by the number of blazed diffraction grating patterns that can be simultaneously imprinted onto the device substrate by the device master template. Advantageously, in the manufacturing techniques described herein, the device master template is configured to simultaneously imprint a relatively large number of blazed diffraction grating patterns onto the device substrate, thereby enabling a relatively high manufacturing throughput of blazed diffraction gratings. In particular, in the disclosed techniques, a device master template having blazed diffraction patterns extending in a plurality of directions, such as radially, is manufactured, which enables an efficient use of the area of the device master template for high-throughput parallel imprinting of blazed diffraction patterns onto a device substrate such as a waveguide.

[0045] Reference will now be made to the drawings, where like reference numerals refer to like parts throughout. Unless otherwise indicated, the drawings are schematic and are not necessarily drawn to scale.

[0046] FIG. 2 illustrates a conventional display system for simulating a three-dimensional image for a user. It should be understood that when the user's eyes are separated and looking at an actual object in space, each eye has a slightly different view of the object and can form an image of the object at different locations on the retina of each eye. This can be referred to as binocular disparity and can be utilized by the human visual system to provide a perception of depth. The conventional display system simulates binocular disparity by presenting two distinct images 190, 200 with slightly different views of a single identical virtual object, one for each of the eyes 210, 220, corresponding to the views of the virtual object that would be seen by each eye as if the virtual object were an actual object at the desired depth. These images provide binocular cues that can be interpreted by the user's visual system to derive a perception of depth.

[0047] Continuing to refer to FIG. 2, the images 190, 200 are separated from the eyes 210, 220 by a distance 230 on the z-axis. The z-axis is parallel to the optical axis of the viewer in a state where the eye is fixated on an object at optical infinity directly in front of the viewer. The images 190, 200 are flat and at a fixed distance from the eyes 210, 220. Based on the slightly different views of the virtual object within the images presented to the eyes 210, 220 respectively, the eyes can necessarily rotate so that the image of the object comes to corresponding points on the respective retinas of the eyes and a single binocular vision is maintained. This rotation can converge the respective lines of sight of the eyes 210, 220 onto a point in the space where the virtual object is perceived to exist. As a result, the provision of a three-dimensional image has conventionally involved manipulating the convergence / divergence movement of the user's eyes 210, 220 and providing binocular cues that are interpreted by the human visual system to provide a perception of depth.

[0048] However, the generation of realistic and comfortable perception of depth is difficult. It should be understood that light from objects at different distances from the eye has wavefronts with different amounts of divergence. FIGS. 3A-3C illustrate the relationship between distance and divergence of light rays. The distances between the object and the eye 210 are represented in the order of decreasing distances R1, R2, and R3. As shown in FIGS. 3A-3C, the light rays diverge more as the distance to the object decreases. Conversely, as the distance increases, the light rays become more collimated. In other words, it can be said that the light field generated by a point (object or part of an object) has a spherical wavefront curvature that is a function of the distance the point is away from the user's eye. The curvature increases as the distance between the object and the eye 210 decreases. Only one eye 210 is illustrated in FIGS. 3A-3C and other figures in this specification for clarity of illustration, but the discussion regarding the eye 210 can be applied to both eyes 210 and 220 of the viewer.

[0049] Continuing to refer to FIGS. 3A-3C, light from the object on which the viewer's eye is fixated can have different degrees of wavefront divergence. Due to the different amounts of wavefront divergence, the light can be focused differently by the lens of the eye, which in turn can require the lens to take on different shapes to form a focused image on the retina of the eye. When a focused image is not formed on the retina, the resulting retinal blur acts as a cue for accommodation, causing a change in the shape of the lens of the eye until a focused image is formed on the retina. For example, the cue for accommodation induces relaxation or contraction of the ciliary muscle surrounding the lens of the eye, thereby modulating the force applied to the zonular fibers that hold the lens, and thus changing the shape of the lens of the eye until the retinal blur of the fixated object is eliminated or minimized, thereby forming a focused image of the fixated object on the retina (e.g., fovea) of the eye. The process by which the lens of the eye changes shape can be referred to as accommodation, and the shape of the lens of the eye required to form a focused image of the fixated object on the retina (e.g., fovea) of the eye can be referred to as the accommodative state.

[0050] Referring now to FIG. 4A, the representation of the accommodation - convergence / divergence response of the human visual system is illustrated. Eye movements to fixate an object cause the eye to receive light from the object, and the light forms an image on each of the retinas of the eye. The presence of retinal blur in the image formed on the retina can provide a cue for accommodation, and the relative location of the image on the retina can provide a cue for convergence / divergence. The cue for accommodation causes accommodation to occur, causing the lens of the eye to assume a particular accommodation state that forms a focused image of the object on the retina of the eye (e.g., the fovea). On the other hand, the cue for convergence / divergence causes convergence / divergence movement (rotation of the eye) such that the images formed on each retina of each eye are at corresponding retinal points that maintain single binocular vision. At these positions, it can be said that the eye is in a particular convergence / divergence state. Continuing to refer to FIG. 4A, accommodation can be understood as the process by which the eye achieves a particular accommodation state, and convergence / divergence can be understood as the process by which the eye achieves a particular convergence / divergence state. As shown in FIG. 4A, the accommodation and convergence / divergence states of the eye can change when the user fixates on another object. For example, the accommodated state can change when the user fixates on a new object at a different depth along the z - axis.

[0051] Without being limited by theory, it is believed that the viewer of an object can perceive the object as "three - dimensional" due to the combination of convergence / divergence and accommodation. As described above, the convergence / divergence of the two eyes with respect to each other (e.g., the movement of the pupils towards or away from each other, the rotation of the eyes to converge the lines of sight and fixate on an object) is closely associated with the accommodation of the lens of the eye. Under normal conditions, a change in the shape of the lens of the eye to change focus from one object to another object at a different distance will automatically cause a corresponding change in convergence / divergence to the same distance under a relationship known as the "accommodation - convergence / divergence reflex". Similarly, a change in convergence / divergence will, under normal conditions, induce a corresponding change in the shape of the lens.

[0052] Referring now to FIG. 4B, examples of different accommodation and convergence / divergence movement states of the eyes are illustrated. A pair of eyes 222a fixates on an object at optical infinity, while a pair of eyes 222b fixates on an object 221 at less than optical infinity. It should be noted that the convergence / divergence movement states of each pair of eyes are different, with a pair of eyes 222a being directed straight, while a pair of eyes 222 converges onto the object 221. The accommodation states of the eyes forming each pair of eyes 222a and 222b are also different, as represented by the different shapes of the crystalline lenses 210a, 220a.

[0053] Unfortunately, many users of conventional "3-D" display systems find such conventional systems uncomfortable or do not perceive any sense of depth at all due to the mismatch between accommodation and convergence / divergence movement states in these displays. As described above, many stereoscopic or "3-D" display systems display a scene by providing slightly different images to each eye. Such systems are uncomfortable for many viewers because they merely provide different presentations of the scene, causing a change in the convergence / divergence movement state of the eyes, but without a corresponding change in the accommodation state of those eyes. Rather, the images are presented at a fixed distance from the eyes by the display such that the eyes view all the image information in a single accommodation state. Such an arrangement goes against the "accommodation-convergence / divergence reflex" by causing a change in the convergence / divergence movement state without a corresponding change in the accommodation state. This mismatch is thought to cause discomfort to the viewer. A display system that provides a better match between accommodation and convergence / divergence can form a more realistic and comfortable simulation of a three-dimensional image.

[0054] Although not limited by theory, the human eye is typically thought to be able to interpret a finite number of depth planes and provide depth perception. As a result, a highly realistic simulation of the perceived depth can be achieved by providing different presentations of an image corresponding to each of these limited number of depth planes to the eye. In some embodiments, the different presentations provide both cues for convergence / divergence motion and corresponding cues for accommodation, thereby providing a physiologically correct accommodation-convergence / divergence match.

[0055] Continuing to refer to FIG. 4B, two depth planes 240 corresponding to different distances in space from eyes 210, 220 are illustrated. For a given depth plane 240, convergence / divergence motion cues may be provided by appropriately displaying images from different viewpoints for each of eyes 210, 220. Additionally, for a given depth plane 240, the light forming the images provided to each eye 210, 220 may have a wavefront divergence corresponding to a light field generated by a point at the distance of that depth plane 240.

[0056] In the illustrated embodiment, the distance along the z-axis of depth plane 240 containing point 221 is 1 m. As used herein, the distance or depth along the z-axis may be measured using a zero point located at the exit pupil of the user's eye. Thus, a depth plane 240 located at a depth of 1 m corresponds to a distance 1 m away from the exit pupil of the user's eye on the optical axis of those eyes with the eyes directed towards optical infinity. As an approximation, the depth or distance along the z-axis is measured from the front of the display of the user's eye (e.g., from the surface of the waveguide), and a value related to the distance between the device and the exit pupil of the user's eye may be added. That value may be referred to as the pupil distance and corresponds to the distance between the exit pupil of the user's eye and the display worn by the user in front of the eye. In practice, the value for the pupil distance may generally be a normalized value used for all viewers. For example, the pupil distance may be assumed to be 20 mm, and the depth plane at a depth of 1 m may be at a distance of 980 mm in front of the display.

[0057] Referring now to FIGS. 4C and 4D, examples of consistent vergence-accommodation - convergence / divergence motion distances and inconsistent vergence-accommodation - convergence / divergence motion distances are illustrated, respectively. As illustrated in FIG. 4C, the display system may provide an image of a virtual object to each eye 210, 220. The image may cause the eyes 210, 220 to assume a convergence / divergence motion state in which the eyes converge on a point 15 on the depth plane 240. In addition, the image may be formed by light having a wavefront curvature corresponding to the real object in that depth plane 240. As a result, the eyes 210, 220 assume an accommodation state in which the image is in focus on their retinas. Thus, the user may perceive the virtual object as being at the point 15 on the depth plane 240.

[0058] It should be understood that the accommodation and convergence / divergence motion states of the eyes 210, 220 are each associated with a specific distance on the z-axis. For example, an object at a specific distance from the eyes 210, 220 causes those eyes to assume a specific accommodation state based on the distance of the object. The distance associated with a specific accommodation state may be referred to as the accommodation distance A d Similarly, there exists a specific vergence distance V d associated with a specific convergence / divergence motion state or the eyes in a particular position relative to each other. When the accommodation distance and the vergence distance match, the relationship between accommodation and vergence can be said to be physiologically correct. This is considered to be the most comfortable scenario for the viewer.

[0059] However, in a stereoscopic display, the accommodation distance and the vergence / accommodation motion distance may not always match. For example, as shown in FIG. 4D, the images displayed to eyes 210, 220 may be displayed with wavefront divergence corresponding to depth plane 240, and eyes 210, 220 may be in a specific accommodation state where points 15a, 15b on that depth plane are in focus. However, the images displayed to eyes 210, 220 may provide a cue for vergence / accommodation motion that converges eyes 210, 220 onto a point 15 that is not located on depth plane 240. As a result, the accommodation distance, in some embodiments, corresponds to the distance from the exit pupils of eyes 210, 220 to depth plane 240, while the vergence / accommodation motion distance corresponds to a greater distance from the exit pupils of eyes 210, 220 to point 15. The accommodation distance is different from the vergence / accommodation motion distance. As a result, there is an accommodation-vergence / accommodation motion mismatch. Such a mismatch is considered undesirable and may cause discomfort to the user. The mismatch corresponds to a distance (e.g., V d -A d ) and it should be understood that it can be characterized using diopters.

[0060] It should be understood that in some embodiments, reference points other than the exit pupils of eyes 210, 220 can also be used to determine the distance for determining the accommodation-vergence / accommodation motion mismatch as long as the same reference point is used for the accommodation distance and the vergence / accommodation motion distance. For example, the distance can be measured from the cornea to the depth plane, from the retina to the depth plane, from the eyepiece (e.g., the waveguide of the display device) to the depth plane, etc.

[0061] Although not limited by theory, it is believed that a user may physiologically perceive vergence-accommodation motion mismatches of up to approximately 0.25 diopters, up to approximately 0.33 diopters, and up to approximately 0.5 diopters as being correct without the mismatch itself causing significant discomfort. In some embodiments, a display system disclosed herein (e.g., display system 250, FIG. 6) presents an image to a viewer having a vergence-accommodation motion mismatch of approximately 0.5 diopters or less. In some other embodiments, the vergence-accommodation motion mismatch of an image provided by the display system is approximately 0.33 diopters or less. In still other embodiments, the vergence-accommodation motion mismatch of an image provided by the display system is approximately 0.25 diopters or less, including approximately 0.1 diopters or less.

[0062] FIG. 5 illustrates a side view of an approach for simulating a three-dimensional image by modifying wavefront divergence. The display system includes a waveguide 270 configured to receive light 770 encoded with image information and output the light to the user's eye 210. The waveguide 270 may output light 650 with a defined amount of wavefront divergence corresponding to the wavefront divergence of a light field generated by a point on a desired depth plane 240. In some embodiments, the same amount of wavefront divergence is provided for all objects presented on that depth plane. Additionally, it will be shown that the user's other eye may be provided with image information from a similar waveguide.

[0063] In some embodiments, a single waveguide may be configured to output light with a set amount of wavefront divergence corresponding to a single or limited number of depth planes, and / or the waveguide may be configured to output light within a limited range of wavelengths. As a result, in some embodiments, multiple or stacked waveguides may be utilized to provide different amounts of wavefront divergence for different depth planes and / or to output light within different ranges of wavelengths. As used herein, it should be understood that a depth plane may follow the contour of a flat or curved surface.

[0064] FIG. 6 illustrates an example of a stack of waveguides for outputting image information to a user. The display system 250 includes a stack or stacked waveguide assembly 260 of waveguides that can be utilized to provide three-dimensional perception to the eye / brain using a plurality of waveguides 270, 280, 290, 300, 310. It should be understood that the display system 250 may be considered a light field display in some embodiments. Additionally, the waveguide assembly 260 may also be referred to as an eyepiece.

[0065] In some embodiments, the display system 250 may be configured to provide a substantially continuous cue for convergence / divergence movement and a plurality of discrete cues for depth adjustment. The cue for convergence / divergence movement may be provided by displaying different images to each of the user's eyes, and the cue for depth adjustment may be provided by outputting light that forms an image with a selectable discrete amount of wavefront divergence. In other words, the display system 250 may be configured to output light with a variable level of wavefront divergence. In some embodiments, each discrete level of wavefront divergence may correspond to a particular depth plane and may be provided by a particular one of the waveguides 270, 280, 290, 300, 310.

[0066] Continuing to refer to FIG. 6, waveguide assembly 260 may also include a plurality of features 320, 330, 340, 350 between the waveguides. In some embodiments, features 320, 330, 340, 350 may be one or more lenses. Waveguides 270, 280, 290, 300, 310, and / or the plurality of lenses 320, 330, 340, 350 may be configured to transmit image information to the eye using various levels of wavefront curvature or ray divergence. Each waveguide level may be associated with a particular depth plane and may be configured to output image information corresponding to that depth plane. Image input devices 360, 370, 380, 390, 400 may function as light sources for the waveguides and may be utilized to input image information into waveguides 270, 280, 290, 300, 310, respectively, configured to disperse incident light across each individual waveguide for output toward eye 210 as described herein. Light exits from output surfaces 410, 420, 430, 440, 450 of image input devices 360, 370, 380, 390, 400 and is input into corresponding input surfaces 460, 470, 480, 490, 500 of waveguides 270, 280, 290, 300, 310. In some embodiments, input surfaces 460, 470, 480, 490, 500 may each be an edge of the corresponding waveguide or a portion of a major surface of the corresponding waveguide (i.e., one of the waveguide surfaces facing directly toward world 510 or viewer's eye 210). In some embodiments, a single beam of light (e.g., a collimated beam) may be input into each waveguide and output an entire field of cloned collimated beams directed toward eye 210 at a particular angle (and divergence amount) corresponding to the depth plane associated with the particular waveguide. In some embodiments, a single one of image input devices 360, 370, 380, 390, 400 may be associated with and input light into a plurality (e.g., three) of waveguides 270, 280, 290, 300, 310.

[0067] In some embodiments, the image input devices 360, 370, 380, 390, 400 are discrete displays that each generate image information for input into their respective waveguides 270, 280, 290, 300, 310. In some other embodiments, the image input devices 360, 370, 380, 390, 400 are the output ends of a single multiplexed display that can send image information to each of the image input devices 360, 370, 380, 390, 400, for example, via one or more optical waveguides (such as optical fiber cables). It should be understood that the image information provided by the image input devices 360, 370, 380, 390, 400 can include light of different wavelengths or colors (e.g., different primary colors as discussed herein).

[0068] In some embodiments, the light input into the waveguides 270, 280, 290, 300, 310 is provided by an optical projector system 520 that includes an optical module 530 that can include a light emitter such as a light emitting diode (LED). The light from the optical module 530 can be directed via a beam splitter 550 to a light modulator 540, such as a spatial light modulator, and thereby modified. The light modulator 540 can be configured to vary the perceived intensity of the light input into the waveguides 270, 280, 290, 300, 310 and to encode the light with image information. Examples of spatial light modulators include liquid crystal displays (LCDs) including liquid crystal on silicon (LCOS) displays. The image input devices 360, 370, 380, 390, 400 are shown schematically and, in some embodiments, these image input devices can represent different optical paths and locations within a common projection system that are configured to output light into the associated ones of the waveguides 270, 280, 290, 300, 310. In some embodiments, the waveguides of the waveguide assembly 260 can function as ideal lenses while relaying the light input into the waveguides to the user's eye. In this concept, the object can be the spatial light modulator 540 and the image can be an image on a depth plane.

[0069] In some embodiments, the display system 250 may be a scanning fiber display comprising one or more scanning fibers configured to project light in various patterns (e.g., raster scan, spiral scan, Lissajous pattern, etc.) into one or more waveguides 270, 280, 290, 300, 310 and ultimately into the viewer's eye 210. In some embodiments, the illustrated image input devices 360, 370, 380, 390, 400 may schematically represent a single scanning fiber or a bundle of scanning fibers configured to input light into one or more waveguides 270, 280, 290, 300, 310. In some other embodiments, the illustrated image input devices 360, 370, 380, 390, 400 may schematically represent a plurality of scanning fibers or a plurality of bundles of scanning fibers, each configured to input light into the associated one of the waveguides 270, 280, 290, 300, 310. It should be understood that one or more optical fibers may be configured to transmit light from the optical module 530 to one or more waveguides 270, 280, 290, 300, 310. It should be understood that one or more intervening optical structures are provided between the scanning fiber or fibers and the one or more waveguides 270, 280, 290, 300, 310 and may, for example, redirect light exiting the scanning fiber into one or more of the waveguides 270, 280, 290, 300, 310.

[0070] Controller 560 controls the operation of one or more of the stacked waveguide assemblies 260, including the operation of the image input devices 360, 370, 380, 390, 400, the light source 530, and the light modulator 540. In some embodiments, controller 560 is part of the local data processing module 140. Controller 560 includes programming (e.g., instructions in a non-transitory medium) that adjusts the timing and provision of image information to waveguides 270, 280, 290, 300, 310, for example, according to any of the various schemes disclosed herein. In some embodiments, the controller may be a single integrated device or a distributed system connected by a wired or wireless communication channel. Controller 560 may, in some embodiments, also be part of processing module 140 or 150 (FIG. 9D).

[0071] Continuing to refer to FIG. 6, the waveguides 270, 280, 290, 300, 310 may be configured to propagate light within each individual waveguide by total internal reflection (TIR). The waveguides 270, 280, 290, 300, 310 may each be planar, or have another shape (e.g., curved), with major top and bottom surfaces and an edge extending between those major top and bottom surfaces. In the illustrated configuration, the waveguides 270, 280, 290, 300, 310 each include external coupling optical elements 570, 580, 590, 600, 610 configured to extract light from the waveguide by redirecting the light propagating within each individual waveguide out of the waveguide and outputting the image information to the eye 210. The extracted light may also be referred to as external coupled light, and the external coupling optical elements may also be referred to as light extraction optical elements. The beam of the extracted light may be output by the waveguide at the location where the light propagating within the waveguide impinges on the light extraction optical element. The external coupling optical elements 570, 580, 590, 600, 610 may be gratings, for example, including diffractive optical features as further discussed herein. For ease of explanation and clarity of the drawings, the external coupling optical elements 570, 580, 590, 600, 610 are shown disposed on the bottom major surfaces of the waveguides 270, 280, 290, 300, 310, but in some embodiments, the external coupling optical elements 570, 580, 590, 600, 610 may be disposed on the top and / or bottom major surfaces and / or directly within the volume of the waveguides 270, 280, 290, 300, 310, as further discussed herein. In some embodiments, the external coupling optical elements 570, 580, 590, 600, 610 may be attached to a transparent substrate and formed within a layer of material forming the waveguides 270, 280, 290, 300, 310. In some other embodiments, the waveguides 270, 280, 290, 300, 310 may be a monolithic piece of material, and the external coupling optical elements 570, 580, 590, 600, 610 may be formed on and / or within the surface of that piece of material.

[0072] Continuing to refer to FIG. 6, as discussed herein, each of the waveguides 270, 280, 290, 300, 310 is configured to output light and form an image corresponding to a particular depth plane. For example, the waveguide 270 closest to the eye may be configured to deliver collimated light (input into such a 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 deliver 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 generate a slight convex wavefront curvature such that the eye / brain interprets the light originating from the next upper waveguide 280 as originating from a first focal plane that is closer inwardly from the optically infinite towards the eye 210. Similarly, the third upper waveguide 290 passes its output light through both the first lens 350 and the second lens 340 before reaching the eye 210. The combined refractive power of the first lens 350 and the second lens 340 may be configured to generate another incremental amount of wavefront curvature such that the eye / brain interprets the light originating from the third upper waveguide 290 as originating from a second focal plane that is even closer inwardly from the optically infinite towards the person than the light from the next upper waveguide 280 was interpreted as originating from.

[0073] The other waveguide layers 300, 310 and lenses 330, 320 are similarly configured, and the top waveguide 310 in the stack sends its output through all of the lenses between it and the eye for the collective focusing power that represents the focal plane closest to the person. When viewing / interpreting light originating from the world 510 on the other side of the stacked waveguide assembly 260, a compensating lens layer 620 may be disposed on top of the stack to compensate for the stack of lenses 320, 330, 340, 350. Such a configuration provides the same number of perceived focal planes as there are available waveguide / lens pairs. Both the external coupling optical elements of the waveguides and the focusing sides of the lenses may be static (i.e., not dynamic or electroactive). In some alternative embodiments, one or both may be dynamic using electroactive features.

[0074] In some embodiments, two or more of the waveguides 270, 280, 290, 300, 310 may have the same associated depth plane. For example, a plurality of waveguides 270, 280, 290, 300, 310 may be configured to output images set to the same depth plane, or a plurality of subsets of the waveguides 270, 280, 290, 300, 310 may be configured to output images set to the same plurality of depth planes, using one set per depth plane. This can provide an advantage for forming tiled images to provide an expanded field of view at those depth planes.

[0075] Continuing to refer to FIG. 6, the external coupling optical elements 570, 580, 590, 600, 610 may be configured to redirect light out of their respective waveguides for a particular depth plane associated with the waveguide and output the light with an appropriate amount of divergence or collimation. As a result, the waveguides having different associated depth planes may have different configurations of the external coupling optical elements 570, 580, 590, 600, 610 that 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 may be three-dimensional or surface features configured to output light at a specific angle. For example, the light extraction optical elements 570, 580, 590, 600, 610 may be a volume hologram, a surface hologram, and / or a diffraction grating. In some embodiments, the features 320, 330, 340, 350 may not be lenses. Rather, they may simply be spacers (e.g., a cladding layer and / or structure for forming a void).

[0076] In some embodiments, the external coupling optical elements 570, 580, 590, 600, 610 are diffraction features or “diffractive optical elements” (also referred to herein as “DOEs”) that form a diffraction pattern. Preferably, the DOE has a sufficiently low diffraction efficiency such that only a portion of the light of the beam is deflected towards the eye 210 at each intersection of the DOE, while the remainder continues to travel through the waveguide via TIR. The light carrying the image information is thus split into several associated output beams that exit the waveguide at multiple locations, resulting in a very uniform pattern of output emission towards the eye 210 with respect to this particular collimated beam that bounces within the waveguide.

[0077] In some embodiments, one or more DOEs may be switchable 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 may comprise a layer of polymer dispersed liquid crystal in which microdroplets have a diffraction pattern within a host medium, and the refractive index of the microdroplets may be switched to substantially match that of the host material (in which case the pattern does not significantly diffract the incident light), or the microdroplets may be switched to a refractive index that does not match that of the host medium (in which case the pattern actively diffracts the incident light).

[0078] In some embodiments, a camera assembly 630 (e.g., a digital camera including visible and infrared light cameras) may be provided to capture an image of the eye 210 and / or the tissue surrounding the eye 210, e.g., to detect user input and / or monitor the physiological state of the user. As used herein, a camera may be any image capture device. In some embodiments, the camera assembly 630 may include an image capture device and a light source (e.g., infrared light) that projects light onto the eye and is then reflected by the eye and detected by the image capture device. In some embodiments, the camera assembly 630 may be attached to the frame 80 (FIG. 9D) and may communicate electrically with a processing module 140 and / or 150 that can process image information from the camera assembly 630. In some embodiments, one camera assembly 630 may be utilized per eye to monitor each eye separately.

[0079] Referring now to FIG. 7, an embodiment of an output beam output by a waveguide is shown. Although one waveguide is illustrated, it should be understood that other waveguides within the waveguide assembly 260 (FIG. 6) may function similarly, and the waveguide assembly 260 includes a plurality of waveguides. Light 640 is input into the waveguide 270 at the input surface 460 of the waveguide 270 and propagates within the waveguide 270 by TIR. At the point where the light 640 impinges on the DOE 570, a portion of the light exits the waveguide as the output beam 650. The output beams 650 are illustrated as being substantially parallel, but as discussed herein, they may also be redirected at an angle to propagate to the eye 210 depending on the depth plane associated with the waveguide 270 (e.g., to form a diverging output beam). It should be understood that a waveguide with an external coupling optical element that externally couples light to form an image that appears to be set on a depth plane at a long distance (e.g., optical infinity) from the eye 210 may be shown for the substantially parallel output beams. Other waveguides or other sets of external coupling optical elements may output a more divergent output beam pattern, which would require the eye 210 to focus at a closer distance and would be interpreted by the brain as light from a distance closer to the eye 210 than optical infinity.

[0080] In some embodiments, a full-color image may be formed on each depth plane by overlaying the image on each of the primary colors, e.g., three or more primary colors. FIG. 8 illustrates an example of a stacked waveguide assembly in which each depth plane includes an image formed using a plurality of different primary 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 primary 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. Different depth planes are shown in the figure by different numbers associated with diopters (dpt) following the letters G, R, and B. As a mere example, the numbers following each of these letters indicate the diopter (1 / m), i.e., the inverse distance of the depth plane from the viewer, and each box in the figure represents an individual primary color image. In some embodiments, the exact placement of the depth planes for different primary colors may vary to account for differences in the focusing of light of different wavelengths by the eye. For example, the different primary color images for a given depth plane may be placed on depth planes corresponding to different distances from the user. Such an arrangement may increase visual acuity and user comfort and / or reduce chromatic aberration.

[0081] In some embodiments, the light of each primary color may be output by a single dedicated waveguide, and as a result, each depth plane may have a plurality of waveguides associated therewith. In such embodiments, it can be understood that each box in the figure, including those containing the letters G, R, or B, represents an individual waveguide, and three waveguides may be provided for each depth plane where three primary color images are provided for each depth plane. The waveguides associated with each depth plane are shown adjacent to each other in this figure for ease of explanation, but it should be understood that in a physical device, all of the waveguides may be arranged in a stack with one waveguide per level. In some other embodiments, a plurality of primary colors may be output by the same waveguide such that, for example, only a single waveguide is provided for each depth plane.

[0082] Continuing to refer to FIG. 8, in some embodiments, G is green, R is red, and B is blue. In some other embodiments, other colors associated with other wavelengths of light, including magenta and cyan, may also be used in addition to or in place of one or more of red, green, or blue.

[0083] It should be understood that references throughout this disclosure to the color of a given light are understood to encompass light of one or more wavelengths within the range of wavelengths of light that are perceived by a viewer as being that given color. For example, red light may include light of one or more wavelengths within the range of approximately 620 - 780 nm, green light may include light of one or more wavelengths within the range of approximately 492 - 577 nm, and blue light may include light of one or more wavelengths within the range of approximately 435 - 493 nm.

[0084] In some embodiments, the light source 530 (FIG. 6) may be configured to emit light of one or more wavelengths outside of the viewer's visual perception range, such as infrared and / or ultraviolet wavelength light. Additionally, the internal coupling, external coupling, and other light redirection structures of the waveguide of the display 250 may be configured to direct and emit this light from the display towards the user's eye 210, for example, for imaging and / or user stimulation applications.

[0085] Referring now to FIG. 9A, in some embodiments, light that impinges on the waveguide may need to be redirected to internally couple that light into the waveguide. An internal coupling optical element may be used to redirect and internally couple the light into its corresponding waveguide. FIG. 9A illustrates a cross-sectional side view of an example of a stack of a plurality or set 660 of waveguides, each including an internal coupling optical element. Each waveguide may be configured to output light of one or more different wavelengths or one or more different wavelength ranges. Stack 660 may correspond to stack 260 (FIG. 6), and it should be understood that the illustrated waveguides of stack 660 may correspond to a portion of the plurality of waveguides 270, 280, 290, 300, 310, except that light from one or more of the image input devices 360, 370, 380, 390, 400 is input into the waveguide from a position that requires the light to be redirected for internal coupling.

[0086] The illustrated set 660 of stacked waveguides includes waveguides 670, 680, and 690. Each waveguide includes an associated internal coupling optical element (which may also be referred to as a light input area on the waveguide). For example, internal coupling optical element 700 is disposed on a major surface (e.g., the upper major surface) of waveguide 670, internal coupling optical element 710 is disposed on a major surface (e.g., the upper major surface) of waveguide 680, and internal coupling optical element 720 is disposed on a major surface (e.g., the upper major surface) of waveguide 690. In some embodiments, one or more of the internal coupling optical elements 700, 710, 720 may be disposed on the bottom major surface of the respective waveguides 670, 680, 690 (particularly, when one or more of the internal coupling optical elements are reflective deflecting optical elements). As illustrated, the internal coupling optical elements 700, 710, 720 may be disposed on the upper major surface (or the upper portion of the next lower waveguide) of their respective waveguides 670, 680, 690, particularly when those internal coupling optical elements are transmissive deflecting optical elements. In some embodiments, the internal coupling optical elements 700, 710, 720 may be disposed within the bodies of the respective waveguides 670, 680, 690. In some embodiments, as discussed herein, the internal coupling optical elements 700, 710, 720 are wavelength selective so as to selectively redirect one or more wavelengths of light while transmitting other wavelengths of light. Although illustrated on one side or corner of their respective waveguides 670, 680, 690, it should be understood that the internal coupling optical elements 700, 710, 720 may be disposed within other areas of their respective waveguides 670, 680, 690 in some embodiments.

[0087] As shown, the internally coupled optical elements 700, 710, 720 may be laterally offset from each other. In some embodiments, each internally coupled optical element may be offset such that its light is received without passing through another internally coupled optical element. For example, each of the internally coupled optical elements 700, 710, 720 may be configured to receive light from different image input devices 360, 370, 380, 390, and 400, as shown in FIG. 6, and may be separated (e.g., laterally spaced) from other internally coupled optical elements 700, 710, 720 such that it receives substantially no light from other ones of the internally coupled optical elements 700, 710, 720.

[0088] Each waveguide also includes an associated light dispersing element. For example, the light dispersing element 730 is disposed on a major surface (e.g., upper major surface) of the waveguide 670, the light dispersing element 740 is disposed on a major surface (e.g., upper major surface) of the waveguide 680, and the light dispersing element 750 is disposed on a major surface (e.g., upper major surface) of the waveguide 690. In some other embodiments, the light dispersing elements 730, 740, 750 may each be disposed on a bottom major surface of the associated waveguides 670, 680, 690. In some other embodiments, the light dispersing elements 730, 740, 750 may each be disposed on both the upper and bottom major surfaces of the associated waveguides 670, 680, 690, or the light dispersing elements 730, 740, 750 may each be disposed on different ones of the upper and bottom major surfaces within different associated waveguides 670, 680, 690.

[0089] Waveguides 670, 680, 690 may be separated and isolated, for example, by a gas, liquid, and / or solid layer of material. For example, as shown, 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 from a low refractive index material (i.e., a material having a lower refractive index than the material forming the directly adjacent ones of waveguides 670, 680, 690). Preferably, the refractive index of the material forming layers 760a, 760b is 0.05 or more, or 0.10 or less than the refractive index of the material forming waveguides 670, 680, 690. Advantageously, the lower refractive index layers 760a, 760b may function as cladding layers that facilitate total internal reflection (TIR) of light (e.g., TIR between the upper and bottom major surfaces of each waveguide) through waveguides 670, 680, 690. In some embodiments, layers 760a, 760b are formed from air. It should be understood that although not shown, the top and bottom of the illustrated set 660 of waveguides may include the nearest cladding layer.

[0090] Preferably, for ease of manufacturing and other considerations, the materials forming waveguides 670, 680, 690 are similar or identical, and the materials forming layers 760a, 760b are similar or identical. 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 still be different while maintaining the various refractive index relationships described above.

[0091] Continuing to refer to FIG. 9A, light rays 770, 780, 790 are incident on the set 660 of waveguides. It should be understood that light rays 770, 780, 790 may be input into waveguides 670, 680, 690 by one or more image input devices 360, 370, 380, 390, 400 (FIG. 6).

[0092] In some embodiments, the light rays 770, 780, 790 may have different properties, such as different wavelengths or different wavelength ranges, corresponding to different colors. The internal coupling optical elements 700, 710, 720 each deflect the incident light so that light propagates through an individual one of the waveguides 670, 680, 690 by TIR. In some embodiments, the internal coupling optical elements 700, 710, 720 each selectively deflect one or more specific wavelengths of light while transmitting other wavelengths to the underlying waveguide and the associated internal coupling optical element.

[0093] For example, the internal coupling optical element 700 may be configured to selectively deflect the light ray 770 having the first wavelength or wavelength range while transmitting the light rays 780 and 790 having different second and third wavelengths or wavelength ranges, respectively. The transmitted light ray 780 impinges on the internal coupling optical element 710 configured to deflect light having the second wavelength or wavelength range and is thereby deflected. The light ray 790 is deflected by the internal coupling optical element 720 configured to selectively deflect light having the third wavelength or wavelength range.

[0094] Continuing to refer to FIG. 9A, the deflected light rays 770, 780, 790 are deflected to propagate through the corresponding waveguides 670, 680, 690. That is, the internal coupling optical elements 700, 710, 720 of each waveguide deflect light into its corresponding waveguide 670, 680, 690 and internally couple the light into the corresponding waveguide. The light rays 770, 780, 790 are deflected at an angle that causes the light to propagate through the individual waveguides 670, 680, 690 by TIR. The light rays 770, 780, 790 propagate through the individual waveguides 670, 680, 690 by TIR until they impinge on the corresponding light dispersion elements 730, 740, 750 of the waveguide.

[0095] Referring now to FIG. 9B, a perspective view of an embodiment of the plurality of stacked waveguides of FIG. 9A is illustrated. As described above, the internally coupled light rays 770, 780, 790 are each deflected by the internally coupled optical elements 700, 710, 720 and then propagate by TIR within waveguides 670, 680, 690, respectively. The light rays 770, 780, 790 then each impinge on the light dispersing elements 730, 740, 750. The light dispersing elements 730, 740, 750 deflect the light rays 770, 780, 790 so as to propagate towards the external coupling optical elements 800, 810, 820, respectively.

[0096] In some embodiments, the optical dispersion elements 730, 740, 750 are orthogonal pupil expanders (OPEs). In some embodiments, the OPE deflects or disperses light to the external coupling optical elements 800, 810, 820, and in some embodiments, also increases the beam or spot size of the present light as it propagates to the external coupling optical elements. In some embodiments, the optical dispersion elements 730, 740, 750 may be omitted, and the internal coupling optical elements 700, 710, 720 may be configured to directly deflect light to the external coupling optical elements 800, 810, 820. For example, referring to FIG. 9A, the optical dispersion elements 730, 740, 750 may each be replaced with the external coupling optical elements 800, 810, 820. In some embodiments, the external coupling optical elements 800, 810, 820 are an exit pupil (EP) or an exit pupil expander (EPE) that directs light within the viewer's eye 210 (FIG. 7). It should be understood that the OPE may be configured to increase the size of the eyebox in at least one axis, and the EPE may increase the eyebox in an axis that intersects, for example, is orthogonal to, the axis of the OPE. For example, each OPE may be configured to redirect a portion of the light impinging on the OPE to the EPE of the same waveguide while allowing the remaining portion of the light to continue to propagate along the waveguide. Again, in response to a collision with the OPE, another portion of the remaining light is redirected to the EPE, and the remaining portion of that portion continues to propagate further along the waveguide or the like. Similarly, in response to a collision with the EPE, a portion of the colliding light is directed out of the waveguide towards the user, and the remaining portion of that light continues to propagate through the waveguide until it impinges on the EP again, at which point another portion of the colliding light is directed out of the waveguide, and so on. As a result, a single beam of internally coupled light is "replicated" each time a portion of that light is redirected by the OPE or EPE, thereby forming a beam field of cloned light as shown in FIG. 6. In some embodiments, the OPE and / or EPE may be configured to modify the size of the beam of light.

[0097] Thus, referring to FIGS. 9A and 9B, in some embodiments, the waveguide set 660 includes, for each primary color, waveguides 670, 680, 690, internal coupling optical elements 700, 710, 720, light dispersion elements (e.g., OPE) 730, 740, 750, and external coupling optical elements (e.g., EP) 800, 810, 820. The waveguides 670, 680, 690 may be stacked with a gap / cladding layer between each one. The internal coupling optical elements 700, 710, 720 redirect or deflect the incident light into their respective waveguides (using different internal coupling optical elements that receive light of different wavelengths). The light then propagates at an angle that will result in TIR within the individual waveguides 670, 680, 690. In the illustrated example, the ray 770 (e.g., blue light) is polarized by the first internal coupling optical element 700 in the manner described above, then bounces along the waveguide and interacts with the light dispersion element (e.g., OPE) 730, then the external coupling optical element (e.g., EP) 800. The rays 780 and 790 (e.g., green and red light, respectively) pass through the waveguide 670, and the ray 780 collides with the internal coupling optical element 710 and is thereby deflected. The ray 780 then bounces along the waveguide 680 via TIR and proceeds to its light dispersion element (e.g., OPE) 740, then the external coupling optical element (e.g., EP) 810. Finally, the ray 790 (e.g., red light) passes through the waveguide 690 and collides with the internal coupling optical element 720 of the waveguide 690. The internal coupling optical element 720 deflects the ray 790 such that the ray propagates by TIR to the light dispersion element (e.g., OPE) 750, then by TIR to the external coupling optical element (e.g., EP) 820. The external coupling optical element 820 then finally externally couples the ray 790 to the viewer, who also receives the light externally coupled from the other waveguides 670, 680.

[0098] FIG. 9C illustrates a top and bottom plan view of an embodiment of a plurality of stacked waveguides of FIGS. 9A and 9B. As shown, waveguides 670, 680, 690 may be vertically aligned with associated optical dispersion elements 730, 740, 750 and associated external coupling optical elements 800, 810, 820 of each waveguide. However, as discussed herein, internal coupling optical elements 700, 710, 720 are not vertically aligned. Rather, the internal coupling optical elements are preferably non-overlapping (e.g., laterally spaced as seen in the top and bottom views). As further discussed herein, this non-overlapping spatial arrangement facilitates the injection of light from different resources into different waveguides on a one-to-one basis, thereby enabling a specific light source to be uniquely coupled to a specific waveguide. In some embodiments, an array including non-overlapping spatially separated internal coupling optical elements may be referred to as an offset pupil system, and the internal coupling optical elements within these arrays may correspond to sub-pupils.

[0099] FIG. 9D illustrates an embodiment of a wearable display system 60 in which various waveguides and related systems disclosed herein may be integrated. In some embodiments, display system 60 is the system 250 of FIG. 6, which schematically shows some parts of that system 60 in more detail. For example, the waveguide assembly 260 of FIG. 6 may be part of display 70.

[0100] Continuing to refer to FIG. 9D, the display system 60 includes a display 70 and various mechanical and electronic modules and systems for supporting the functions of the display 70. The display 70 can be worn by a display system user or viewer 90 and may be coupled to a frame 80 configured to position the display 70 in front of the user 90's eyes. In some embodiments, the display 70 can be regarded as an eyepiece. In some embodiments, a speaker 100 is coupled to the frame 80 and configured to be positioned adjacent to the user 90's outer ear canal (in some embodiments, another speaker, not shown, can optionally be positioned adjacent to the other outer ear canal of the user to provide stereo / formable sound control). The display system 60 also includes one or more microphones 110 or other devices that may detect sound. In some embodiments, the microphone is configured to enable the user to provide an input or command (e.g., selection of a voice menu command, natural language question, etc.) to the system 60 and / or to enable audio communication with other persons (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., sound from the user and / or the environment). In some embodiments, the display system also includes a peripheral sensor 120a that is separate from the frame 80 and can be attached to the user 90's body (e.g., on the user 90's head, torso, limbs, etc.). In some embodiments, the peripheral sensor 120a may be configured to obtain data for characterizing the physiological state of the user 90. For example, the sensor 120a may be an electrode.

[0101] Continuing to refer to FIG. 9D, display 70 is operatively coupled to local data processing module 140 by a communication link 130, such as a wired conductor or wireless connectivity, which may be mounted in various configurations, such as fixedly attached to frame 80, fixedly attached to a helmet or hat worn by a user, built into headphones, or removably attached to user 90 in some other manner (e.g., in a backpack configuration, in a belt attachment configuration). Similarly, sensor 120a may be operatively coupled to local processor and data module 140 by a communication link 120b, such as a wired conductor or wireless connectivity. Local processing and data module 140 may include digital memory, such as a hardware processor and non-volatile memory (e.g., flash memory or hard disk drive), both of which may be utilized to assist in the processing, caching, and storage of data. Optionally, local processor and data module 140 may include one or more central processing units (CPUs), graphics processing units (GPUs), dedicated processing hardware, etc. Data may include (a) data captured from sensors such as (e.g., operatively coupled to frame 80 or otherwise attachable to user 90) image capture devices (such as cameras), microphones, inertial measurement units, accelerometers, compasses, GPS units, wireless devices, gyroscopes, and / or other sensors disclosed herein, and / or (b) optionally, data obtained and / or processed using remote processing module 150 and / or remote data repository 160 (including data related to virtual content) for passage to display 70 after processing or retrieval. Local processing and data module 140 may be operatively coupled to remote processing module 150 and remote data repository 160 by communication links 170, 180, such as via a wired or wireless communication link, such that these remote modules 150, 160 are operatively coupled to each other and available as resources to local processing and data module 140.In some embodiments, the local processing and data module 140 may include one or more of an image capture device, a microphone, an inertial measurement unit, an accelerometer, a compass, a GPS unit, a wireless device, and / or a gyroscope. In some other embodiments, one or more of these sensors may be attached to the frame 80 or may be a stand-alone structure that communicates with the local processing and data module 140 via a wired or wireless communication path.

[0102] Continuing to refer to FIG. 9D, in some embodiments, the remote processing module 150 may include one or more processors configured to analyze and process data and / or image information, including, for example, one or more central processing units (CPUs), a graphics processing unit (GPU), dedicated processing hardware, etc. In some embodiments, the remote data repository 160 may include a digital data storage facility, which may be available through the Internet or other networking configurations in a “cloud” resource configuration. In some embodiments, the remote data repository 160 may include one or more remote servers that provide information, such as information for generating augmented reality content, to the local processing and data module 140 and / or the remote processing module 150. In some embodiments, all data is stored and all calculations are performed in the local processing and data module, enabling complete autonomous use from the remote module. Optionally, an external system (e.g., one or more processors, a system of one or more computers) including a CPU, GPU, etc. may perform at least a portion of the processing (e.g., generating image information, processing data) and provide information to and receive information from modules 140, 150, 160, for example, via a wireless or wired connection. (Waveguide integrated with an optical element having a blazed grating)

[0103] Providing an immersive experience to a user of a waveguide-based display system, such as various translucent or transparent display systems configured for virtual / augmented / mixed reality display applications as described above, depends, inter alia, on various characteristics of optical coupling into and out of the waveguide of the display system. For example, a virtual / augmented / mixed reality display having high internal and external coupling efficiency for one or more polarizations of light can improve the viewing experience by providing relatively high brightness and / or clarity.

[0104] For example, as described above with reference to FIGS. 6 and 7, a display system according to various embodiments described herein may include optical elements, such as internal coupling optical elements, external coupling optical elements, and / or light dispersing elements, which may in turn comprise diffraction gratings or diffractive optical elements (DOEs). An internal coupling optical element, such as an internal coupling diffraction grating (ICG), may be employed to couple light into the waveguide, and an external coupling optical element, such as an exit pupil expander (EPE), may be employed to couple light out of the waveguide and into the user's eye. For example, as described above with reference to FIGS. 6 and 7, light 640 incident into waveguide 270 at input surface 460 of waveguide 270 propagates within waveguide 270 by total internal reflection (TIR). At the point where light 640 impinges on external coupling optical element 570, a portion of the light exits the waveguide as beamlet 650. In some implementations, any of optical elements 570, 580, 590, 600, 610 can include or be configured as a diffraction grating or DOE.

[0105] To achieve the desirable characteristics of internal coupling (or external coupling therefrom) of light into the waveguides 270, 280, 290, 300, 310, the optical elements 570, 580, 590, 600, 610 configured as diffraction gratings or DOEs are formed from suitable materials for controlling various optical properties including diffractive properties and can have a suitable structure. Desirable diffractive properties include, among others, spectral selectivity, angular selectivity, polarization selectivity, high spectral bandwidth, wide field of view, and high diffraction efficiency.

[0106] To achieve one or more of these and other advantages, including a relatively high diffraction efficiency of the optical element, the various exemplary optical elements described herein include blazed diffraction gratings. A blazed diffraction grating is configured (e.g., optimized) to achieve an improved diffraction efficiency for a given diffraction order (e.g., the first order) such that the refractive power is improved or maximized for that given diffraction order while the residual refractive power at other orders (e.g., the zero order) is reduced or minimized. For example, the blazed diffraction grating pattern has a geometry configured to have a first order diffraction efficiency greater than 30%, 40%, 50%, 60%, or 70% for at least one polarization of light. Such a configuration or optimization of the grating occurs with respect to a particular wavelength, referred to as the blaze wavelength, for which the blazed diffraction grating is designed, configured, and / or optimized.

[0107] Improved diffraction efficiency for a given diffraction order is achieved in some blazed diffraction gratings by having faceted features, such as faceted lines. A blazed diffraction grating having faceted lines can be fabricated by imprinting a blazed diffraction grating pattern onto a device substrate, such as a waveguide, using a device master template as an imprint mold. In such a fabrication process, the manufacturing throughput can be limited by the number of blazed diffraction grating patterns that the device master template can imprint onto a given device substrate. Advantageously, in the manufacturing techniques described herein, the device master template is configured to imprint a relatively large number of blazed diffraction grating patterns onto the device substrate, thereby enabling a relatively high manufacturing throughput of blazed diffraction gratings. In particular, in the disclosed techniques, a device master template having blazed diffraction grating patterns extending in a plurality of directions, such as radially, is fabricated, which enables efficient use of the area of the device master template for high-throughput parallel, such as simultaneous, imprinting of blazed diffraction grating patterns onto a device substrate such as a waveguide.

[0108] FIG. 10A illustrates a cross-sectional view of an exemplary blazed transmissive diffraction grating 1008 that may be included as part of an optical element such as an internal coupling optical element and / or an external coupling optical element or both. The blazed diffraction grating 1008 has a constant pitch d. In operation, an incident light beam 1016 incident at an angle α with respect to the normal direction 1002 (e.g., the z-direction) is diffracted as a diffracted light beam 1024 at a blaze angle β with respect to the normal direction 1002 at a relatively high or maximum efficiency. A blazed diffraction grating such as the illustrated blazed transmissive diffraction grating 1008 can be characterized by a blaze angle β, a blaze wavelength, and a diffraction order with respect to which the blazed diffraction grating is designed or optimized. Although a transmissive diffraction grating 1008 is shown, in other configurations, the diffraction grating can serve as a reflective diffraction grating that diffracts light reflected therefrom and couples, for example, the light into a waveguide for guiding therein by total internal reflection or out of the waveguide and / or performs other functions.

[0109] A blazed diffraction grating such as the illustrated blazed transmissive diffraction grating 1008 can have, for example, a triangular cross-sectional shape, a sawtooth shape, or lattice features (e.g., lines). For example, in the illustrated embodiment, the cross-sectional shape has a triangular sawtooth shape that forms an inclined stepped structure. The steps can be inclined at a facet angle δ, also referred to as a blaze angle, with respect to a horizontal plane, e.g., the x-y plane normal to the lattice normal direction 1002 (e.g., the z-direction).

[0110] In some implementations, the blazed transmissive diffraction grating 1008 can have a particular arrangement known as a Littrow configuration in which the diffraction angle β, the incident angle α, and the facet angle δ are the same. Thus, in the Littrow configuration, α = β = δ.

[0111] The blaze angle δ can be designed or optimized to improve or maximize the efficiency of light having a particular wavelength. As described above, a blazed transmissive diffraction grating according to an embodiment diffracts visible light incident thereon into individual waveguides such that the visible light diffracted into the waveguides is guided within each of the waveguides, for example, by total internal reflection (TIR). In some implementations, the diffraction grating can be configured to diffract visible light into individual waveguides when the visible light is incident thereon within a range of individual angles or fields of view (FOV). In some other implementations, the diffraction grating can also be configured to diffract visible light out of individual waveguides into a range of individual angles or fields of view. In some other implementations, the diffraction grating can be configured as a light dispersing element that disperses light and propagates it within the waveguide towards an external coupling element. In yet some other implementations, the diffraction grating can serve as a combined external coupling grating and light dispersing element that disperses light and is configured to propagate within the waveguide and further configured to externally couple the light out of the waveguide.

[0112] In the embodiment illustrated in FIG. 10A, the diffraction grating 1008 includes a plurality of blazed diffraction grating lines 1012 that extend in a first horizontal or y-direction and are periodically repeated in a second horizontal or x-direction. The diffraction grating lines 1012 can be, for example, straight and continuous lines that extend in the y-direction. However, embodiments are not so limited.

[0113] In some implementations, the diffraction grating lines 1012 can be, for example, discontinuous lines in the y-direction. In some other implementations, the discontinuous lines can form a plurality of pillars that protrude from the surface of the grating substrate. In some implementations, at least some of the diffraction grating lines 1012 can have different widths in the x-direction.

[0114] In the illustrated embodiment, the diffraction grating lines 1012 have a sawtooth profile with asymmetric opposing side surfaces that form different angles with respect to a profile, e.g., the plane of the substrate. However, the embodiments are not so limited and in other implementations, the diffraction grating lines 1012 can have symmetric opposing side surfaces that form similar angles with respect to the plane of the substrate.

[0115] In the illustrated embodiment, the diffraction grating lines 1012 are arranged as a one-dimensional (1D) array having periodicity in one lateral direction, e.g., the x-direction. In these configurations, the 1D array can serve as a 1D grating configured to preferentially diffract light in one direction. However, the embodiments are not so limited and in other configurations, the diffraction grating lines 1012, e.g., discontinuous lines or protrusions, can be arranged as a two-dimensional (2D) array having periodicity in two lateral directions. In these configurations, the 2D array serves as a 2D grating configured to preferentially diffract light in two directions. In certain implementations, the 2D array can have the same number of diffraction features in two different lateral directions and form, e.g., a square array.

[0116] FIG. 10B illustrates a partial cross-sectional view of a display device 1000 that includes a waveguide 1004 and a blazed transmissive diffraction grating 1008 formed on the waveguide 1004, according to some embodiments. The blazed transmissive diffraction grating 1008 is configured to diffract light having wavelengths within the visible spectrum such that the light is guided within the waveguide 1004 by TIR. The waveguide 1004 may correspond to, for example, one of the waveguides 670, 680, 690 described above with respect to FIGS. 9A-9C. As described above, the blazed transmissive diffraction grating 1008 may correspond to, for example, an internal coupling optical element (700, 710, 720, FIGS. 9A-9C), also referred to herein as an internal coupling grating (ICG). The display device 1000 may additionally include various other optical elements, including external coupling optical elements, as part of the display device described above. For example, in the illustrated embodiment, the display device 1000 additionally includes light dispersing elements 730, 740, 750 similar to those described above with respect to FIGS. 9A-9C. The display device 1000 may include other elements, such as, for example, external coupling optical elements (800, 810, 820, FIGS. 9A-9C).

[0117] During operation, when an incident light beam 1016, e.g., visible light, is incident on the blazed diffraction grating 1008 at an incident angle α measured with respect to the surface normal 1002 that is normal or orthogonal to the surface 1008S extending in the y-x plane, the blazed diffraction grating 1008 at least partially diffracts the incident light beam 1016 as a diffracted light beam 1024 at a diffraction angle θ measured with respect to the surface normal 1002 while at least partially transmitting the incident light as a transmitted light beam 1020. The diffracted light beam 1024 is at a critical angle θ for the occurrence of total internal reflection within the waveguide 1004 TIRWhen diffracted at a diffraction angle θ exceeding this value, the diffracted light beam 1024 is guided within the waveguide 1004 along the x-axis via total internal reflection (TIR) until the diffracted light beam 1024 reaches one of, for example, the optical dispersion elements 730, 740, 750, or one of, for example, the external coupling optical elements (800, 810, 820, FIGS. 9A - 9C). (Fabrication of Blazed Grating Structures Using a Master Template)

[0118] In some fabrication techniques, the blazed diffraction grating is fabricated by directly imprinting the blazed diffraction grating pattern onto a substrate, such as a device substrate like a waveguide. In some other fabrication techniques, the blazed diffraction grating is fabricated by imprinting a patterned layer, which is then used to pattern the blazed diffraction grating pattern into the substrate. In these techniques, the imprint process can utilize a master template. The master template can have a blazed diffraction grating structure similar and corresponding to the final blazed diffraction grating pattern, such as the pattern of the blazed transmissive diffraction grating l008 illustrated in FIG. 10A. Thus, in various embodiments, the blazed diffraction grating pattern can serve as a master template for fabricating the final blazed diffraction grating. For example, a blazed diffraction grating structure such as the blazed diffraction grating 1008 illustrated in FIG. 10A can serve as a master template for imprinting a photoresist pattern that can be used as a blazed diffraction grating pattern or a patterned layer that is used as a partial mask for etching the blazed diffraction grating pattern into the substrate directly below it.

[0119] In yet other fabrication techniques, the blazed diffraction grating structure can also serve as a master template for fabricating another master template. For example, a blazed diffraction grating structure such as the blazed transmissive diffraction grating 1008 illustrated in FIG. 10A can serve as a master template for imprinting a photoresist pattern that includes a blazed diffraction grating pattern or a patterned layer for patterning the blazed diffraction grating pattern into the substrate directly below, and the resulting substrate having the blazed diffraction grating pattern formed thereon can, in turn, be used as a master template for forming another master template for fabricating the final blazed diffraction grating.

[0120] As described herein, a first master template that is used to imprint a structure that is used to fabricate another master template is referred to as a primary master template. As described herein, a final master template that is used to imprint a structure onto a device substrate, e.g., a waveguide, is referred to as a device master template. There may be additional master templates involved in forming the blazed diffraction grating on the device substrate. When more than two master templates, including the primary master template and the device master template, are used to fabricate the ultimately imprinted structure of the device, the intervening master templates may be referred to herein as intermediate master templates, e.g., the nth intermediate master template, where n = 1, 2, etc.

[0121] Various process flows for processing a display device having an optical element such as an integrated blazed diffraction grating thereon may utilize manufacturing platforms, substrates, and tools used in or similar to those used in semiconductor or display device processing. For example, some master templates for imprinting a blazed diffraction grating structure may be formed on a semiconductor substrate such as a silicon wafer. A semiconductor wafer such as a silicon wafer has naturally occurring crystallographic planes that lead to the formation of facets arranged at a specific angle, as illustrated in the blazed transmissive diffraction grating 1008 of FIG. 10A. Thus, it can be advantageous for forming a master template, such as a primary master template, having a blazed diffraction grating structure such as the sawtooth blazed diffraction grating structure described above with respect to FIG. 10A. For example, as will be described in detail below, a silicon wafer contains different crystallographic planes that have different wet etching rates when exposed to certain chemicals. The different etching rates of the different crystal planes of silicon can advantageously be used to form a blazed diffraction grating pattern having facets such as those illustrated with respect to the blazed transmissive diffraction grating 1008 shown in FIG. 10A. For example, wet etching a silicon wafer in certain chemicals such as potassium hydroxide (KOH) can naturally form pits, grooves, or lines having preferential crystalline facets, which can be adapted as a blazed diffraction grating pattern for a master template for processing a blazed diffraction grating, such as a primary master template.

[0122] Since the substrate such as a silicon wafer has a circular shape and the silicon crystal has a cubic crystal symmetry, when the blazed diffraction grating pattern is formed in the silicon using the preferential crystallinity facet as described above, the faceted lines on which the blazed diffraction grating pattern is formed can extend in a predetermined direction, for example, a direction predefined by a certain crystallographic direction. These directions can have a parallel or orthogonal or horizontal or vertical relationship due to a specific angular relationship therebetween, for example, due to the cubic symmetry and rhombohedral cubic crystal structure of crystalline silicon. However, forming a plurality of the same master templates each having a blazed diffraction grating pattern extending in these respective predetermined directions can result in a relatively inefficient use of the overall occupied area of the silicon wafer. This is illustrated with reference to FIG. 11A. FIG. 11A illustrates a top and bottom view of an exemplary master template 1100A which may include a master template substrate 1100 such as a {100}-oriented silicon wafer having a plurality of device template regions 1104 formed thereon. Each of the device template regions 1104 includes a blazed diffraction grating pattern region 1108. Each of the blazed diffraction grating pattern regions 1108 includes blazed diffraction grating lines extending in the x-direction or the y-direction, which can be, for example, the preferential direction of facet elongation within the silicon crystal, and thus in the same predetermined direction. When the lines of the blazed diffraction grating pattern region 1108 are restricted to extend in the same direction for different blazed diffraction grating pattern regions 1108 as shown, the use of the substrate occupied area in defining the device template regions 1104 can become less efficient than in an arrangement that allows the lines of the blazed diffraction grating pattern region 1108 to extend in different directions not limited to crystallographic directions, for example, in a substantially radial direction. An exemplary arrangement in which the device template regions 1104 have blazed diffraction grating lines of the blazed diffraction grating pattern regions 1108 extending in different directions is illustrated in the top and bottom view of an exemplary master template 1100B in FIG. 11B according to an embodiment.Similar to the master template 1100A, the illustrated master template 1100B includes a master template substrate 1100 having a plurality of device template regions 1104 formed thereon. Each of the device template regions 1104 includes a blazed diffraction grating pattern region 1108. However, unlike the device template regions 1104 of the master template 1100A illustrated in FIG. 11A where the lines of the different blazed diffraction grating pattern regions 1108 extend in the same direction, the blazed diffraction grating regions 1108 of the different device template regions 1104 extend in different directions not limited to crystallographic directions. In particular, the device template regions 1104 and the blazed diffraction grating pattern regions 1108 are defined in a radial (possibly further symmetric) pattern with respect to the central axis of the master template substrate 1100 such that the lines of different ones of the blazed diffraction grating pattern regions 1108 are parallel to each other within the blazed diffraction pattern region 1108 but extend in different radial directions with respect to the other blazed diffraction grating pattern regions 1108 on the same master template substrate 1100. When a set of lines of the blazed diffraction grating pattern region 1008 is allowed to extend in different directions not limited to the crystallographic directions of crystalline silicon, such as in the "windmill" arrangement illustrated in FIG. 11B, the substrate area can be utilized to define the device template regions 1104 in a much more efficient manner compared to the arrangement of the master template 1100A illustrated in FIG. 11A where a set of lines of different ones of the blazed diffraction grating pattern regions 1108 extend in the same direction. For illustrative purposes only, when the master template substrate 1100 is a 150 mm diameter silicon wafer and the device template regions 1104 have dimensions of 40 mm × 50 mm, the arrangement of the master template 1100A illustrated in FIG. 11A may be able to accommodate only up to four device template regions 1104, while the windmill arrangement of the master template 1100B illustrated in FIG. 11B can accommodate up to six device template regions 1104, thereby increasing the manufacturing throughput by 50%.Accordingly, in recognition of these and other advantages, the inventors have discovered the following manufacturing techniques, wherein the lines of the different blazed diffraction grating pattern regions 1108 extend in different directions, as described herein. (Fabrication of a primary master template for imprinting a blazed pattern on a master template substrate)

[0123] For example, single crystal substrates such as single crystal silicon (Si) wafers and single crystal germanium (Ge) wafers advantageously possess certain crystallographic attributes that can be used to fabricate a primary master template for imprinting a blazed diffraction grating pattern on a master template substrate. The single crystal substrate has a major substrate surface with a certain crystallographic orientation. Single crystal Si and Ge have a rhombohedral cubic lattice pattern structure, which is a two-interpenetrating face-centered cubic lattice pattern structure separated by 1 / 4 of the lattice constant along each axis of the unit cell. The crystallographic planes or facets of single crystals of Si and Ge can be denoted as (hkl) with respect to an individual plane or facet, or {hkl} with respect to a system of planes or facets, where h, k, and l are known as Miller indices. The angle (θ) between any two planes of the crystallographic planes or faces of single crystal Si and Ge can be defined. Different crystallographic planes of single crystal Si and Ge wafers have different surface densities of atoms and the bonding angles therebetween. As a result, different crystallographic planes have different physical properties such as different etching removal rates in a certain etching solution. The different etching rates and the angular relationships between different crystallographic planes in single crystal substrates such as Si and Ge wafers can, according to various embodiments, be used to fabricate a primary master template having a desired line shape for imprinting a blazed diffraction grating pattern on a master template substrate, as described below.

[0124] Some single crystal substrates, such as Si and Ge wafers, can be anisotropically etched in certain etching solutions, such as aqueous KOH solution and a mixture of ethylenediamine - pyrocatechol and hydrazine hydrate, to form preferential crystal facets. Advantageously, during these etchings, the etching process can utilize the property that some crystal planes, such as the {111} crystal plane, have a relatively high atomic density and a relatively low removal rate compared to some other crystal planes, such as the {100}, {110}, {211}, or {311} planes. Due to the different etching rates of different crystal planes, when the surface of a single crystal Si or Ge substrate is exposed to a suitable etching solution, for example, KOH, the initial etching profile can include a plurality of different crystal facets. However, after a certain time period, the etching profile becomes more dominated by the crystal plane with the slowest etching rate, which is the {111} crystal plane for Si and Ge. In combination with suitable mask techniques, the differential etching rate of different crystallographic planes can be used to form blazed diffraction grating lines with features, such as being asymmetric (e.g., having facets such as asymmetric facets similar to those in the blazed diffraction grating 1008 shown in FIG. 10A).

[0125] Figures 12A - 12C illustrate intermediate structures at different stages of an exemplary process for fabricating a primary master template by utilizing different etching rates of different crystallographic planes within a Si or Ge single - crystal substrate. Referring to Figure 12A, the intermediate structure 1200A includes a single - crystal substrate 1204, for example, a single - crystal Si substrate. The single - crystal substrate 1204 can be oriented to have a surface that belongs to one of a specific set of crystal planes, such as the {111}, {211}, {311}, {511}, {711}, or {100} family of crystal planes. In the illustrated embodiment, the single - crystal substrate 1204 is a Si wafer having a {100} surface orientation. The substrate 1204 can initially have a blanket etching mask layer 1208 formed thereon. The blanket etching mask layer 1208 can include one or more dielectric layers, such as SiO2 layer and / or Si3N4 layer. The dielectric layer can be deposited, for example, by chemical vapor deposition or thermally grown. To pattern the underlying blanket etching mask layer 1208, a photoresist layer 1212 can first be spin - coated on the blanket etching mask layer 1208 and subsequently patterned using a lithography technique, such as nanoimprint or optical lithography techniques.

[0126] Referring to the intermediate structure 1200B of FIG. 12B, using the patterned photoresist layer 1212, the blanket etching mask layer 1208 can be patterned to form a patterned etching mask layer 1208 having openings that expose the substrate 1204. To utilize different etching rates of different crystallographic planes to form a faceted structure, the etching mask layer 1208 may be patterned and have edges that are aligned in a certain crystallographic direction. For example, to form a faceted structure having a relatively slow etching {111} plane, the edges of the etching mask layer 1208 may be oriented parallel to the intersection of the surface plane and one of the four {111} planes. For example, on a {100}-oriented silicon wafer, the four planes of the {111} system of the plane intersect the {100} wafer surface at an angle of 54.7°. Thus, the etching mask layer 1208 can be patterned such that its edges are aligned with any of these intersecting lines.

[0127] FIG. 12C illustrates an intermediate structure 1200C that results after a substrate 1204 exposing a {100} surface is exposed to a solution containing KOH in an etchant, such as an isopropanol-water mixture, at a suitable temperature, such as about 70° C. When an etching mask layer 1208 is arranged as a stripe pattern having a side parallel to one of the intersections of the {001} plane and the {111} plane as described above, the etching of the exposed surface of the substrate 1204, once the facets of the etching profile are dominated by the rate-limiting slow-etching {111} plane, can result in the formation of triangular trenches or V-grooves, and the facets of the triangular trenches or V-grooves can be symmetric and can include one of the {111} facets. As illustrated in FIG. 12C, the facets of the triangular trenches can form symmetric angles with respect to the surface of the substrate or the x-y plane due to the angular relationship between the {111} plane and the {100} plane of the substrate surface. However, embodiments are not so limited, and by selecting substrates having different surface orientations, the trenches or grooves can be made asymmetric and / or non-triangular. FIGS. 13A-13C illustrate exemplary embodiments where the facets of the triangular trenches are asymmetric.

[0128] Some single crystal silicon or germanium substrates can be prepared or cut to have a surface with a crystallographic orientation that is not as common as the generally available {100}, {110}, or {111} orientations. These substrates are sometimes also referred to as “off-axis” wafers and can be oriented to have a surface such as a {211} or {311} surface, for example. When these substrates are etched using an etchant as described above, different crystal facets having different angles with respect to the substrate surface can be formed. Such etching characteristics can be utilized to form a primary master template having asymmetric surface angles, such as triangular lines or V-grooves, which can be used to process asymmetric structures, such as device master templates or intermediate master templates.

[0129] Figures 13A - 13C illustrate intermediate structures 1300A - 1300C at different stages of an exemplary process for machining a primary master template substrate using an off - axis wafer substrate, according to an embodiment. Referring to FIG. 13A, intermediate structure 1300A shows a single - crystal substrate 1304, for example, a single - crystal Si substrate having an off - axis surface. In the illustrated embodiment, single - crystal substrate 1304 may represent a Si wafer having a {311} surface orientation. The etching mask layer 1308 is patterned and can have openings that expose the substrate 1304 as described above with respect to FIGS. 12A and 12B. A detailed description of the process steps is not repeated here for the sake of brevity. FIG. 13C illustrates intermediate structure 1300C which is the result after the substrate 1304, having its {311} surface exposed, is exposed to an etching solution, for example, a solution containing KOH in an isopropanol - water mixture, at a suitable temperature, for example, about 70°C. When the etching mask layer 1308 is arranged as a striped pattern having sides parallel to some intersections formed by one of the {311} surface plane and the {111} plane as described above, the etching of the exposed surface of the substrate 1304 can result in the formation of triangular trenches or V - grooves once the faceting of the etching profile is governed by the rate - limiting slow - etching {111} plane. For example, intersections extending along the <110> - type direction formed by the {311} surface plane and the {111} plane can be used. Unlike the triangular trenches or V - grooves illustrated in intermediate structure 1200C (FIG. 12C) where the faceting of the triangular trenches or V - grooves are symmetric {111} faceting, in intermediate structure 1300C, the {111} faceting forms non - symmetric triangular trenches or V - grooves that form an angle of 70.5 o degrees with respect to each other. As illustrated in FIG. 13C, the faceting of the triangular trenches can form an asymmetric angle with respect to the surface of the substrate due to the angular relationship of the {111} plane with respect to the {311} orientation of the substrate surface.

[0130] Above, with respect to FIGS. 12A - 12C and FIGS. 13A - 13C, two exemplary process flows that result in two different triangular trenches or V - grooves in the Si substrate have been described for illustrative purposes only. However, the inventors have found that other blaze angles are also achievable based on the same concept of the present invention. Table 1 illustrates some examples of different facet angles that are achievable using Si wafers oriented at different angles to provide some examples. [Table 1]

[0131] Referring back to FIGS. 12C and 13C, in the illustrated embodiments, due to the finite width in the x - direction of the etching mask layers 1208, 1308, adjacent triangular trenches or V - grooves are separated by flat surfaces at the top of the individual substrates 1204, 1304. However, the embodiments are not so limited, and for various applications, it may be desirable to reduce or eliminate the flat surfaces between adjacent triangular trenches or V - grooves at the top of the substrates 1204, 1304. Thus, according to some embodiments, the width of the flat surface between adjacent triangular trenches can be reduced. Exemplary processes for reducing or eliminating the flat surfaces between adjacent triangular trenches or V - grooves are described below with respect to FIGS. 14A - 14C and FIGS. 15A - 15C.

[0132] Figures 14A-14C illustrate an exemplary process for reducing flat surfaces between adjacent triangular trenches. Referring to Figure 14A, a relatively wide section of the initial etching mask layer 1308 is first formed on the substrate 1304. Referring to Figure 14B, prior to etching the substrate 1304, the relatively wide etching mask layer 1308 can be trimmed or laterally shrunk to a desired width, for example, by isotropic etching. Referring to Figure 14C, after trimming and forming the etching mask layer 1308 with the desired width, the substrate 1304 is etched as described above to form triangular trenches or V-grooves until the facets mainly include {111} facets.

[0133] Figures 15A-15C illustrate another exemplary process for reducing flat surfaces between adjacent triangular trenches, which can be employed in addition to or instead of the exemplary process described with respect to Figures 14A-14C. In the illustrated exemplary process, after the flat region width is reduced by forming the etching mask layer 1308 and forming {111} facets as described above with respect to Figures 14A-14C and as shown in Figures 15A and 15B, the substrate 1304 can be further overetched until the triangular trenches or V-grooves are etched laterally beneath the etching mask layer 1308 as shown in Figure 15C. In some embodiments, the etching of the substrate 1304 may proceed until the edges of two adjacent triangular trenches or grooves contact each other such that the flat surface between adjacent triangular trenches is negligible, minimal, or non-existent. (Using the imprinted blazed diffraction pattern as a partial dry etching mask to etch the device master template substrate, processing of the device master template)

[0134] In the following, referring to FIGS. 16A - 16F, a master template for processing another master template or a master template for processing a blazed diffraction grating of an intermediate master template, e.g., a method for processing a device master template, is described using a primary master template that is processed according to the method described above with respect to FIGS. 12A - 12C, 13A - 13C, 14A - 14C, and 15A - 15C. The method for processing a device master template includes providing a device master template substrate 1100 (FIG. 16A) and imprinting periodically repeated lines 1614 (FIG. 16B) corresponding to a blazed diffraction grating pattern within a plurality of blazed diffraction grating regions 1604 (FIG. 16B) on the device master template substrate 1100, where the periodically repeated lines within different ones of the blazed diffraction grating regions 1604 extend in different directions. Thereafter, the pattern of the periodically repeated lines 1614 corresponding to the blazed diffraction grating pattern is transferred into the master template substrate, e.g., by dry etching using the imprinted lines as an etching template or a partial mask (FIG. 16D). Advantageously, since the periodically repeated lines are printed in a desired direction and subsequently transferred to the master template substrate 1100 by dry etching, the resulting blazed diffraction grating pattern can have lines extending in any direction within different ones of the blazed diffraction grating regions 1604, rather than being limited to the directions defined by crystallographic planes when processing the primary master template, as described above. Thus, as described above with respect to FIG. 11B, more efficient use of the substrate area is achieved, thereby increasing the throughput for processing optical elements having blazed diffraction gratings. Additional details of the method for processing the master template are described below with respect to each of FIGS. 16A - 16F.

[0135] Figures 16A - 16E illustrate top and cross-sectional views of intermediate structures at various stages of forming a device master template by imprinting a pattern on a device master template substrate and using the imprinted pattern as a partial mask to etch the device master template substrate. FIG. 16A illustrates an intermediate structure 1600A for processing a device master template, including a device master template substrate 1100. The top view illustrates a top view of the intermediate structure 1600A, and the bottom view illustrates a side view of the region where a blazed diffraction grating region 1604 (FIG. 16B) will be defined therein. The device master template substrate 1100 can be formed from any suitable material on which features can be imprinted. Advantageously, the disclosed method for forming the blazed diffraction grating pattern of the device master template does not rely on facet formation in the substrate by wet etching, so the device master template substrate 1100 need not be a crystalline substrate such as crystalline silicon. That is, the device master template substrate 1100 can be a crystalline substrate, such as a single crystalline substrate like a silicon wafer or a germanium wafer, but the embodiments are not so limited. The device master template substrate 1100 can also be, for example, a compound semiconductor, quartz, silica glass (e.g., doped silica glass), aluminum oxide (e.g., sapphire), plastic, polymer, or other suitable material on which features can be imprinted, such as a photoresist structure that can serve as a mask feature or a partial mask feature, as described below, and can be formed from other suitable crystalline or non-crystalline materials.

[0136] Similar to the device master template 1100B described above with respect to FIG. 11B, the illustrated intermediate structure 1600A includes a device master template substrate 1100 having a plurality of device template regions 1104 defined thereon, on which various optical elements, such as internal coupling and / or external coupling optical elements, will be formed. Different ones of the device template regions 1104 are arranged or extend in different non-orthogonal directions, for example, radially as illustrated. In the illustrated embodiment, the device template regions 1104 are radially arranged around a center with six-fold symmetry such that, in this example, the device template regions 1104 are arranged in a windmill configuration. As an example, adjacent ones of the six device template regions 1104 are, on average, rotated 60 o degrees relative to each other. However, the embodiments are not so limited, and the device template regions 1104 can be rotated, on average, by an angle having 360 o / n (where n is greater than 2, for example, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.) or any value between these values relative to each other, depending on the relative sizes of the device template regions 1104 and the size of the substrate 1100. That is, the device template regions 1104 can be arranged within n slices of the substrate 1100, and each of the n slices has 360 oForm a region, section, or compartment having sides that form an angle defined by / n. Thus, in various implementations, the plurality of device template regions 1104 may have rotational symmetry, for example, n-fold symmetry, such as 2-fold symmetry, 3-fold symmetry, 4-fold symmetry, 5-fold symmetry, 6-fold symmetry, 7-fold symmetry, 8-fold symmetry, 9-fold symmetry, 10-fold symmetry, 11-fold symmetry, 12-fold symmetry, etc., or any combination thereof and other values. When adjacent device template regions 1104 are rotated 90 degrees relative to each other, the number of device template regions 1104 in the layout of the device master template 1100B illustrated in FIG. 11B can be four, which matches the number of device template regions 1104 in the layout of the device master template 1100A illustrated in FIG. 11A. When the device template regions 1104 are rotated by an angle less than 90 degrees relative to each other, the number of device template regions 1104 in the layout illustrated in FIG. 11B can exceed the number of device template regions 1104 in the device master template 1100A (FIG. 11A). In the illustrated embodiment, only one device template region 1104 is arranged per 360 o / n regions or compartments (n = 6). However, the embodiments are not so limited, and in other embodiments, the plurality of device template regions 1104 can be arranged radially within each of the 360 o / n regions or compartments of the substrate 1100. Thus, depending on the number of regions or sections, the substrate area is divided, and depending on the number (m) of device template regions 1104 per region, there can be at least 2m numbers of device template regions 1104, such as 3m, 4m, 5m, 6m, 7m, 8m, 9m, 10m, 11m, 12m, etc. (m is at least 1).

[0137] In the illustrated embodiment, the device template regions 1104 are arranged in rotational symmetry. However, the embodiment is not so limited, and in other embodiments, the device template regions 1104 can be arranged asymmetrically. For example, adjacent device template regions 1104 may be separated by an irregular angular separation or formed at different radial distances from the central axis of the substrate 1100.

[0138] Referring to FIG. 16B, the intermediate structure 1600B represents the intermediate structure 1600A after the blazed diffraction grating regions 1604 are defined within or at corresponding locations for each of the device template regions 1104, thereby forming a blazed diffraction grating pattern 1614 within each of the blazed diffraction grating regions 1604. The upper figure illustrates a top-down view of the intermediate structure 1600B, and the lower figure illustrates a side view of the region including a portion of the blazed diffraction grating region 1604. As described above, the blazed diffraction grating pattern 1614 may be formed by a suitable imprinting technique, such as a nanoimprinting technique, which includes depositing a suitable blanket imprint mask layer 1608 (FIG. 16A), followed by imprinting the pattern using the primary master template 1612 as an imprint mold. The primary master template 1612 may be processed, for example, by forming faceted lines in crystalline silicon according to the process described above with respect to FIGS. 12A-12C, 13A-13C, 14A-14C, and 15A-15C. The primary master template 1612 serves as a nanoimprint mold and has a predetermined topological pattern configured to imprint the blazed diffraction grating pattern. The primary master template 1612 is brought into contact with and pressed into the blanket etching mask layer 1608. The blanket etching mask layer 1608 may be formed from a suitable deformable material, such as a polymeric material like photoresist. For example, the blanket etching mask layer 1608 may include a thermoplastic polymer. The primary master template 1612 may be pressed into the blanket etching mask layer 1608 at a temperature above, for example, the glass transition temperature of the blanket etching mask layer 1608. As a result, the pattern of the primary master template 1612 is transferred into the softened blanket etching mask layer 1608, thereby forming the imprinted blazed diffraction grating pattern 1614.For example, after being cooled to a temperature below the glass transition temperature of the blanket etching mask layer 1608, the primary master template 1612 is separated from the substrate 1100, while the imprinted blazed diffraction grating pattern 1614 remains on the substrate 1100. In the illustrated embodiment, the primary master template 1612 is rotationally pressed into the blanket etching mask layer 1608 n times, where n represents the number of blazed diffraction grating regions 1604 to be formed. The blazed diffraction grating pattern 1614, which comprises periodically repeated lines, can thus be imprinted in different locations corresponding to a plurality of device template regions 1104 in sequence by repeatedly contacting the primary master template 1612 and pressing it at different locations. After forming the n number of blazed diffraction grating regions 1604, in some techniques, after being pressed into the blanket etching mask layer 1608, the imprinted blazed diffraction grating pattern 1614 may be solidified by cross-linking under UV light.

[0139] Still referring to FIG. 16B, thus, the formed blazed diffraction grating region 1604 defines a substrate area in which lines of the blazed diffraction grating pattern 1614 are formed. As discussed above, advantageously, instead of being wet-etched into the crystalline substrate, the blazed diffraction grating pattern 1614, which comprises periodically repeated lines, is imprinted, so that the lines of the blazed diffraction grating pattern 1614, as described above with respect to FIG. 11A, are not limited to the crystallographic direction of the crystalline substrate in which each line of the blazed diffraction grating region 1008 extends in the same direction, but can extend in any suitable direction, as described above with respect to FIG. 11B. As described above with respect to FIG. 11B, advantageously, since the blazed diffraction grating pattern 1614 is printed, different ones of the blazed diffraction grating region 1604 can extend in any suitably different directions. In the illustrated embodiment, the lines of different ones of the blazed diffraction grating region 1604 extend in different radial directions. Allowing the lines of the blazed diffraction grating region 1604 to extend in different directions enables the device template regions 1104 to be arranged so that the area of the substrate 1104 is utilized much more efficiently, as in the illustrated "windmill" configuration, for example, similar to that described above with respect to FIG. 11B. In some such configurations, the angular separation between adjacent device template regions 1104 may be equal, however, in other configurations, the angular separation between adjacent device template regions 1104 may be unequal. For example, the angular spacing between two or more (possibly all) device template regions 1104 may be unequal.

[0140] Referring to FIG. 16C, for example, by spin coating a photoresist layer, substantially the entire surface of substrate 1104 is coated with masking layer 1618, and masking layer 1618 is locally opened in the area corresponding to blazed diffraction grating region 1604, thereby exposing imprinted blazed diffraction grating pattern 1614 while leaving other regions uncoated by masking layer 1618. Intermediate structure 1600C, which represents intermediate structure 1600B (FIG. 16B) after that, is shown. The openings may be formed, for example, by developing to locally expose the blazed diffraction grating region and locally remove masking layer 1618 from blazed diffraction grating region 1604. The upper figure shows a top view of intermediate structure 1600C, and the lower figure shows a side view of the region including a part of blazed diffraction grating region 1604.

[0141] After locally exposing imprinted blazed diffraction grating pattern 1614, intermediate structure 1600C (FIG. 16C) is placed in a plasma reactor configured for, for example, vapor phase plasma etching. In the plasma reactor, imprinted blazed diffraction grating pattern 1614 is used as a partial etching mask layer to transfer, at least in part, the structure of imprinted blazed diffraction grating pattern 1614 into underlying substrate 1100 in the exposed regions of imprinted blazed diffraction grating pattern 1614. The remaining regions remain covered by masking layer 1618, which serves as a complete etching mask layer to protect the remaining regions outside blazed diffraction grating region 1604.

[0142] As described herein, a partial etching mask layer refers to a mask layer having at least a portion of a layer that is not intended to maintain the coating of the underlying substrate against the etching solution throughout the duration of the etching process. Instead, at least some portions of the partial etching mask layer are designed to be completely removed at some point during the etching process such that the corresponding underlying substrate is partially removed during the etching process. For example, in FIG. 16C, when the imprinted blazed diffraction grating pattern 1614 is exposed to the etching solution under conditions where both the material of the imprinted blazed diffraction grating pattern 1614 and the substrate 1100 can be removed, the portion of the imprinted blazed diffraction grating pattern 1614 having a relatively thin thickness is first removed, thereby exposing the corresponding underlying substrate 1100 relatively early during the etching process. In response to the exposure, the exposed substrate region begins to be etched. Thereafter, different portions of the imprinted blazed diffraction grating pattern 1614 having a greater thickness are removed at different times, thereby exposing the corresponding underlying substrate at relatively different later times during the etching process. The result is that the pattern of the imprinted grating pattern 1614 is at least qualitatively transferred to the underlying substrate 1100.

[0143] Referring to FIG. 16D, the intermediate structure 1600D represents the intermediate structure 1600C (FIG. 16C) after substantially transferring the imprinted blazed diffraction grating pattern 1614 (FIG. 16C) into the underlying substrate 1100 using the imprinted grating pattern 1614 as a partial mask. The resulting intermediate structure 1600D comprises a dry-etched blazed diffraction grating pattern 1620. The upper view illustrates a top-down view of the intermediate structure 1600D, and the lower view illustrates a side view of a region including a portion of the blazed diffraction grating region 1604 comprising the dry-etched blazed diffraction grating pattern 1620 patterned into the substrate 1100.

[0144] Returning to FIGS. 16C and 16D, in the illustrated process, the imprinted blazed diffraction grating pattern 1614 is substantially transferred to the underlying substrate 1100 such that the resulting dry-etched blazed diffraction grating pattern 1620 has substantially the same shape as the imprinted blazed diffraction grating pattern 1614. However, the embodiments are not so limited, and in other embodiments, the dry-etched blazed diffraction grating pattern 1620 can deviate from the original shape of the imprinted blazed diffraction grating pattern 1614. For example, by controlling the relative etching rate of the imprinted blazed diffraction grating pattern 1614 to the material of the substrate 1100, the final shape of the dry-etched blazed diffraction grating pattern 1620 can be controlled. For example, depending on the chemistry of the etching, parameters such as the blaze angle δ, line width, and / or the width of the flat region between adjacent facets within the dry-etched blazed diffraction grating pattern 1620 can be different, e.g., 5%, 10%, 20%, 30%, 40%, 50%, or any percentage between these, or values outside of these percentages, smaller than the corresponding features within the imprinted blazed diffraction grating pattern 1614. Additionally, the angle of the lines of the dry-etched blazed diffraction grating pattern 1620 can be smoothed relative to the corresponding angles of the lines of the imprinted blazed diffraction grating pattern 1614.

[0145] Referring to FIG. 16E, the intermediate structure 1600E represents the intermediate structure 1600D (FIG. 16D) after the masking layer 1618 has been removed from the remaining area outside the dry-etched blazed diffraction grating pattern 1620. The upper view illustrates the top and bottom views of the intermediate structure 1600E, and the lower view illustrates a side view of the area including a part of the blazed diffraction grating region 1604 with the dry-etched blazed diffraction grating pattern 1620. The masking layer 1618 may be removed using a suitable dry and / or wet process. For example, when the masking layer 1618 is formed from a photoresist, oxidative reactive species such as reactive oxygen or fluorine species, e.g., oxygen or fluorine free radicals, are used to form volatile gases and removed by pressure feeding, and may be removed by a resist stripping or ashing process. The ashing or stripping process is carried out at a relatively high temperature to remove the mass of the photoresist, and then a descum process may follow, which is used to remove the residual photoresist in the trench. After removing the masking layer 1618, the intermediate structure 1600E may be cleaned in a suitable wet cleaning solution.

[0146] FIG. 16F illustrates a scanning electron microscope (SEM) image of an actual dry-etched blazed diffraction grating pattern resulting from the processing flow described above with respect to FIGS. 16A - 16E.

[0147] Thus, the dry-etched blazed diffraction grating pattern 1620 processed on the individual ones of the portions of the blazed diffraction grating region 1604 of the intermediate structure 1600E can, in turn, be used as a master template to form a blazed diffraction grating pattern on a final device substrate, e.g., a waveguide. The blazed diffraction grating pattern on the final device substrate may be formed using a suitable imprint technique, e.g., a nanoimprinting technique similar to those described above with respect to FIGS. 16A - 16B. Other processes are also conceivable.

[0148] In various embodiments disclosed herein, the final device substrate can be formed from a high refractive index material. High refractive index device substrates can provide various advantages. For example, when a high refractive index substrate serves as a waveguide having a relatively high refractive index, e.g., a refractive index of 2.0 or greater, the high refractive index substrate can provide, among other advantages, a relatively high field of view. In some embodiments, in order to efficiently couple light into the high refractive index waveguide, the diffractive optical coupling element correspondingly also has a high refractive index. To achieve this goal, among other advantages, some displays for AR systems according to the embodiments described herein include waveguides that include a relatively high refractive index (e.g., greater than or equal to 2.0) material having an individual diffraction grating formed thereon that correspondingly has a high refractive index, such as a Li-based oxide. For example, the diffraction grating may be formed on the waveguide by patterning a surface portion of the waveguide formed from the high refractive index material. As described herein, the high refractive index material can have a refractive index of at least 1.9, 2.0, 2.1, 2.3, 2.5, 2.7, or a value within a range defined by any of these values. The diffraction grating may be formed, for example, within a high refractive index material such as a Li-based oxide waveguide such as ZrO2, TiO2, SiC, or lithium niobate or lithium tantalate by patterning a high refractive index material-based waveguide with a blazed geometry.

[0149] Figures 17A and 17B illustrate SEM images of an actual blazed diffraction grating pattern formed on a device substrate that is imprinted using a dry-etched blazed diffraction grating pattern similar to that shown in Figure 16F as a device master template. The blazed diffraction grating pattern can be part of an optical element, such as an internal coupling grating (ICG), as discussed above.

[0150] In the above embodiments, the lines of the dry-etched blazed diffraction grating pattern, such as those described with respect to FIGS. 16A-16F, have a relatively simple blazed diffraction grating structure with facets having two main slopes, regardless of the presence or absence of flatness between those regions. However, the embodiments are not so limited, and the blazed diffraction grating pattern can have lines having different shapes. FIGS. 18A-18B illustrate cross-sectional views of intermediate structures 1814, 1820 at different stages of forming a device master template by imprinting a pattern on a substrate, using the imprinted pattern as a partial mask to etch the substrate, and producing lines having an alternating shape. FIGS. 18A and 18B illustrate the intermediate structures 1814, 1820 corresponding to the processing steps described above with respect to FIGS. 16C and 16D. In the intermediate structures illustrated in FIGS. 18A and 18B, unlike the intermediate structures illustrated with respect to FIGS. 16C and 16D, the lines of the imprinted blazed diffraction grating pattern 1814 (FIG. 18A) and the corresponding dry-etched blazed diffraction grating pattern 1820 (FIG. 18B) have a stepped structure. The shapes are different, but the principle and steps of its processing are similar to those described above with respect to FIGS. 16A-16F, and the details are not repeated here for the sake of brevity.

[0151] FIG. 19A shows an SEM image of an actual intermediate structure resulting from a processing flow similar to that described above with respect to FIGS. 18A-18B, which yields a device master template in which the lines of the blazed diffraction grating pattern have a stepped structure. The lines shown have two steps, but the embodiments are not so limited and additional steps may be formed. As shown and described above, by controlling the relative etching rate of the imprinted blazed diffraction grating pattern 1814 to the material of the substrate 1100, the final shape of the dry-etched blazed diffraction grating pattern 1820 can be controlled. For example, depending on the chemistry of the etching, parameters such as the angle and width of the steps and the overall line width between the dry-etched blazed diffraction grating patterns 1820 can differ from the corresponding features within the imprinted blazed diffraction grating pattern 1814. Additionally, the angle of the lines of the dry-etched blazed diffraction grating pattern 1820 may be smoothed with respect to the lines of the imprinted blazed diffraction grating pattern 1814. The left and right SEM images represent intermediate structures resulting from two different dry-etching recipes from the same imprinted blazed diffraction grating pattern.

[0152] FIG. 19B is an SEM image of an actual blazed diffraction grating pattern that could be part of an internal coupled grating (ICG) formed using the dry-etched blazed diffraction grating pattern shown in FIG. 19A as a device master template.

[0153] FIG. 20 illustrates a schematic full wafer representation of the location of an experimental exemplary blazed diffraction grating 2004 (“dual replicated internal coupled (IC) optical grating”) processed by imprinting using a device master template processed according to an embodiment. Each of the blazed diffraction gratings 2004 was processed on a 1,500 mm high refractive index glass wafer (n~1.8) using a device master template, which is similar to those shown in FIGS. 17A and 17B and is processed using a process similar to that described above with respect to FIGS. 16A-16E. As a comparison, a control diffraction grating 2008 (“control internal coupled (IC) optical grating”) was also processed on the same wafer substrate from a primary master template using a direct imprinting technique. On average, the experimental blazed diffraction gratings 2004 processed using a device master template processed according to an embodiment of the processes described herein exhibited matching performance compared to the control diffraction gratings 2008 processed directly from the primary master template. (Fabrication of Device Master Template by Coating Imprinted Blazed Diffraction Pattern)

[0154] For example, as described above with respect to FIGS. 16C and 16D, an imprinted blazed diffraction grating pattern 1614 formed from a material that can serve as an etching mask, e.g., a photoresist material, is advantageously used as a partial etching mask to etch the underlying substrate. The resulting dry-etched blazed diffraction grating pattern 1620 serves as a rigid device master template for imprinting the blazed diffraction grating pattern on a device substrate. As an alternative process, instead of dry etching, to etch the blazed diffraction grating pattern into the substrate, the imprinted blazed diffraction grating pattern 1614 itself can be made rigid, e.g., by coating, and used as a device master template for imprinting the blazed diffraction grating pattern on a device substrate, as described below.

[0155] Figures 21A and 21B illustrate a process flow for fabricating a device master template by imprinting a blazed diffraction grating pattern on a device master substrate, coating the pattern with a hard thin film, and then imprinting a blazed diffraction grating on a device substrate using the resulting device master template. Referring to FIG. 21A, the process includes providing a primary master template 2104 (cross-sectional view) that includes a blazed diffraction grating pattern that is fabricated by forming faceted lines in crystalline silicon according to a process similar to that described above with respect to FIGS. 12A-12C, 13A-13C, 14A-14C, and 15A-15C (the details of which are not repeated here for brevity). The primary master template 2104 serves as a nanoimprint mold, which has a predetermined topology pattern (represented as regions having a faceted triangular topology) configured to imprint a blazed diffraction grating pattern, as described above with respect to FIG. 16A. In the illustrated embodiment, the primary master template 2104 includes other device patterns (represented as regions having a rectangular topology) in addition to the blazed diffraction grating pattern that includes faceted lines. The blazed diffraction grating pattern can serve as a mold for one of the optical elements, e.g., for an internal coupling optical element, while the other device patterns can include various other optical or non-optical elements. For example, the other optical elements may include light dispersing elements (730, 740, 750, FIGS. 9A-9C) and / or external coupling optical elements (800, 810, 820, FIGS. 9A-9C).

[0156] Still referring to FIG. 21A, an intermediate structure 2108A / 2108B of a device master template having a plurality of device template regions 1104 is processed using a primary master template 2104. The lower intermediate structure 2108B represents a top view showing the entire substrate of the device master template including a plurality of device template regions 1104, while the upper intermediate structure 2108A represents a side view showing a part of one of the device template regions 1104 including a blazed diffraction grating pattern region 2112A and a pattern region 2112B for other optical elements. The intermediate structure 2108A / 2108B includes an imprinted pattern layer 2112, which may be formed using the primary master template 2104 through a nanoimprint process similar to that described above with respect to FIGS. 16A and 16B (the details are not repeated here for brevity). Different from FIG. 16B, in the illustrated embodiment, the imprinted pattern 2112 of the intermediate structure 2108A / 2108B includes a pattern region 2112B for other optical elements in addition to the blazed diffraction grating pattern region 2112A (1604 in FIG. 16B). When the blazed diffraction grating pattern region 2112A is configured to form one of the optical elements, for example, an internal coupling optical element, the pattern region 2112B can be configured to form various other optical or non-optical elements, such as a light dispersing element and / or an external coupling optical element.

[0157] As described above with respect to FIG. 16A, the primary master template 2104 is pressed n times into a blanket etch mask layer, for example, a photoresist layer, at different portions of the blazed diffraction grating region, where n represents the number of device template regions 1104 to be formed. When the device template regions 1104 are arranged in a windmill configuration as described above with respect to FIG. 16B, the primary master template 2104 may be rotated around the substrate during different presses into the blanket etch mask layer in the manner described above with respect to FIG. 16B (the details are not repeated here for brevity).

[0158] Referring to FIG. 21B, after forming n device template regions 1104 each including an imprinted pattern layer 2112 that includes a blazed diffraction grating region 2112A and a pattern region 2112B for other optical elements respectively, the surface of the imprinted pattern layer 2112 is coated with a coating 2120 to complete the fabrication of the device master template 2116. The illustrated device master template 2116 represents an intermediate structure 2108A illustrated in FIG. 21A after the coating layer 2120 is formed. The coating 2120 may be formed from any suitable material that provides the imprinted pattern layer 2112 with suitable hardness and rigidity so that the resulting coated imprinted pattern layer 2112 can serve as a device master template. Suitable materials include, for example, dielectric materials including SiO2, Si3N4, SiC, HfO2, Al2O3, etc., semiconductor materials including silicon, germanium, etc., metals including tungsten, aluminum, copper, titanium, gold, chromium, etc., metal nitrides, for example tin, or metal alloys including, for example, AuPd and PdAgCu. Suitable processes for forming the coating 2120 include, inter alia, chemical vapor deposition (CVD), plasma enhanced chemical vapor deposition (PE-CVD), high density chemical vapor deposition (HDP-CVD), thermal atomic layer deposition (ALD), plasma enhanced atomic layer deposition (PE-ALD), spin-on dielectric process (SOD), and physical vapor deposition (PVD). The suitable process for forming the coating 2020 may be a low temperature (e.g., <450° C.) process so that the imprinted pattern layer 2112 is not damaged or overly oxidized during the coating process. The coating 2120 provides sufficient mechanical rigidity and hardness so that the coated imprinted pattern layer 2112 can serve as a device master template pattern. The step of forming the coating 2120 completes the fabrication of the device master template 2116.

[0159] Still referring to FIG. 21B, a final device pattern layer 2132 may be formed on device substrates 2124A / 2124B using a device master template 2116 having a coated imprinted pattern layer 2112 formed thereon. The lower device substrate 2124B represents a top view of the device substrate including a plurality of device regions 2128, while the upper device substrate 2124A represents a side view of the device substrate showing a part of one of the device regions 2128. The device substrate 2124A shows a device pattern layer 2132 including a blazed diffraction grating region 2132A and a region 2132B including other optical elements. The device pattern layer 2132 may be formed using the device master template 2116 through a nanoimprint process similar to that described above with respect to FIGS. 16A and 16B (the details of which are not repeated here for brevity). Thus, each of the device substrates 2124A / 2124B to be processed has n number of device regions 2128 formed thereon, each including a device pattern layer 2132 including a blazed diffraction grating region 2132A and a region 2132B including other optical elements. For example, the blazed diffraction grating region 2132A can form a part of one of an internal coupling optical element, e.g., ICG, and an external coupling optical element, e.g., EPE, while the region 2132B can form the other of the internal coupling optical element, e.g., ICG, and the external coupling optical element, e.g., EPE, and a part of a light dispersing element and other optical elements.

[0160] Figures 22A - 22D illustrate an alternative process flow for fabricating a device master template and a blazed diffraction grating on a device substrate. Similar to the process flow described above with respect to Figures 21A and 21B, the process flow includes imprinting a blazed diffraction grating pattern on a device master substrate, coating the pattern with a hard thin film, and using the resulting device master template to imprint a blazed diffraction grating on the device substrate. However, unlike the process flow of Figures 21A and 21B, in the process flow described with respect to Figures 22A - 22D, the blazed diffraction grating pattern region 2112A (Figure 21A) and the pattern region 2112B (Figure 21A) for other optical elements are formed in separate process steps using an intermediate master template, as described below.

[0161] Referring to FIG. 22A, the process includes providing a primary master template 2204 (cross-sectional view) that includes a blazed diffraction grating pattern, which is processed by forming faceted lines in crystalline silicon according to a process similar to that described above with respect to FIGS. 12A-12C, 13A-13C, 14A-14C, and 15A-15C (the details of which, for brevity, are not repeated here). The primary master template 2204 serves as a nanoimprint mold for imprinting the blazed diffraction grating pattern, as described above with respect to FIG. 21A. However, unlike the master template described above with respect to FIG. 21A, in the illustrated embodiment, the primary master template 2204 includes a blazed diffraction grating pattern that includes faceted lines, while not including other device patterns. Using the primary master template 2204, intermediate structures 2208A, 2208B of an intermediate master template that include a plurality of device template regions are processed. The lower intermediate structure 2208B represents a top view showing the entire substrate of the device master template that includes a plurality of device template regions, while the upper intermediate structure 2208A represents a side view showing a part of one of the device template regions that includes a blazed diffraction grating pattern region. The intermediate structures 2208A / 2208B include an imprinted pattern layer, which may be formed using the primary master template 2204 through a nanoimprint process similar to that described above with respect to FIGS. 16A and 16B (the details of which, for brevity, are not repeated here). As described above with respect to FIG. 16A, the primary master template 2204 is pressed into a blanket etch mask layer, for example, a photoresist layer, n times at different portions of the blazed diffraction grating region, where n represents the number of device template regions to be formed.When the device template region is arranged in the windmill configuration, similar to that described above with respect to FIG. 16B, the primary master template 2204 may be rotated around the substrate during different presses into the blanket etching mask layer in the manner described above with respect to FIG. 16B (the details are not repeated here for the sake of brevity).

[0162] Referring to FIG. 22B, after forming n device template regions each including a blazed diffraction grating region, the surface of the imprinted pattern layer is coated (represented by the thick black line) using a process and materials similar to those described above with respect to FIG. 21B (the details are not repeated here for the sake of brevity). The coating completes the second master template 2212, which is an intermediate master template. Using the second master template 2212, an intermediate structure 2216A (side view) / 2216B (top view) for the third master template is processed. The intermediate structure 2216A / 2216B is processed by imprinting a blazed diffraction grating pattern having a pattern region pre-formed thereon similar to the pattern region 2112B (FIG. 21A) for other optical elements onto the substrate.

[0163] Referring to FIG. 22C, after the intermediate structure 2216A / 2216B is processed by imprinting a blazed diffraction grating pattern on a substrate having a pattern area previously formed thereon, the surface of the imprinted pattern layer is coated (represented by the thick black line) using a process similar to that described above with respect to FIG. 21B (the details of which are not repeated here for brevity). The coating completes a third master template, the intermediate master template 2220. Using the third master template 2220, an intermediate structure 2108A (side view) / 2108B (top view) for a fourth master template is processed. The intermediate structure 2108A / 2108B is processed by imprinting a blazed diffraction grating pattern and a certain pattern on a device master substrate. At this stage, the intermediate structure 2108A / 2108B is the same as the intermediate structure 2108A / 2108B described above with respect to FIG. 21A, which includes a blazed diffraction grating pattern area 2112A and a pattern area 2112B for other optical elements.

[0164] Referring to FIG. 22D, the coating 2120 is formed on the intermediate structure 2108A / 2108B in the same manner as described above with respect to FIGS. 21A and 21B, forming the device master template 2116. Thereafter, using the device master template 2116 having the coated imprinted pattern layer 2112 formed thereon, the final device pattern layer 2132 can be formed on the device substrates 2124A / 2124B in the same manner as described above with respect to FIGS. 21A and 21B (the details are not repeated here for the sake of brevity). When processed in this way, the device substrates 2124A / 2124B each include the device pattern layer 2132 including a blazed diffraction grating region 2132A and a region 2132B including other optical elements, and have n device regions 2128 formed thereon. For example, the blazed diffraction grating region 2132A can form a part of one of the internal coupling optical elements, such as ICG, and the external coupling optical elements, such as EPE, while the region 2132B can form the other of the internal coupling optical elements, such as ICG, and the external coupling optical elements, such as EPE, and a part of the light dispersion element and other optical elements. (Blazed diffraction grating structure processed using a device master template processed by imprinting)

[0165] The blazed diffraction gratings processed using the device master template described above can have various dimensions and configurations, as described with reference to FIG. 10A. Referring back to FIG. 10A, the blazed diffraction grating lines 1012 can have a height (H) that, according to an embodiment, is within a range defined by 5 nm to 50 nm, 50 nm to 100 nm, 100 nm to 150 nm, 150 nm to 200 nm, 200 nm to 250 nm, or any of these values. The blazed diffraction grating lines 1012 can be periodically repeated with a pitch d within a range defined by 100 nm to 200 nm, 200 nm to 300 nm, 300 nm to 400 nm, 400 nm to 500 nm, 500 nm to 600 nm, 600 nm to 700 nm, 700 nm to 800 nm, 800 nm to 900 nm, 900 nm to 1 μm, or any range defined by any of these values, according to various embodiments.

[0166] As described above, the blazed diffraction grating lines 1012 can have two facets formed at a relatively shallow angle δ with respect to the plane of the substrate at an angle within a range defined by, for example, about 20°, 30°, 40°, 50°, 60°, or any value within a range defined by these values, of one of a plurality of facets, as shown in the illustrated embodiment. For example, as shown in Table 1, when the substrate is a silicon wafer formed such that the lines 1012 are formed so that the facets have {211}, {311}, {511}, {711}, or {100} surface planes, the resulting angle δ can be about 22.4°, 29.5°, 38.9°, 43.3°, or 54.7°, respectively. Values outside the angles shown above are also considered possible.

[0167] According to various embodiments, when configured as an internal coupling optical element or an internal coupling diffraction grating, the blazed diffraction grating structure formed as such can diffractively couple light incidence into the substrate 1004 as shown in FIG. 10B, which can be a waveguide as described above. On the other hand, when configured as an external coupling optical element, the blazed diffraction grating structure formed as such can diffractively couple light from the substrate 1004, which can be a waveguide as described above, into the user's field of view.

[0168] A wide range of variations are conceivable. For example, although the blazed diffraction grating is discussed above, the diffraction characteristics may be different and the diffraction grating need not be blazed. In addition, in any of the processes described herein, the features formed may be either positive or negative. For example, in any of the processes described herein, the features formed may correspond to the diffraction pattern of the diffraction grating or may be the negative thereof. Such a negative pattern may be used to form a positive pattern in an intermediate template or in the diffraction grating itself. In addition, any number of intermediate structures, such as an intermediate master template, may be used within a given process. Such an intermediate structure, for example, an intermediate master template, may include a positive or negative of the diffraction pattern formed in the final device. Still other variations are also conceivable. (Additional Examples) (Example 1) A method of processing a blazed diffraction grating, providing a master template substrate; imprinting periodically repeated lines on the master template substrate within a plurality of master template regions, wherein the periodically repeated lines in different ones of the master template regions extend in different directions; using at least one of the master template regions as a master template to imprint at least one blazed diffraction grating pattern on a grating substrate; comprising. (Example 2) The periodically repeated lines within different master template regions extend in non - orthogonal directions, according to the method described in Example 1. (Example 3) The periodically repeated lines within adjacent master template regions extend in a direction forming an angle of 0 to 90 degrees, according to the method described in any one of the preceding embodiments. (Example 4) The periodically repeated lines within different master template regions extend in different radial directions with respect to the central axis of the master template substrate, according to the method described in any one of the preceding embodiments. (Example 5) The step of imprinting the periodically repeated lines on the master template substrate includes the step of imprinting within at least four master template regions, according to the method described in any one of the preceding embodiments. (Example 6) The step of imprinting the periodically repeated lines includes the step of imprinting across the silicon surface of the master template substrate, according to the method described in any one of the preceding embodiments. (Example 7) The step of imprinting the periodically repeated lines includes the step of imprinting across the silicon oxide surface of the master template substrate, according to the method described in any one of the preceding embodiments. (Example 8) The step of imprinting the periodically repeated lines on the master template substrate includes the step of sequentially imprinting within different ones of a plurality of master template regions using the same primary master template, according to the method described in any one of the preceding embodiments. (Example 9) The periodically repeated lines formed on the master template substrate have a saw - tooth profile, according to the method described in any one of the preceding embodiments. (Example 10) The method according to any one of the preceding embodiments, wherein the periodically repeated lines formed on the master template substrate have symmetric opposing surfaces that form similar angles with respect to the plane of the master template substrate. (Example 11) The method according to any one of the preceding embodiments, wherein the periodically repeated lines formed on the master template substrate have asymmetric opposing surfaces that form different angles with respect to the plane of the master template substrate. (Example 12) The method according to any one of the preceding embodiments, wherein the periodically repeated lines formed on the master template substrate have opposing surfaces that have different inclinations with respect to the plane of the major surface of the master template substrate. (Example 13) The method according to any one of the preceding embodiments, wherein the periodically repeated lines formed on the master template substrate have side surfaces having a stepped structure. (Example 14) The method according to any one of the preceding embodiments, wherein the periodically repeated lines formed on the master template substrate contain a polymer material. (Example 15) The method according to any one of the preceding embodiments, wherein the periodically repeated lines formed on the master template substrate contain a dielectric material. (Example 16) The method according to any one of the preceding embodiments, further comprising the step of coating the periodically repeated lines formed on the master template substrate with a dielectric material. (Example 17) The method according to any one of Embodiments 1-15, further comprising the step of coating the periodically repeated lines formed on the master template substrate with a metal oxide or a metal nitride. (Example 18) The method according to any one of Embodiments 1-15, further comprising the step of coating the periodically repeated lines formed on the master template substrate with a metal or a metal alloy. (Example 19) The method according to any one of the preceding embodiments, further comprising the step of transferring a pattern corresponding to a periodically repeated line into a master template substrate. (Example 20) The step of transferring the pattern includes the method according to Example 19, which includes using the periodically repeated line as a partial mask to dry-etch the master template substrate. (Example 21) The step of dry-etching includes the method according to Example 20, which includes locally dry-etching the master template region. (Example 22) The step of imprinting the periodically repeated line includes the method according to any one of the preceding embodiments, which includes using a primary master template provided with the periodically repeated line formed on a primary master substrate to perform imprinting. (Example 23) The periodically repeated line formed on the primary master substrate has a sawtooth profile, according to the method of Example 22. (Example 24) The periodically repeated line formed on the primary master substrate has a laterally oriented side surface, according to the method of Example 22 or 23. (Example 25) The primary master substrate includes a silicon substrate, according to the method of Example 22 or 24. (Example 26) The primary master substrate is a silicon substrate having a major surface with a (311) crystal orientation, according to any one of Examples 22-25. (Example 27) The periodically repeated line formed on the primary master substrate has a facet with a (111) crystal orientation, according to the method of Example 26. (Example 28) The method according to any one of Examples 25-27, further comprising the step of forming a primary master template by lithographically patterning and etching a silicon substrate. (Example 29) The step of etching the silicon substrate is the method described in Example 28, including wet etching. (Example 30) The periodically repeated lines formed on the primary master substrate are the method described in Example 22 or 23, including a polymer material coated with a dielectric material. (Example 31) The grating substrate is a transparent substrate, and the method is described in any one of the preceding embodiments. (Example 32) The grating substrate has a refractive index greater than about 1.4, and the method is described in any one of the preceding embodiments. (Example 33) The grating substrate includes a waveguide, and the method is described in any one of the preceding embodiments. (Example 34) The blazed diffraction grating is the method described in Example 33, including an internal coupling grating configured to internally couple light into the waveguide. (Example 35) The blazed diffraction grating is the method described in Example 33, including an external coupling grating configured to externally couple light from the waveguide. (Example 36) The blazed diffraction grating is the method described in Example 33, including a light dispersing element configured to disperse light and propagate it towards an external coupling element within the waveguide. (Example 37) The blazed diffraction grating is the method described in Example 33, configured to disperse light and propagate it within the waveguide, and further configured to externally couple light from the waveguide, serving as a combined external coupling grating and light dispersing element. (Example 38) The blazed diffraction grating pattern is the method described in any one of the preceding embodiments, having a geometric shape configured to have a primary diffraction efficiency greater than 50% for at least one polarization of light. (Example 39) The step of imprinting at least one blazed diffraction grating pattern includes, simultaneously, the step of imprinting two or more blazed diffraction grating patterns, the method according to any one of the preceding embodiments. (Example 40) The at least one blazed diffraction grating pattern comprises a plurality of straight lines, the method according to any one of the preceding embodiments. (Example 41) The at least one blazed diffraction grating pattern comprises a plurality of discontinuous lines, the method according to any one of embodiments 1-39. (Example 42) The at least one blazed diffraction grating pattern comprises a plurality of pillars protruding from the surface of the grating substrate, the method according to any one of embodiments 1-39. (Example 43) The at least one blazed diffraction grating pattern comprises a plurality of straight lines, and at least some of the straight lines have different widths, the method according to any one of embodiments 1-39. (Example 44) The at least one blazed diffraction grating pattern comprises diffraction features arranged as a one-dimensional (1D) array having periodicity in one lateral direction, the method according to any one of embodiments 1-39. (Example 45) The 1D array serves as a 1D grating configured to preferentially diffract light in one direction, the method according to Example 44. (Example 46) The at least one blazed diffraction grating pattern comprises diffraction features arranged as a two-dimensional (2D) array having periodicity in two lateral directions, the method according to any one of embodiments 1-39. (Example 47) The 2D array serves as a 2D grating configured to preferentially diffract light in two directions, the method according to Example 46. (Example 48) The 2D array has the same number of diffraction features in two different lateral directions, the method according to Example 46. (Example 49) A method of processing a master template for imprinting a blazed diffraction grating, comprising the step of providing a master template substrate, providing a primary master template comprising periodically repeated lines formed on the primary master substrate, using the primary master template within a plurality of master template regions to imprint periodically repeated lines onto the master template substrate, wherein the periodically repeated lines within different ones of the master template regions extend in different directions, A method comprising. (Example 50) The method according to Example 40, wherein the periodically repeated lines formed on the primary master substrate have a sawtooth profile. (Example 51) The method according to Example 40 or 50, wherein the periodically repeated lines formed on the primary master substrate have laterally surfaces that are asymmetrically oriented. (Example 52) The method according to any one of Examples 40 - 51, wherein the primary master substrate is a silicon substrate having a major surface with a (311) crystal orientation. (Example 53) The method according to Example 52, wherein the periodically repeated lines formed on the primary master substrate have facets with a (111) crystal orientation. (Example 54) The method according to any one of Examples 40 - 53, wherein the step of providing the primary master template comprises lithographically patterning and etching periodically repeated lines into a silicon substrate. (Example 55) The method according to Example 54, wherein the step of etching the silicon substrate comprises wet etching. (Example 56) The step of providing a primary master template includes the steps of forming periodically repeated lines including a polymer material and coating the periodically repeated lines with a dielectric material, according to any one of embodiments 40-51. (Example 57) The periodically repeated lines within different master template regions extend in non-orthogonal directions, according to any one of embodiments 40-56. (Example 58) The periodically repeated lines within different master template regions extend in a direction radially symmetric with respect to the central axis of the master template substrate, according to any one of embodiments 40-57. (Example 59) The step of imprinting the periodically repeated lines onto the master template substrate includes the step of imprinting within at least four master template regions, according to any one of embodiments 40-58. (Example 60) The periodically repeated lines formed on the master template substrate have a sawtooth profile, according to any one of embodiments 40-59. (Example 61) The periodically repeated lines formed on the master template substrate have symmetric opposing side surfaces that form similar angles with respect to the plane of the master template substrate, according to any one of embodiments 49-60. (Example 62) The periodically repeated lines formed on the master template substrate have asymmetric opposing side surfaces that form different angles with respect to the plane of the master template substrate, according to any one of embodiments 40-60. (Example 63) The periodically repeated lines formed on the master template substrate have opposing side surfaces that have different inclinations with respect to the plane of the major surface of the master template substrate, according to any one of embodiments 40-61. (Example 64) The method according to any one of Examples 40-63, wherein the periodically repeated lines formed on the master template substrate have a stepped structure and side surfaces. (Example 65) The method according to any one of Examples 40-64, wherein the periodically repeated lines formed on the master template substrate contain a polymer material. (Example 66) The method according to any one of Examples 40-65, wherein the periodically repeated lines formed on the master template substrate contain a dielectric material. (Example 67) The method according to any one of Examples 40-66, further comprising the step of coating the periodically repeated lines formed on the master template substrate with a dielectric material. (Example 68) The method according to any one of Examples 40-66, further comprising the step of coating the periodically repeated lines formed on the master template substrate with a metal oxide or a metal nitride. (Example 69) The method according to any one of Examples 40-66, further comprising the step of coating the periodically repeated lines formed on the master template substrate with a metal or a metal alloy. (Example 70) The method according to any one of Examples 49-69, further comprising the step of transferring the pattern corresponding to the periodically repeated lines into the master template substrate. (Example 71) The method according to Example 70, wherein the step of transferring the pattern includes the step of dry etching the master template substrate. (Example 72) The method according to Example 71, wherein the step of dry etching includes the step of locally dry etching the master template region. (Example 73) The master template region is configured to internally couple light into the waveguide, includes an internal coupling grating, and is configured to imprint a blazed diffraction grating, according to the method of any one of Embodiments 49-72. (Embodiment 74) The master template region is configured to externally couple light from the waveguide, includes an external coupling grating, and is configured to imprint a blazed diffraction grating, according to the method of any one of Embodiments 49-72. (Embodiment 75) The master template region is configured to disperse light and propagate it towards an external coupling element within the waveguide, includes a light dispersion element, and is configured to imprint a blazed diffraction grating, according to the method of any one of Embodiments 49-72. (Embodiment 76) The master template region is configured to disperse light and propagate it within the waveguide, and further configured to externally couple light from the waveguide, serving as a combined external coupling grating and light dispersion element, and is configured to imprint a blazed diffraction grating, according to the method of any one of Embodiments 49-72. (Embodiment 77) The master template region includes a plurality of straight lines and is configured to imprint a blazed diffraction grating, according to the method of any one of Embodiments 49-72. (Embodiment 78) The master template region includes a plurality of discontinuous lines and is configured to imprint a blazed diffraction grating, according to the method of any one of Embodiments 49-72. (Embodiment 79) The master template region includes a plurality of pillars protruding from the surface of the grating substrate and is configured to imprint a blazed diffraction grating, according to the method of any one of Embodiments 49-72. (Embodiment 80) The master template region is configured to imprint a blazed diffraction grating with a plurality of straight lines, and at least some of the straight lines have different widths, according to the method of any one of Examples 49 - 72. (Example 81) The master template region is configured to imprint a blazed diffraction grating with diffraction features arranged as a one-dimensional (1D) array having periodicity in one lateral direction, according to the method of any one of Examples 49 - 72. (Example 82) The 1D array serves as a 1D grating configured to preferentially diffract light in one direction, according to the method of Example 81. (Example 83) The master template region is configured to imprint a blazed diffraction grating with diffraction features arranged as a two-dimensional (2D) array having periodicity in two lateral directions, according to the method of any one of Examples 49 - 72. (Example 84) The 2D array serves as a 2D grating configured to preferentially diffract light in two directions, according to the method of Example 83. (Example 85) The 2D array has the same number of diffraction features in two different lateral directions, according to the method of Example 83. (Example 86) A method for processing a diffraction grating, providing a master template substrate; imprinting periodically repeated lines in one or more master template regions on the master template substrate, the periodically repeated lines being formed from a first material; coating the periodically repeated lines with a second material having a hardness greater than that of the first material; using the one or more master template regions as a master template to imprint one or more blazed diffraction grating patterns on a grating substrate; comprising the method. (Example 87) The step of imprinting periodically repeated lines is the step of imprinting within a plurality of master template regions, wherein the periodically repeated lines within different master template regions extend in different directions, the method according to Example 86, comprising the step. (Example 88) The periodically repeated lines within different master template regions extend in different radial directions with respect to the central axis of the master template substrate, the method according to Example 86 or 87. (Example 89) The step of imprinting periodically repeated lines on the master template substrate comprises the step of imprinting within at least four master template regions, the method according to any one of Examples 86 - 88. (Example 90) The periodically repeated lines formed on the master template substrate have symmetric opposing side surfaces that form similar angles with respect to the plane of the master template substrate, the method according to any one of Examples 86 - 89. (Example 91) The periodically repeated lines formed on the master template substrate have asymmetric opposing side surfaces that form different angles with respect to the plane of the master template substrate, the method according to any one of Examples 86 - 89. (Example 92) The periodically repeated lines formed on the master template contain a polymer material, the method according to any one of Examples 86 - 91. (Example 93) The periodically repeated lines formed on the master template substrate contain a dielectric material, the method according to any one of Examples 86 - 91. (Example 94) The method according to any one of Examples 86 - 91 further comprises the step of coating the periodically repeated lines formed on the master template substrate with a dielectric material. (Example 95) The method according to any one of Examples 86 - 91, further comprising coating periodically repeated lines formed on a master template substrate with a metal oxide or a metal nitride. (Example 96) The method according to any one of Examples 86 - 91, further comprising coating periodically repeated lines formed on a master template substrate with a metal or a metal alloy. (Example 97) The method according to any one of Examples 86 - 96, comprising an external coupling grating, wherein the blazed diffraction grating is configured to externally couple light from a waveguide. (Example 98) The method according to any one of Examples 86 - 96, comprising an optical dispersion element, wherein the blazed diffraction grating is configured to disperse light and propagate it toward an external coupling element within a waveguide. (Example 99) The method according to any one of Examples 86 - 96, comprising a combined external coupling grating and optical dispersion element, wherein the blazed diffraction grating is configured to disperse light and propagate it within a waveguide, and further configured to externally couple light from the waveguide. (Example 100) The method according to any one of Examples 86 - 99, wherein one or more blazed diffraction grating patterns comprise a plurality of straight lines. (Example 101) The method according to any one of Examples 86 - 99, wherein one or more blazed diffraction grating patterns comprise a plurality of discontinuous lines. (Example 102) The method according to any one of Examples 86 - 99, wherein one or more blazed diffraction grating patterns comprise a plurality of pillars protruding from the surface of a grating substrate. (Example 103) The method according to any one of Examples 86 - 99, wherein one or more blazed diffraction grating patterns comprise a plurality of straight lines, and at least some of the straight lines have different widths. (Example 104) The method according to any one of embodiments 86-99, wherein one or more blazed diffraction grating patterns are arranged as a one-dimensional (1D) array having periodicity in one lateral direction and having diffraction characteristics. (Embodiment 105) The method according to embodiment 104, wherein the 1D array serves as a 1D grating configured to preferentially diffract light in one direction. (Embodiment 106) The method according to any one of embodiments 86-99, wherein one or more blazed diffraction grating patterns are arranged as a two-dimensional (2D) array having periodicity in two lateral directions and having diffraction characteristics. (Embodiment 107) The method according to embodiment 106, wherein the 2D array serves as a 2D grating configured to preferentially diffract light in two directions. (Embodiment 108) The method according to embodiment 106, wherein the 2D array has the same number of diffraction characteristics in two different lateral directions. (Embodiment 109) The method according to any one of embodiments 1-48, wherein the grating substrate has a refractive index greater than 1.9. (Embodiment 110) The method according to any one of embodiments 1-48, wherein the grating substrate is formed from ZrO2, TiO2, SiC, or a Li-based oxide. (Embodiment 111) The method according to any one of embodiments 86-108, wherein the grating substrate has a refractive index greater than 1.9. (Embodiment 112) The method according to any one of embodiments 86-108, wherein the grating substrate is formed from ZrO2, TiO2, SiC, or a Li-based oxide. (Additional Considerations)

[0169] In the foregoing specification, the invention has been described with reference to its specific embodiments. However, it will be apparent that various modifications and changes can be made therein without departing from the broader spirit and scope of the invention. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a limiting sense.

[0170] In fact, the systems and methods of the present disclosure each have several innovative aspects, and it should be understood that none of them alone participate in or are required for the desirable attributes disclosed herein. The various features and processes described above can be used independently of each other or combined in various ways. All possible combinations and sub-combinations are intended to fall within the scope of the present disclosure.

[0171] Certain features described herein in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, the various features described in the context of a single embodiment may also be implemented separately in multiple embodiments or in any suitable sub-combination. Further, features may be described above as acting in a certain combination and may further be claimed as such, but one or more features from the claimed combination may in some cases be deleted from the combination, and the claimed combination may be directed to a sub-combination or a variation of a sub-combination. No single feature or group of features is necessary or essential to every embodiment.

[0172] In particular, conditional clauses used in this specification such as "can", "could", "might", "may", "e.g.", and equivalents are generally intended to convey that while one embodiment includes a certain feature, element, and / or step, another embodiment does not, unless specifically stated otherwise or understood otherwise within the context in which they are used. Thus, such conditional clauses are generally not intended to imply that a feature, element, and / or step is required in any way for one or more embodiments, or that one or more embodiments necessarily include logic for determining whether these features, elements, and / or steps should be included or implemented in any particular embodiment, regardless of the author's input or prompting. The terms "comprising", "including", "having", and equivalents are synonyms and are used inclusively in a non-limiting manner, excluding additional elements, features, acts, operations, etc. Also, the term "or", when used, for example, to connect a list of elements, is used in its inclusive sense (and not in its exclusive sense) such that the term "or" means one, some, or all of the elements in the list. Additionally, the articles "a", "an", and "the" as used in this application and the appended claims should be construed to mean "one or more" or "at least one" unless otherwise defined. Similarly, operations may be depicted in the drawings in a particular order, but it should be recognized that this is not necessary for achieving the desired result, i.e., such operations need not be performed in the particular order shown or in a sequential order, nor is it necessary that all of the illustrated operations be performed. Further, the drawings may schematically depict one or more exemplary processes in the form of flowcharts. However, other operations not depicted may also be incorporated within the exemplary methods and processes schematically illustrated. For example, one or more additional operations may be performed before, after, simultaneously with, or during any of the illustrated operations.In addition, the operations may be rearranged or reordered in other embodiments. In certain situations, multitasking and parallel processing may be advantageous. Further, the separation of various system components in the embodiments described above should not be understood as requiring such separation in all embodiments, and it should be understood that the program components and systems described may generally be integrated together in a single software product or packaged into multiple software products. In addition, other implementations are within the scope of the following claims. In some cases, the actions recited in the claims may be performed in a different order and still achieve desirable results.

[0173] Accordingly, the claims are not intended to be limited to the embodiments shown herein but are to be accorded the widest scope consistent with the disclosure, principles, and novel features disclosed herein.

Claims

1. A method for processing a blazed diffraction grating, The method comprises: providing a master template substrate; imprinting periodically repeated lines on the master template substrate in a plurality of master template regions, wherein the periodically repeated lines in each of the plurality of master template regions extend in a plurality of different radial directions towards a central region of the master template substrate; imprinting at least one blazed diffraction grating pattern on a grating substrate by using at least one of the plurality of master template regions as a master template; transferring a pattern corresponding to the periodically repeated lines into the master template substrate; including transferring the pattern includes dry-etching the master template substrate by using the periodically repeated lines as a partial mask; dry-etching includes locally dry-etching the master template region.

2. The method according to claim 1, wherein the periodically repeated lines in each of the plurality of master template regions extend in a plurality of non-orthogonal directions.

3. The method according to claim 1, wherein imprinting the periodically repeated lines on the master template substrate includes imprinting in at least four master template regions.

4. The method according to claim 1, wherein imprinting the periodically repeated lines includes imprinting across a silicon surface of the master template substrate.

5. Imprinting the periodically repeated lines includes imprinting over the silicon oxide surface of the master template substrate, the method according to claim 1.

6. Imprinting the periodically repeated lines on the master template substrate includes sequentially imprinting in each of the plurality of master template regions using the same primary master template, the method according to claim 1.

7. The periodically repeated lines formed on the master template substrate have a sawtooth profile, the method according to claim 1.

8. The periodically repeated lines formed on the master template substrate comprise symmetric opposing side surfaces that form a similar angle with respect to the plane of the master template substrate, the method according to claim 1.

9. The periodically repeated lines formed on the master template substrate comprise asymmetric opposing side surfaces that form different angles with respect to the plane of the master template substrate, the method according to claim 1.

10. The periodically repeated lines formed on the master template substrate comprise side surfaces having a stepped structure, the method according to claim 1.

11. The periodically repeated lines formed on the master template substrate include a polymer material, the method according to claim 1.

12. The periodically repeated lines formed on the master template substrate include a dielectric material, the method according to claim 1.

13. The method further includes coating the periodically repeated lines formed on the master template substrate with a dielectric material, the method according to claim 1.

14. The method according to claim 1 further includes coating the periodically repeated lines formed on the master template substrate with a metal oxide or a metal nitride.

15. The method according to claim 1 further includes coating the periodically repeated lines formed on the master template substrate with a metal or a metal alloy.

16. Imprinting the periodically repeated lines includes imprinting using a primary master template having periodically repeated lines formed on a primary master substrate, according to the method of claim 1.

17. The method according to claim 1, wherein the plurality of different radial directions are not associated with the crystallographic directions of the master template substrate.

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