Method for preparing two-dimensional coupling-out grating structure, diffractive optical waveguide and augmented reality device

Abstract

The application provides a preparation method of a two-dimensional coupling-out grating structure, a diffractive optical waveguide and an augmented reality device. All characteristic edges of the two-dimensional coupling-out grating structure are disassembled and classified, and then single photolithography and etching are sequentially performed on each type of characteristic edge, so that all characteristic edge patterns are obtained, and finally the two-dimensional coupling-out grating structure is formed. Since each two adjacent and intersecting characteristic edges are disassembled and classified into different photolithography and etching processes, the proximity effect caused by the scattering, backscattering and reflection of high-energy incident electrons at the pattern intersection in the photolithography process is avoided, the fidelity and pattern resolution of the actual manufactured pattern and the design pattern are effectively improved, and the coupling-out efficiency and precision of the diffractive optical waveguide are effectively improved.

Description

Technical Field

[0001] This invention relates to the field of optical imaging technology, and in particular to a method for fabricating a two-dimensional coupled grating structure, a diffractive waveguide, and an augmented reality device. Background Technology

[0002] With the rapid development of semiconductor technology, the interaction between humans and computers is evolving at an unprecedented pace. Augmented Reality (AR) displays offer humans more multidimensional information, and AR technology based on near-eye display devices is currently a hot research topic, attracting widespread attention. The lossless transmission and high penetration of optical waveguide technology effectively ensure the image clarity of glasses, making it considered the mainstream optical solution for consumer-grade AR glasses. Currently, optical waveguides on the market are generally divided into geometric array waveguides and diffractive waveguides. Diffractive waveguides are further divided into volume holographic waveguides and surface relief grating waveguides. The essence of diffractive waveguides is to couple the incident light beam into the waveguide through grating diffraction. Surface relief grating waveguides, with their extremely high design freedom and mass production capabilities brought by nanoimprint processing, have significant advantages among many solutions. The diffraction grating obtained using micro-nano optical structure technology is the core component of a diffractive waveguide.

[0003] Currently, the most common diffraction grating structures on the market are one-dimensional gratings and two-dimensional gratings. Among them, two-dimensional gratings have shown significant advantages in terms of size, weight, manufacturing cost, and display performance. Compared with one-dimensional gratings, two-dimensional gratings applied in augmented reality near-eye display devices also have characteristics such as a larger viewing area and eye movement range, and an infinite focal length. Furthermore, by dividing the two-dimensional grating in the coupling region and optimizing the arrangement of the internal microstructure units of the two-dimensional coupling grating structure according to the functional requirements of different regions and the incident direction of the image beam, a larger field of view and improved coupling efficiency can be obtained.

[0004] Because two-dimensional gratings have an additional feature dimension compared to one-dimensional gratings, the precision requirements for patterning techniques are significantly increased. During photolithography, the scattering, backscattering, and reflection of high-energy incident electrons on the resist and substrate cause proximity effects, resulting in distortion between the actual exposed pattern and the designed pattern, and a decrease in resolution. This phenomenon is particularly pronounced at the corners of intersecting patterns. Furthermore, this proximity effect is further amplified when fabricating high-resolution and complex two-dimensional gratings. Summary of the Invention

[0005] In view of the above problems, the present invention proposes a method for fabricating a two-dimensional coupled grating structure to solve the problems of pattern distortion and resolution reduction caused by proximity effect in photolithography, thereby producing a high-resolution two-dimensional grating that is closer to the design pattern.

[0006] According to a first aspect of the present invention, a method for fabricating a two-dimensional coupling grating structure is provided, the two-dimensional coupling grating structure being configured to diffract and couple an image beam transmitted in an optical waveguide substrate from the optical waveguide substrate; the two-dimensional coupling grating structure includes a plurality of two-dimensional grating units;

[0007] The fabrication method of the two-dimensional coupled grating structure includes:

[0008] All two-dimensional grating units are decomposed into feature edges to obtain L types of feature edges. Any two types of feature edges in the L types of feature edges have an intersection point or their extensions have an intersection point, where L is a positive integer.

[0009] L alignment marks corresponding to overlay are formed on the optical waveguide substrate;

[0010] According to the overlay sequence, the optical waveguide substrate is subjected to the first photolithography and etching according to the alignment mark corresponding to the first type of feature edge to form the pattern of the first type of feature edge on the optical waveguide substrate; this step is repeated until the patterns of the L types of feature edges are all formed to obtain the two-dimensional coupling grating structure on the optical waveguide substrate, where I is a positive integer and I≤L.

[0011] Optionally, along the first direction, the two-dimensional coupling grating structure is divided into N regions, where N is a positive integer and N≥2, and the orientation of the two-dimensional grating units in different regions is different; the first direction is perpendicular to the second direction, and the second direction is the forward direction of the image beam of the optical waveguide substrate;

[0012] The step of decomposing all two-dimensional grating units into feature edges to obtain L types of feature edges includes:

[0013] For all two-dimensional grating units with different orientations in the N regions, feature edges are decomposed. Each pair of adjacent and intersecting feature edges is separated to obtain K feature edges, where K is a positive integer and K≥2N;

[0014] The K feature edge graphs are classified into L categories, where L is a positive integer and L≤K; and parallel feature edges belong to the same category.

[0015] Optionally, the feature edge is a straight edge.

[0016] Optionally, forming alignment marks corresponding to L overlays on the optical waveguide substrate specifically includes:

[0017] The number and position of the corresponding alignment marks are determined based on the graphics of various feature edges;

[0018] The optical waveguide substrate is photolithographically etched and etched using the alignment mark pattern as a mask to form L-fold overlay alignment marks on the optical waveguide substrate.

[0019] Optionally, the alignment mark may be a quadrilateral, a circle, an octagon, a cross, or an array of patterns or combinations thereof.

[0020] Optionally, the step of performing the first photolithography and etching on the optical waveguide substrate according to the alignment marks corresponding to the first type of feature edge in the overlay sequence, so as to form the pattern of the first type of feature edge on the optical waveguide substrate, specifically includes:

[0021] Photoresist is formed on the optical waveguide substrate;

[0022] According to the overlay sequence, align the photolithographic pattern corresponding to the feature edge pattern of type I with the corresponding alignment mark;

[0023] Photolithography is performed based on the photolithographic pattern corresponding to the feature edge pattern of type I, and the pattern on the corresponding photolithographic pattern is transferred to the photoresist to form a patterned photoresist.

[0024] The optical waveguide substrate is etched using the patterned photoresist as a mask to form a type I feature edge pattern on the optical waveguide substrate.

[0025] Optionally, the photolithography is electron beam lithography, and the etching includes CCP, ICP, or IBE.

[0026] Optionally, the material of the optical waveguide substrate includes any one of Si, SiO2 or Si3N4, or a coating with a metal and its oxide is formed on any of the aforementioned materials.

[0027] According to a second aspect of the present invention, a diffractive optical waveguide is provided, comprising the two-dimensional coupling grating structure described in the first aspect of the present invention.

[0028] According to a third aspect of the present invention, an augmented reality device is also provided, comprising the two-dimensional coupling grating structure described in the first aspect of the present invention, or the diffractive waveguide described in the second aspect of the present invention.

[0029] The method for fabricating a two-dimensional coupled grating structure provided by this invention involves disassembling and classifying all feature edges of the two-dimensional grating unit of the two-dimensional coupled grating structure. Each pair of adjacent and intersecting feature edges is separated, and parallel feature edges are grouped into the same category. Then, each category of feature edges is sequentially subjected to individual photolithography and etching to obtain all feature edge patterns, forming the final two-dimensional coupled grating structure. Because each pair of adjacent and intersecting feature edges is disassembled and classified into different photolithography and etching processes, the proximity effect caused by scattering, backscattering, and reflection of high-energy incident electrons at pattern intersections during photolithography is avoided. This effectively improves the fidelity and resolution of the actual fabricated pattern compared to the designed pattern, thereby effectively improving the coupling efficiency and accuracy of the diffractive waveguide. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a schematic flowchart of a method for fabricating a two-dimensional coupled grating structure according to an embodiment of the present invention;

[0032] Figure 2A This is a schematic diagram of the layout of a diffractive waveguide provided in an embodiment of the present invention;

[0033] Figure 2B This is a schematic diagram of the arrangement of two-dimensional grating units of a two-dimensional coupling grating for a diffractive waveguide according to an embodiment of the present invention;

[0034] Figures 3A-3B This is a schematic diagram illustrating the disassembly and classification of feature edges of a two-dimensional coupled grating unit according to an embodiment of the present invention;

[0035] Figures 4A-4F This is a top view schematic diagram of different process stages of the fabrication process of a two-dimensional coupled grating structure provided in an embodiment of the present invention.

[0036] Explanation of reference numerals in the attached figures:

[0037] K1~K17 - Feature edges of two-dimensional grating units;

[0038] L1~L4 - The categories of feature edges of two-dimensional grating units;

[0039] ①~⑧ - Overlay alignment marks. Detailed Implementation

[0040] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] The terms “first,” “second,” “third,” “fourth,” etc. (if present) in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms “comprising” and “having,” and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0042] In view of the fact that in the traditional two-dimensional grating fabrication process, the proximity effect caused by the scattering, backscattering, and reflection of high-energy incident electrons on the resist and substrate during photolithography can cause distortion between the actual exposed pattern and the designed pattern, resulting in a decrease in resolution, and this phenomenon is particularly obvious at the corners of the intersecting patterns, and is further amplified when fabricating high-resolution and complex two-dimensional gratings, this invention proposes a method for fabricating a two-dimensional coupled grating structure. By disassembling and classifying all feature edges of two-dimensional grating units facing different directions in different regions of the two-dimensional coupled grating structure, each pair of adjacent and intersecting feature edges is separated, and parallel feature edges are grouped into the same category. Then, each category of feature edges is sequentially photolithographically and etched individually to obtain all feature edge patterns and form the final two-dimensional coupled grating structure. By decomposing and classifying each pair of adjacent and intersecting feature edges into different lithography and etching processes, the proximity effect caused by scattering, backscattering, and reflection of high-energy incident electrons at pattern intersections during lithography is avoided. This effectively improves the fidelity and resolution of the actual fabricated pattern and the designed pattern, thereby effectively improving the coupling efficiency and accuracy of the diffractive waveguide.

[0043] The technical solution of the present invention will be described in detail below with reference to specific embodiments. Concepts or processes that are the same or similar may not be repeated in some embodiments.

[0044] A schematic diagram of the layout of the diffractive waveguide provided in a specific embodiment of the present invention is shown below. Figure 2A As shown, the coupling region grating structure of the diffractive waveguide is a two-dimensional coupling grating structure, which is divided into two regions along the Y direction. Each region includes multiple two-dimensional grating units, and the two grating units in the two regions are oriented differently. The Y direction is perpendicular to the X direction, which is the direction of propagation of the image beam from the waveguide substrate. The two-dimensional coupling grating structure is configured to diffract and couple the image beam transmitted in the waveguide substrate out of the waveguide substrate. It should be understood that this invention is not limited thereto, and other layouts of the coupling region of the diffractive waveguide and other arrangements of the grating units corresponding to the two-dimensional coupling grating structure are also within the scope of protection of this invention.

[0045] Please refer to Figure 1 , Figure 2A-2B and combined Figures 4A-4F The fabrication method of the two-dimensional coupling grating structure provided in one embodiment of the present invention includes S1-S4, as follows:

[0046] S1: Decompose all two-dimensional grating units into feature edges to obtain L types of feature edges. Any two types of feature edges in L types have an intersection point or their extensions have an intersection point, where L is a positive integer.

[0047] Taking the fabrication of a two-dimensional coupling grating structure in a diffractive waveguide provided in one embodiment of the present invention as an example, S1 may specifically include the following steps S11-S12:

[0048] S11: Decompose the characteristic edges of all two-dimensional grating units with different orientations in the two regions of the diffraction waveguide coupling area. Separate each pair of adjacent and intersecting characteristic edges to obtain 17 characteristic edges from K1 to K17. Figure 2A As shown.

[0049] In one preferred embodiment, all feature edges are straight edges; however, the present invention is not limited thereto, and other forms of feature edges are also within the scope of protection of the present invention.

[0050] S12: The 17 feature edges extracted are classified into categories, and parallel feature edges are grouped into the same category, resulting in four categories of feature edges, L1 to L4. Any two feature edges in the four categories have an intersection point or their extensions have an intersection point. The fabrication of each type of feature edge graphic is completed in an independent overlay process, requiring a total of four independent overlay processes. This changes the fabrication of each pair of adjacent and intersecting feature edges in the original two-dimensional coupled grating structure from being completed in a single overlay process to being completed in different overlay processes. This avoids the proximity effect caused by the scattering, backscattering, and reflection of high-energy incident electrons at the intersection of two-dimensional graphics during the photolithography process of a single overlay process, thereby effectively improving the fidelity and resolution of the actual fabricated graphics and the designed graphics.

[0051] As a preferred implementation, the classification of feature edges should be minimized while ensuring graphic resolution, so as to reduce the number of overlay processes, reduce the overlay error introduced between different overlay processes, and thus further improve the fidelity of the actual produced graphics and the designed graphics.

[0052] S2: Form alignment marks corresponding to L overlays on the optical waveguide substrate.

[0053] Taking the fabrication of a two-dimensional coupling grating structure in a diffractive waveguide provided in one embodiment of the present invention as an example, S2 may specifically include the following steps S21-S22:

[0054] S21: Determine the number and position of the corresponding alignment marks based on the graph of the feature edges of types L1 to L4.

[0055] For each overlay process, in order to meet the overlay alignment accuracy requirements, at least two overlay alignment marks are required for each overlay. Generally, the alignment marks are set at positions that are far apart on both sides of the overlay pattern. According to the overlay alignment accuracy requirements, the more overlay alignment marks, the better. The specific number of overlay alignment marks depends on the accuracy requirements of the lithography equipment and the complexity of the overlay pattern.

[0056] The graphics of the alignment marks can include any one or a combination of quadrilaterals, circles, octagons, crosses, or arrayed graphics.

[0057] In one embodiment of the present invention, corresponding to the feature edge graphics of types L1 to L4, eight overlay alignment marks are set as ① to ⑧, and their positions are distributed as follows: Figure 4AAs shown, the alignment mark graphic is selected as a cross shape. The overlay process for each type of feature edge graphic corresponds to four overlay alignment marks, where ①③->⑧④ corresponds to the overlay process for the L1 type of feature edge graphic, ②⑦->③⑥ corresponds to the overlay process for the L2 type of feature edge graphic, ②⑤->⑧⑥ corresponds to the overlay process for the L3 type of feature edge graphic, and ⑦④->⑥⑤ corresponds to the overlay process for the L4 type of feature edge graphic. Of course, it should be understood that this invention is not limited thereto, and other overlay alignment mark graphics, quantities, and arrangements are also within the scope of protection of this invention.

[0058] S22: Photolithography and etching are performed on the optical waveguide substrate using the mask of the alignment mark pattern as a mask to form L-fold overlay alignment marks on the optical waveguide substrate.

[0059] In one embodiment of the present invention, alignment marks ① to ⑧ corresponding to the four overlay processes of L1 to L4 are finally formed on the optical waveguide substrate, such as... Figure 4A As shown.

[0060] S3: According to the overlay sequence, the optical waveguide substrate is subjected to the first photolithography and etching according to the alignment mark corresponding to the first type of feature edge, so as to form the pattern of the first type of feature edge on the optical waveguide substrate.

[0061] Taking the fabrication of a two-dimensional coupling grating structure in a diffractive waveguide provided in one embodiment of the present invention as an example, S3 may specifically include the following steps S31-S33:

[0062] S31: Photoresist is formed on the optical waveguide substrate.

[0063] S32: According to the overlay sequence, align the photolithographic pattern corresponding to the L1 type feature edge pattern with the corresponding alignment marks ①③->⑧④.

[0064] S33: Perform photolithography according to the photolithography pattern corresponding to the feature edge pattern of the L1 group, and transfer the pattern on the corresponding photolithography pattern to the photoresist to form a patterned photoresist;

[0065] In one specific embodiment, the photolithography process is ultraviolet lithography, the photolithographic pattern corresponding to the L1 type feature edge pattern is the pattern on the photomask, and the pattern on the photomask is provided with alignment marks.

[0066] In a preferred embodiment, the photolithography process is electron beam lithography, and the photolithographic pattern corresponding to the L1 type feature edge pattern is an electron beam direct-write pattern, which contains alignment marks. Compared with ultraviolet lithography, electron beam lithography has a shorter wavelength and higher resolution, which can further improve the fidelity and resolution of the actual fabricated two-dimensional coupled grating structure pattern and the designed pattern.

[0067] Of course, it should be understood that the present invention is not limited thereto, and other photolithography methods are also within the scope of protection of the present invention.

[0068] S34: The optical waveguide substrate is etched using patterned photoresist as a mask to form the L1 group of feature edge patterns on the optical waveguide substrate, such as... Figure 4B As shown.

[0069] In specific embodiments, etching can be CCP, ICP, or IBE etching. Of course, it should be understood that the present invention is not limited thereto, and other etching methods are also within the scope of protection of the present invention.

[0070] S4: Repeat step S3 until all the L-type feature edges are formed to obtain a two-dimensional coupled grating structure on the optical waveguide substrate, where I is a positive integer and I≤L.

[0071] In a specific embodiment, steps S31 to S34 are repeated, and photolithography and etching are performed sequentially according to the alignment marks ②⑦->③⑥, ②⑤->⑧⑥, and ⑦④->⑥⑤ to form L2 to L4 type feature edge patterns on the optical waveguide substrate, respectively. Figures 4C-4E As shown, the L1 to L4 type feature edge patterns together form the final two-dimensional coupled grating structure, as follows: Figure 4F As shown.

[0072] As an example, the material of the optical waveguide substrate includes any one of Si, SiO2, or Si3N4, or a coating with a metal and its oxide formed on any of the foregoing. Of course, it should be understood that the present invention is not limited thereto, and other optical waveguide substrate materials are also within the scope of protection of the present invention.

[0073] According to one embodiment of the present invention, a diffractive waveguide is also provided, wherein the two-dimensional coupling grating structure of the coupling region of the diffractive waveguide is prepared by the preparation method of the above-described specific embodiment.

[0074] In a specific example, such as Figure 2AAs shown, the coupling region grating structure of the diffractive waveguide is a two-dimensional coupling grating structure, which is divided into two regions along the Y direction. Each region includes multiple two-dimensional grating units, and the two regions have different orientations. The Y direction is perpendicular to the X direction, which is the direction of the image beam propagating from the waveguide substrate. The two-dimensional coupling grating structure is configured to diffract and couple the image beam transmitted in the waveguide substrate out of the waveguide substrate. The two-dimensional coupling grating structure in the coupling region is prepared by the fabrication method of the two-dimensional coupling grating structure in the above specific embodiment. During the fabrication process, the feature edges of each pair of adjacent and intersecting two-dimensional coupling grating patterns are decomposed and classified into different photolithography and etching processes. This avoids the proximity effect caused by scattering, backscattering, and reflection of high-energy incident electrons at the pattern intersections during photolithography, effectively improving the fidelity and resolution of the actual fabricated pattern and the designed pattern, thereby effectively improving the coupling efficiency and accuracy of the diffractive waveguide. Of course, it should be understood that the present invention is not limited thereto. Other layouts of the coupling region of the diffractive waveguide prepared by the method for preparing the two-dimensional coupling grating structure according to the present invention, as well as other arrangements of the grating units corresponding to the two-dimensional coupling grating, are also within the scope of protection of the present invention.

[0075] In addition, the present invention provides an augmented reality device, including the two-dimensional coupled grating structure involved in the above embodiments, or including the diffractive waveguide involved in the above embodiments.

[0076] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for fabricating a two-dimensional coupled grating structure, characterized in that, The two-dimensional coupling grating structure is configured to diffract and couple an image beam transmitted in an optical waveguide substrate out of the optical waveguide substrate; the two-dimensional coupling grating structure includes a plurality of two-dimensional grating units; The fabrication method of the two-dimensional coupled grating structure includes: All two-dimensional grating units are decomposed into feature edges to obtain L types of feature edges. Any two types of feature edges in the L types of feature edges have an intersection point or their extension lines have an intersection point, where L is a positive integer. L alignment marks corresponding to overlay are formed on the optical waveguide substrate; According to the overlay sequence, the optical waveguide substrate is subjected to the first photolithography and etching according to the alignment mark corresponding to the first type of feature edge to form the pattern of the first type of feature edge on the optical waveguide substrate; this step is repeated until the patterns of the L types of feature edges are all formed to obtain the two-dimensional coupling grating structure on the optical waveguide substrate, wherein the photolithography process is ultraviolet lithography or electron beam lithography, I is a positive integer, and I≤L.

2. The method for fabricating the two-dimensional coupled grating structure according to claim 1, characterized in that, Along the first direction, the two-dimensional coupling grating structure is divided into N regions, where N is a positive integer and N≥2, and the orientation of the two-dimensional grating units in different regions is different; the first direction is perpendicular to the second direction, and the second direction is the forward direction of the image beam of the optical waveguide substrate; The step of decomposing all two-dimensional grating units into feature edges to obtain L types of feature edges includes: For all two-dimensional grating units with different orientations in the N regions, feature edges are decomposed. Each pair of adjacent and intersecting feature edges is separated to obtain K feature edges, where K is a positive integer and K≥2N; The K feature edge graphs are classified into L categories, where L is a positive integer and L≤K; and parallel feature edges belong to the same category.

3. The method for fabricating the two-dimensional coupled grating structure according to claim 1, characterized in that, The feature edge is a straight edge.

4. The method for fabricating the two-dimensional coupled grating structure according to claim 1, characterized in that, The process of forming alignment marks corresponding to L overlays on the optical waveguide substrate specifically includes: The number and position of the corresponding alignment marks are determined based on the graphics of various feature edges; The optical waveguide substrate is photolithographically etched and etched using the alignment mark pattern as a mask to form L-fold overlay alignment marks on the optical waveguide substrate.

5. The method for fabricating a two-dimensional coupled grating structure according to claim 1, characterized in that, The alignment mark graphic includes any one or a combination of quadrilaterals, circles, octagons, crosses, or arrayed graphic combinations.

6. The method for fabricating a two-dimensional coupled grating structure according to claim 1, characterized in that, The first step involves performing photolithography and etching on the optical waveguide substrate according to the alignment marks corresponding to the first type of feature edge, following the overlay sequence, to form a pattern of the first type of feature edge on the optical waveguide substrate. Specifically, this includes: Photoresist is formed on the optical waveguide substrate; According to the overlay sequence, align the photolithographic pattern corresponding to the feature edge pattern of type I with the corresponding alignment mark; Photolithography is performed based on the photolithographic pattern corresponding to the feature edge pattern of type I, and the pattern on the corresponding photolithographic pattern is transferred to the photoresist to form a patterned photoresist. The optical waveguide substrate is etched using the patterned photoresist as a mask to form a type I feature edge pattern on the optical waveguide substrate.

7. The method for fabricating a two-dimensional coupled grating structure according to any one of claims 1-6, characterized in that, The photolithography is electron beam lithography, and the etching includes CCP, ICP, or IBE.

8. The method for fabricating a two-dimensional coupled grating structure according to any one of claims 1-6, characterized in that, The material of the optical waveguide substrate includes any one of Si, SiO2 or Si3N4, or a coating with a metal and its oxide is formed on any of the aforementioned materials.

9. A diffractive optical waveguide, characterized in that, include: The two-dimensional coupled grating structure as described in any one of claims 1 to 8.

10. An augmented reality device, characterized in that, include: The two-dimensional coupling grating structure as described in any one of claims 1 to 8, or the diffractive waveguide as described in claim 9.

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