Diffractive optical waveguide

Abstract

The utility model discloses a kind of diffractive optical waveguide, the diffractive optical waveguide includes: optical waveguide substrate and low fold glue layer, low fold glue layer covers on the one side surface of optical waveguide substrate and is provided with micro-nano structure area;Protective layer, cover the one side surface of low fold glue layer and deviate from optical waveguide substrate;Protective layer includes center protective sheet and annular protective frame;Annular protective frame surrounds the orthographic projection of center protective sheet in the plane of optical waveguide substrate in the orthographic projection of the plane of optical waveguide substrate, and with the orthographic projection edge of center protective sheet in the plane of optical waveguide substrate is adjacent to;Micro-nano structure area is located in the orthographic projection of center protective sheet in the plane of optical waveguide substrate.The utility model not only can utilize center protective sheet to protect micro-nano structure area, also can pass through annular protective frame, on one hand avoid protective sheet and outer frame collision to cause damage, on the other hand cover step area, block water vapor into low fold glue layer, further improve the reliability and service life of diffractive optical waveguide.

Description

Technical Field

[0001] This utility model relates to the field of optical waveguide technology, and in particular to a diffractive optical waveguide. Background Technology

[0002] As a core optical component of augmented reality (AR) or virtual reality (VR) devices, diffractive waveguides require appropriate structures to protect the micro- and nano-structures on the waveguide substrate, such as grating structures.

[0003] In current diffractive waveguides, a low-refractive-index adhesive layer is coated on one side of the waveguide substrate with micro / nano-structured regions. A protective sheet is then placed over the low-refractive-index adhesive layer to protect the micro / nano-structures. Furthermore, the size of this protective sheet is slightly smaller than the waveguide substrate and the low-refractive-index adhesive layer, with its edges relatively recessed, thus forming a stepped structure. This structure exposes the surface of the low-refractive-index adhesive layer's edge region, making it easier for external moisture to penetrate into the low-refractive-index adhesive layer, causing problems such as delamination at the low-refractive-index adhesive layer interface and deterioration of optical performance. Utility Model Content

[0004] This invention provides a diffractive waveguide to protect and seal the stepped surface between the protective sheet and the low-refractive adhesive layer, preventing moisture from penetrating into the low-refractive adhesive layer, while also protecting the protective sheet during bending tests.

[0005] In a first aspect, embodiments of the present invention provide a diffractive optical waveguide, comprising:

[0006] An optical waveguide substrate, wherein at least one side surface of the optical waveguide substrate is provided with at least one micro / nano structure region;

[0007] A low-refractive-index adhesive layer, which covers one side surface of the optical waveguide substrate where the micro / nano structure region is provided;

[0008] A protective layer covers the side surface of the low-refractive adhesive layer facing away from the optical waveguide substrate; the protective layer includes a central protective sheet and an annular protective frame; the orthographic projection of the annular protective frame onto the plane where the optical waveguide substrate is located surrounds the orthographic projection of the central protective sheet onto the plane where the optical waveguide substrate is located, and is adjacent to the edge of the orthographic projection of the central protective sheet onto the plane where the optical waveguide substrate is located; the micro / nano structure region is located in the orthographic projection of the central protective sheet onto the plane where the optical waveguide substrate is located.

[0009] Optionally, the width of the annular protective frame is D, and the distance between the side surface of the low-fold adhesive layer away from the optical waveguide substrate and the side surface of the central protective sheet away from the low-fold adhesive layer is L, where D1=L / K, 1.5≤K≤1.8.

[0010] Optionally, the surface of the annular protective frame facing away from the low-fold adhesive layer is flush with the surface of the central protective sheet facing away from the low-fold adhesive layer, and the edge of the annular protective frame away from the central protective sheet is flush with the edge of the low-fold adhesive layer.

[0011] Optionally, the protective layer further includes an optical adhesive layer; the optical adhesive layer is located between the central protective sheet and the low-refractive adhesive layer; the orthographic projection of the optical adhesive layer onto the plane of the optical waveguide substrate coincides with the orthographic projection of the central protective sheet onto the plane of the optical waveguide substrate.

[0012] Optionally, the annular protective frame is integrally connected to the low-fold adhesive layer.

[0013] Optionally, a micro-nano structure is provided in the micro-nano structure region, and the thickness D2 of the low-fold adhesive layer is 1 to 3.5 times the height H of the micro-nano structure.

[0014] Optionally, the optical waveguide substrate includes a glass substrate and a high-refractive-index adhesive layer located on one side surface of the glass substrate. The high-refractive-index adhesive layer has a micro / nano structure formed on the side surface of the high-refractive-index adhesive layer opposite to the glass substrate, and a low-refractive-index adhesive layer covers the side surface of the high-refractive-index adhesive layer opposite to the glass substrate.

[0015] Optionally, the at least one micro / nanostructure region includes an integrated micro / nanostructure region having a two-dimensional micro / nanostructure.

[0016] Alternatively, the at least one micro / nano structure region includes a coupling-in region and a coupling-out region, wherein the coupling-in region and the coupling-out region have a one-dimensional micro / nano structure or a two-dimensional micro / nano structure.

[0017] Alternatively, the at least one micro / nano structure region includes an introducing region, a transition region, and an outtroducing region, wherein the introducing region, the transition region, and the outtroducing region have a one-dimensional micro / nano structure or a two-dimensional micro / nano structure.

[0018] Optionally, the annular protective frame has waterproof and UV-resistant functions.

[0019] Optionally, it also includes an ink layer coated on the sidewalls of the optical waveguide substrate, the low-refractive adhesive layer, and the annular protective frame.

[0020] The diffractive waveguide provided in this embodiment of the invention features a protective layer covering a stacked waveguide substrate and a low-refractive-index adhesive layer. This protective layer is essentially composed of a central protective sheet and an annular protective frame surrounding the central protective sheet. The central protective sheet not only protects the micro / nano structure region of the waveguide, but the annular protective frame also prevents damage to the protective sheet from collisions with the outer frame when the waveguide is surrounded, thus improving the reliability of the diffractive waveguide. Furthermore, the protective frame covers the stepped area formed by the edges of the low-refractive-index adhesive layer and the central protective sheet, protecting the surface of the low-refractive-index adhesive layer's edge region and preventing moisture from easily entering the low-refractive-index adhesive layer, further improving the reliability and lifespan of the diffractive waveguide. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of a diffractive optical waveguide in related technologies;

[0022] Figure 2 This is a schematic diagram of the structure of a diffractive optical waveguide provided in an embodiment of this utility model;

[0023] Figure 3 This is a flowchart illustrating the preparation process of a ring-shaped protective frame according to an embodiment of the present invention;

[0024] Figure 4 This is a schematic diagram of another diffractive waveguide structure provided in this embodiment of the present invention;

[0025] Figure 5 This is a schematic diagram of another diffractive waveguide provided in this embodiment of the present invention;

[0026] Figure 6 This is a top view of a diffractive optical waveguide provided in an embodiment of the present invention;

[0027] Figure 7 This is a schematic diagram of another diffractive waveguide provided in this embodiment of the present invention. Detailed Implementation

[0028] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, not the entire structure.

[0029] The terminology used in the embodiments of this utility model is for the purpose of describing specific embodiments only and is not intended to limit the utility model. It should be noted that directional terms such as "upper," "lower," "left," and "right" described in the embodiments of this utility model are used to describe the angles shown in the accompanying drawings and should not be construed as limiting the embodiments of this utility model. Furthermore, in the context, it should be understood that when referring to an element being formed "upper" or "lower" of another element, it can be formed not only directly "upper" or "lower" of the other element, but also indirectly "upper" or "lower" of the other element through an intermediate element. The terms "first," "second," etc., are used for descriptive purposes only and do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0030] The term "comprising" and its variations as used in this utility model are open-ended, meaning "including but not limited to". The term "based on" means "at least partially based on". The term "one embodiment" means "at least one embodiment".

[0031] It should be noted that the concepts of "first" and "second" mentioned in this utility model are only used to distinguish the corresponding contents and are not used to limit the order or interdependence.

[0032] It should be noted that the terms "a" and "a plurality of" used in this utility model are illustrative rather than restrictive. Those skilled in the art should understand that, unless otherwise expressly indicated in the context, they should be understood as "one or more".

[0033] Figure 1 This is a schematic diagram of a diffractive optical waveguide structure in related technologies. (Reference) Figure 1 As described in the background section, currently, diffractive waveguides typically employ a fully laminated process. A low-refractive-index adhesive layer 12' is coated on one side of the waveguide substrate 11' with the micro / nano structure 101', and then the low-refractive-index adhesive layer 12' is bonded to the protective sheet 21' through an optically clear adhesive (OCA) layer 22' to protect the micro / nano structure.

[0034] Furthermore, in related technologies, the dimensions of the OCA adhesive layer 22' and the protective sheet 21' are usually set smaller than the dimensions of the optical waveguide substrate 11'. The reason for this design is that in the automated packaging process, the optical waveguide substrate 11' has positioning marks (not shown in the figure) which will serve as a reference for positioning the protective sheet 21'. If the dimensions of the protective sheet 21' and the OCA adhesive layer 22' are greater than or equal to the dimensions of the optical waveguide substrate 11', they will block the positioning marks on the optical waveguide substrate 11', thereby affecting the positioning accuracy of the protective sheet 21'.

[0035] However, this shape design presents the following problems: 1. Since the edges of the OCA adhesive layer 22' and the protective sheet 21' are located inside the low-reflection adhesive layer 12', the protective sheet 21', the OCA adhesive layer 22', and the low-reflection adhesive layer 12' form a stepped structure (as shown in the dotted box A in the figure). Furthermore, the ink layer 40' formed by the ink adhesive material in the ink coating process has poor water resistance, making it easy for moisture in the environment to penetrate along these stepped edges and gradually seep into the low-reflection adhesive layer 12'. This penetration not only reduces the bonding strength of the low-reflection adhesive layer 12' but may also cause interface delamination and deterioration of optical performance. 2. In the full lamination process, the protective sheet 21' is usually made of thin glass. During the three-point bending test, the protective sheet 21' is easily damaged due to collisions with the edge of the product frame (e.g., the frame 30').

[0036] To address the aforementioned technical problems, this utility model provides a diffractive optical waveguide. Figure 2 This is a schematic diagram of a diffractive waveguide provided in an embodiment of the present invention. (Refer to...) Figure 2 The diffractive waveguide includes a waveguide substrate 11, a low-refractive-index adhesive layer 12, and a protective layer 20. At least one micro / nano structure region 100 is formed on at least one side surface of the waveguide substrate 11. The low-refractive-index adhesive layer 12 covers the side surface of the waveguide substrate 11 where the micro / nano structure region 100 is formed. The protective layer 20 covers the side surface of the low-refractive-index adhesive layer 12 facing away from the waveguide substrate 11. The protective layer 20 includes a central protective sheet 21 and an annular protective frame 23. The orthographic projection of the annular protective frame 23 onto the plane of the waveguide substrate 11 surrounds the orthographic projection of the central protective sheet 21 onto the plane of the waveguide substrate 11 and is adjacent to the edge of the orthographic projection of the central protective sheet 21 onto the plane of the waveguide substrate 11. The micro / nano structure region 100 is located in the orthographic projection of the central protective sheet 21 onto the plane of the waveguide substrate 11.

[0037] A diffractive waveguide can be understood as a product structure that, based on the waveguide principle, uses geometric or diffractive optical structures to extend an image generated by a tiny optomechanical system to cover the field of view of the human eye, thereby achieving image transmission and viewing functions. In practical applications, the waveguide substrate 11 needs to be encapsulated and protected to prevent external influences on its internal optical performance. Those skilled in the art will understand that the waveguide substrate 11 needs to have a micro / nano structure region 100, within which tiny micro / nano structures 101 are provided to guide light wave propagation and achieve the waveguide function. The material of the waveguide substrate 11 can specifically be glass, resin, silicon carbide, zinc sulfide, silicon nitride, or lithium niobate.

[0038] The refractive index of the low-refractive-index adhesive can be set between 1.1 and 1.5. The main function of the low-refractive-index adhesive layer 12 is to reduce light loss during propagation by lowering the refractive index, thereby optimizing light transmission and emission, improving the efficiency of the optical waveguide, and reducing optical loss. Figure 2 As shown, a micro / nano structure 101 is disposed in the micro / nano structure region 100, and the thickness D2 of the low-refractive-index adhesive layer 12 is 1 to 3.5 times the height H of the micro / nano structure 101. Under this condition, the low-refractive-index adhesive layer 12 is relatively high compared to the micro / nano structure 101, which can ensure the coverage of the micro / nano structure 101, buffer the stress caused by external impact, effectively prevent the protective sheet from squeezing the micro / nano structure region 100, protect the micro / nano structure, and reduce the overall thickness of the diffractive waveguide.

[0039] In this embodiment, by covering the optical waveguide substrate with a protective layer 20, which is essentially composed of a central protective sheet 21 and an annular protective frame 23 surrounding the central protective sheet 21, the central protective sheet 21 can protect the micro-nano structure region 100 of the optical waveguide substrate 11. Furthermore, the annular protective frame 23 can prevent damage to the protective sheet caused by collision between the protective sheet and the outer frame when the diffractive optical waveguide is surrounded, thereby improving the reliability of the diffractive optical waveguide. On the other hand, it covers the step area formed by the low-refractive adhesive layer 12 and the edge of the central protective sheet 21, protecting the surface of the edge region of the low-refractive adhesive layer 12, making it difficult for moisture in the environment to enter the low-refractive adhesive layer 12, further improving the reliability and service life of the diffractive optical waveguide.

[0040] The protective sheet can be ultra-thin flexible glass (UTG), and the ring-shaped protective frame 23 can be made of a waterproof material, such as polyurethane or silicone rubber with high cross-linking density, or it can be an adhesive with waterproof and UV-resistant functions, such as silicone rubber or acrylate doped with UV absorbers.

[0041] In relation to the diffractive waveguide provided in this embodiment, this embodiment also provides a specific method for preparing the annular protective frame therein. Figure 3 This is a flowchart illustrating the fabrication process of a ring-shaped protective frame according to an embodiment of this utility model. (Refer to...) Figure 2 and Figure 3 Specifically, firstly, after forming a low-refractive-index resist layer 12 on the optical waveguide substrate 11, an etched layer 230 and a photoresist layer 50 are sequentially formed on the surface of the low-refractive-index resist layer 12. The etched layer 230 is used to form an annular protective frame 23 through etching. Then, through an exposure and development process, the photoresist layer 50 can be patterned to form a photoresist mask 51 with a preset pattern. Afterward, the etched layer 230 is etched using the photoresist mask 51 to remove the area not protected by the photoresist mask 51, and the remaining structure is the annular protective frame 23. Finally, the photoresist mask 51 can be removed by cleaning.

[0042] As described above, the annular protective frame 23 can be fabricated using photolithography. Alternatively, it can be formed by dispensing or printing. Specifically, by dispensing or printing, a ring of adhesive is formed on the surface of the low-fold adhesive layer 12, with the adhesive layer positioned along the edge of the protective sheet. After curing, the adhesive layer forms the annular protective frame.

[0043] Continue to refer to Figure 2 Specifically, an annular side frame 30 can be provided around the aforementioned diffractive waveguide. The waveguide substrate 11, the low-refractive adhesive layer 12, and the protective layer 20 form a stacked structure, with the edges of the stacked structure fitted and fixed within the annular side frame 30. The annular side frame 30 can be understood as a rigid frame or similar structure, mainly used to support and protect the diffractive waveguide.

[0044] In addition, the diffractive waveguide may also include an ink layer 40, which is coated on the sidewalls of the waveguide substrate 11, the low-refractive adhesive layer 12, and the annular protective frame 30. The ink layer 40, covering the sidewalls of the waveguide substrate 11, the low-refractive adhesive layer 12, and the annular protective frame 30, to a certain extent prevents moisture from penetrating through the sides and affecting its optical performance, thus serving a sealing and waterproof function.

[0045] Optionally, the width of the annular protective frame 23 is D1, and the distance between the side surface of the low-fold adhesive layer 12 away from the optical waveguide substrate 11 and the side surface of the central protective sheet 21 away from the low-fold adhesive layer 12 is L, where D1=L / K, 1.5≤K≤1.8.

[0046] Continue to refer to Figure 2 It is understood that the annular protective frame 23 is circular and extends around the central protective sheet 22. It has a certain width in the vertical extension direction to ensure coverage of the edge area of ​​the low-refractive adhesive layer 12. This width is D1. By reasonably setting the thickness of the annular protective frame 23 relative to the low-refractive adhesive layer 12 to meet the above conditions, it can ensure that moisture does not easily enter the low-refractive adhesive layer 12. On the other hand, it can also fix the outer frame of the product, i.e., the annular side frame 30, to the annular protective frame 23, reducing the damage caused by the contact between the diffractive waveguide outer frame and the protective sheet.

[0047] Figure 4 This is a schematic diagram of another diffractive waveguide structure provided in this embodiment of the present invention, for reference. Figure 4 In a preferred embodiment, the surface of the annular protective frame 23 facing away from the low-fold adhesive layer 12 may be flush with the surface of the central protective sheet 21 facing away from the low-fold adhesive layer 12, and the edge of the annular protective frame 23 away from the central protective sheet 21 may be flush with the edge of the low-fold adhesive layer 12.

[0048] In this embodiment, the height of the annular protective frame 23 is set to be flush with the central protective piece 21, and the outer edge of the annular protective frame 23 is flush with the outer edge of the low-fold adhesive layer 12. This avoids a height difference between the upper and side surfaces of the annular protective frame 23, preventing the formation of steps and thus reducing the probability of moisture intruding into the interior from the stepped surface. (Continue to refer to...) Figure 2 and Figure 4 Optionally, the protective layer 20 further includes an optical adhesive layer 22; the optical adhesive layer 22 is located between the central protective sheet 21 and the low-fold adhesive layer 12; the orthographic projection of the optical adhesive layer 22 onto the plane of the optical waveguide substrate 11 coincides with the orthographic projection of the central protective sheet 21 onto the plane of the optical waveguide substrate 11.

[0049] Specifically, the optical adhesive layer 22 can be OCA optical adhesive or liquid optical adhesive, i.e., OCR optical adhesive; there is no limitation here. The optical adhesive layer 22 is mainly responsible for bonding the central protective sheet 21 to the optical waveguide substrate 11 and the low-refractive-index adhesive layer 12. The coverage area of ​​the optical adhesive layer 22 is the same as that of the central protective sheet 21. The optical adhesive layer 22 has good light transmittance and will not affect light transmission or interfere with the user's vision. This embodiment essentially matches the dimensions of the optical adhesive layer 22 with the underlying optical waveguide substrate 11 and low-refractive-index adhesive layer 12, thereby ensuring more uniform stress on the adhesive layer and helping to maintain a uniform refractive index throughout the effective area, ensuring consistent light transmission.

[0050] Figure 5 This is a schematic diagram of another diffractive waveguide structure provided in this embodiment of the present invention, for reference. Figure 5 In another optional embodiment, the optical waveguide substrate 11 may include a glass substrate 111 and a high-refractive-index adhesive layer 112 located on one side surface of the glass substrate 111. A micro / nano structure 101 is formed on the side surface of the high-refractive-index adhesive layer 112 facing away from the glass substrate 111, and a low-refractive-index adhesive layer 12 covers the side surface of the high-refractive-index adhesive layer 112 facing away from the glass substrate 111. The high-refractive-index adhesive layer 112 has a refractive index greater than 1.9, and may specifically be an optically transparent adhesive containing titanium dioxide particles, a zirconia-containing optically transparent adhesive, or a zinc sulfide-containing optically transparent adhesive.

[0051] In a specific embodiment of this utility model, optionally, at least one micro / nano structure region includes an integrated micro / nano structure region having a two-dimensional micro / nano structure; or, at least one micro / nano structure region includes an insertion region and an exit region having a one-dimensional micro / nano structure or a two-dimensional micro / nano structure; or, at least one micro / nano structure region includes an insertion region, a transition region, and an exit region having a one-dimensional micro / nano structure or a two-dimensional micro / nano structure.

[0052] Those skilled in the art will understand that the core function of the micro / nano structure region of the optical waveguide is to control the optical path to transmit virtual images through diffraction effects. Among the three configuration methods mentioned above, integrating a two-dimensional micro / nano structure region means completing light coupling (introducing into the waveguide) and two-dimensional pupil expansion (expanding the field of view horizontally and vertically) in a single region, resulting in a more compact structure. A coupling region plus a coupling-out region indicates a clear division of labor between the two regions: the coupling micro / nano structure is responsible for introducing light, and the coupling micro / nano structure is responsible for directing the light out of the waveguide and into the human eye. A coupling region, a turning region, and a coupling-out region indicate the addition of a turning micro / nano structure for optical path redirection and initial pupil expansion, working in conjunction with the coupling micro / nano structure to achieve a superior two-dimensional pupil expansion effect. Different numbers of regions and micro / nano structure dimensions can collectively determine the complexity of optical path control and image display effects. Figure 6 This is a top view of a diffractive optical waveguide provided in an embodiment of the present invention. Figure 6 Taking the diffractive waveguide shown as an example, in the waveguide substrate 11 of this embodiment, the micro-nano structure region 100 may include a coupling-in region 110 and a coupling-out region 120.

[0053] Figure 7 This is a schematic diagram of another diffractive waveguide structure provided in this embodiment of the present invention, for reference. Figure 7 In an optional embodiment, the annular protective frame 23 is integrally connected to the low-fold adhesive layer 12.

[0054] This embodiment essentially integrates the annular protective frame 23 and the low-reflection adhesive layer 12 into a single structure through bonding. Specifically, an adhesive layer is formed on the surface of the low-reflection adhesive layer 12 by dispensing or printing, and the adhesive layer is positioned along the edge of the protective sheet. Then, the adhesive layer is bonded to the low-reflection adhesive layer 12 through a bonding process to form an integrated structure. This eliminates gaps between the annular protective frame 23 and the low-reflection adhesive layer 12, effectively preventing moisture from entering the low-reflection adhesive layer 12 through gaps.

[0055] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, combinations, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments. Many other equivalent embodiments may be included without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A diffractive optical waveguide, characterized in that, include: An optical waveguide substrate, wherein at least one side surface of the optical waveguide substrate is provided with at least one micro / nano structure region; A low-refractive-index adhesive layer, which covers one side surface of the optical waveguide substrate where the micro / nano structure region is provided; A protective layer covers the side surface of the low-refractive adhesive layer facing away from the optical waveguide substrate; the protective layer includes a central protective sheet and an annular protective frame; the orthographic projection of the annular protective frame onto the plane where the optical waveguide substrate is located surrounds the orthographic projection of the central protective sheet onto the plane where the optical waveguide substrate is located, and is adjacent to the edge of the orthographic projection of the central protective sheet onto the plane where the optical waveguide substrate is located; the micro / nano structure region is located in the orthographic projection of the central protective sheet onto the plane where the optical waveguide substrate is located.

2. The diffractive waveguide according to claim 1, characterized in that, The width of the annular protective frame is D1, and the distance between the side surface of the low-fold adhesive layer away from the optical waveguide substrate and the side surface of the central protective sheet away from the low-fold adhesive layer is L, where D1=L / K, 1.5≤K≤1.

8.

3. The diffractive waveguide according to claim 1, characterized in that, The surface of the annular protective frame facing away from the low-fold adhesive layer is flush with the surface of the central protective sheet facing away from the low-fold adhesive layer, and the edge of the annular protective frame away from the central protective sheet is flush with the edge of the low-fold adhesive layer.

4. The diffractive waveguide according to claim 1, characterized in that, The protective layer further includes an optical adhesive layer; the optical adhesive layer is located between the central protective sheet and the low-refractive adhesive layer; the orthographic projection of the optical adhesive layer onto the plane of the optical waveguide substrate coincides with the orthographic projection of the central protective sheet onto the plane of the optical waveguide substrate.

5. The diffractive waveguide according to claim 1, characterized in that, The annular protective frame is integrally connected to the low-fold adhesive layer.

6. The diffractive waveguide according to claim 1, characterized in that, The micro-nano structure region is provided with a micro-nano structure, and the thickness D2 of the low-fold adhesive layer is 1 to 3.5 times the height H of the micro-nano structure.

7. The diffractive waveguide according to claim 1, characterized in that, The optical waveguide substrate includes a glass substrate and a high-refractive-index adhesive layer located on one side surface of the glass substrate. The high-refractive-index adhesive layer has a micro / nano structure formed on the side surface of the high-refractive-index adhesive layer opposite to the glass substrate. The low-refractive-index adhesive layer covers the side surface of the high-refractive-index adhesive layer opposite to the glass substrate.

8. The diffractive waveguide according to claim 1, characterized in that, The at least one micro / nanostructure region includes an integrated micro / nanostructure region, wherein the integrated micro / nanostructure region has a two-dimensional micro / nanostructure. Alternatively, the at least one micro / nano structure region includes a coupling-in region and a coupling-out region, wherein the coupling-in region and the coupling-out region have a one-dimensional micro / nano structure or a two-dimensional micro / nano structure. Alternatively, the at least one micro / nano structure region includes an introducing region, a transition region, and an outtroducing region, wherein the introducing region, the transition region, and the outtroducing region have a one-dimensional micro / nano structure or a two-dimensional micro / nano structure.

9. The diffractive waveguide according to claim 1, characterized in that, The ring-shaped protective frame is waterproof and UV resistant.

10. The diffractive waveguide according to claim 1, characterized in that, It also includes an ink layer coated on the sidewalls of the optical waveguide substrate, the low-refractive adhesive layer, and the annular protective frame.

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