Optical waveguide device, display device, and method of manufacturing optical waveguide device

Abstract

The application discloses an optical waveguide device, which comprises a waveguide substrate, a grating body and an optical coating. The grating body is arranged in a grating region of a main surface of the waveguide substrate, and the optical coating covers at least part of a non-grating region of the main surface and the grating body. The optical coating comprises a first coating and a second coating arranged on the first coating, and the effective refractive index of the first coating and the second coating is lower than that of the grating body. In the non-grating region, the second coating and the first coating overlap with each other. On the grating body, the first coating only covers the top of the grating body, and the second coating covers at least the top and the bottom of the grating body. The optical waveguide device allows flexible and convenient design and manufacture, can greatly improve the grating diffraction efficiency and enhance the diffraction efficiency control ability between different duty cycles while ensuring the transmission and reflection rate. The application also discloses a display device with the optical waveguide device and a method for manufacturing the optical waveguide device.

Description

Technical Field

[0001] This invention relates to display technology based on diffractive optical waveguides; specifically, it relates to optical waveguide devices, display devices having optical waveguide devices, and methods for manufacturing optical waveguide devices. Background Technology

[0002] AR (Augmented Reality) glasses are gradually entering the consumer market. The mainstream solution for implementing AR glasses is a diffractive waveguide, which employs a waveguide device incorporating a grating coupler. Specifically, the diffractive waveguide uses a coupling grating as the input element to couple incident light carrying image information into the waveguide substrate, allowing it to propagate through total internal reflection within the waveguide. The diffractive waveguide also includes an output grating, and in some cases, a deflection grating. The deflection grating is used to dilate the pupil in at least one dimension and deflect the light to propagate towards the output grating. The output grating, on the other hand, dilates the pupil and couples the light out of the waveguide substrate, forming an output light field. The eye receives the light from the output light field, thus allowing it to observe the image carried by the incident light.

[0003] With the increasing prevalence of AR glasses applications, people are placing higher demands on aspects such as transmittance / reflectance and grating visibility, hoping that AR glasses will resemble ordinary glasses in form. To this end, for diffractive waveguides used in AR displays, researchers have attempted to improve transmittance and reduce reflectance by coating the non-grating regions and the transition / coupling grating regions of the diffractive waveguide. However, existing coating structures suffer from poor design flexibility, making it difficult to simultaneously meet the requirements for transmittance / reflectance of the waveguide / diffractive waveguide and grating diffraction efficiency. Furthermore, they suffer from technical bottlenecks such as low overall diffraction efficiency and insufficient ability to control diffraction efficiency between different sub-regions of the grating. In addition, some existing coating structures involve complex and costly manufacturing processes. Summary of the Invention

[0004] The purpose of this invention is to provide an optical waveguide device, a display device having an optical waveguide device, and a method for manufacturing an optical waveguide device, so as to at least partially overcome the problems in the prior art.

[0005] According to one aspect of the present invention, an optical waveguide device is provided, comprising: A waveguide substrate, wherein a main surface of the waveguide substrate includes a grating region and a non-grating region; A grating body, disposed in the grating region, and having a top, a bottom, and a sidewall connecting the top and the bottom; and An optical coating, covering at least a portion of the non-grating area and the grating body, is used to reduce reflection of external light. The optical coating includes a first coating and a second coating covering the first coating, wherein the effective refractive index n of the first coating is... e1 The effective refractive index n of the second coating e2 All are lower than the refractive index of the grating body; In at least a portion of the non-grating region, the second coating overlaps with the first coating; and On the grating body, the first coating covers only the top, and the second coating covers at least the top and bottom.

[0006] Advantageously, the effective refractive index n of the first coating e1 Within the range of 1.3-2, the effective refractive index n of the second coating is... e2 Within the range of 1.3-2.

[0007] Advantageously, the thickness H1 of the first coating on the top of the grating body and the thickness H2 of the second coating on the top of the grating body satisfy: 50nm≤H1+H2≤120nm, and 20nm≤H2≤100nm.

[0008] Advantageously, 15nm≤H1≤70nm.

[0009] Advantageously, the refractive index of each material of the first coating is in the range of 1.3-1.7, and the refractive index of each material of the second coating is in the range of 1.3-2; and the thickness H1 of the first coating on the top of the grating body and the thickness H2 of the second coating on the top of the grating body satisfy: 60nm≤H1+H2≤120nm, 15nm≤H1≤60nm, and 20nm≤H2≤100nm.

[0010] Advantageously, the first coating and the second coating each consist of only one film layer.

[0011] Advantageously, the first coating comprises a first material, the second coating comprises a second material, and the first material and the second material have different refractive indices.

[0012] Advantageously, the thickness H2 of the second coating on the top of the grating body and the thickness D2 of the second coating on the bottom of the grating body satisfy: D2≤H2.

[0013] Advantageously, D2 ≥ H2 / 3 or D2 ≥ 15 nm.

[0014] Advantageously, the second coating also covers the sidewalls of the grating body, and has an average thickness of W2 on the sidewalls, where W2 ≤ D2.

[0015] Advantageously, W2 ≥ H2 / 3 or W2 ≥ 15 nm.

[0016] Advantageously, the sidewalls include a first sidewall and a second sidewall opposite to each other, the first sidewall forming a first angle θ1 with the bottom greater than 90 degrees. o The second included angle θ2 formed by the second sidewall and the bottom is smaller than the first included angle θ1; wherein preferably, the thickness W of the second coating on the first sidewall is... 21 and the thickness W on the second sidewall 22 Satisfy: W 22 ≤W 21 And H2 / 3≤W 21 ≤D2≤H2.

[0017] Advantageously, the refractive index difference between any two adjacent film layers with a thickness of not less than 15 nm in the optical coating is less than 0.5, preferably less than 0.3.

[0018] Advantageously, the top of the grating body has a stepped shape, and the first coating covers at least the surface of the highest step of the stepped shape.

[0019] Advantageously, the grating body is configured to diffract a portion of the light propagating in the waveguide substrate along a first direction by total internal reflection with a predetermined order so that it leaves the grating body in a second direction different from the first direction, while allowing another portion of the light to continue propagating along the first direction by total internal reflection; and the grating body includes at least two regions with different grating duty cycles.

[0020] Advantageously, the grating body is a turn-off grating or a coupling grating, and the grating duty cycle varies between 0.3 and 0.7 in different regions of the grating body.

[0021] According to another aspect of the present invention, a display device is provided, which includes the optical waveguide device as described above.

[0022] Advantageously, the display device is a near-eye display device and further includes a lens and a frame for holding the lens close to the eye, the lens including the optical waveguide device.

[0023] According to another aspect of the present invention, a method for manufacturing an optical waveguide device is provided, the method comprising the following steps: (1) Provide waveguide substrate; (2) Apply a grating material to a main surface of the waveguide substrate, the main surface including a first region and a second region other than the first region; (3) Deposit a first coating to cover the first region and at least a portion of the second region, and make the effective refractive index n of the first coating... e1 The refractive index is lower than that of the grating material; (4) Etching is performed in the first region to remove portions of the first coating and the grating material; and (5) Deposit a second coating to cover the first region and at least a portion of the second region, and such that the effective refractive index n of the second coating is such that... e2 The refractive index is lower than that of the grating material.

[0024] Advantageously, the method further includes: between steps (2) and (3), performing pre-etching in the first region to remove a portion of the grating material to form a top surface of a predetermined shape.

[0025] Advantageously, the method further includes: between steps (4) and (5), performing supplementary etching in the first region to remove a portion of the grating material or to remove a portion of the first coating and the grating material.

[0026] Advantageously, the refractive index of each material of the first coating is in the range of 1.3-1.7, and the refractive index of each material of the second coating is in the range of 1.3-2; and the thickness H1 of the first coating and the thickness H2 of the portion of the second coating covering the first coating satisfy: 60nm≤H1+H2≤120nm, 15nm≤H1≤60nm, and 20nm≤H2≤100nm.

[0027] Advantageously, the first coating and the second coating each consist of only one film layer.

[0028] Advantageously, step (5) includes depositing a second coating using an isotropic or anisotropic process, such that the thickness H2 of the second coating on the first coating, the thickness D2 on the bottom of the grating material formed by etching, and the average thickness W2 on the sidewall of the grating material formed by etching satisfy: H2 / 3≤W2≤D2≤H2.

[0029] Advantageously, the sidewalls formed by etching the grating material include a first sidewall and a second sidewall that are opposite to each other, and the first sidewall forms a first angle θ1 with the bottom that is greater than 90 degrees. o The second included angle θ2 formed by the second sidewall and the bottom is smaller than the first included angle θ1; wherein preferably, step (5) includes depositing a second coating using an isotropic or anisotropic process, such that the thickness H2 of the second coating on the first coating, the thickness D2 on the bottom formed by etching the grating material, and the thickness W of the first sidewall are all greater than the thickness H2 of the second coating on the first coating.21 and the thickness W on the second sidewall 22 Satisfy: W 22 ≤W 21 And H2 / 3≤W 21 ≤D2≤H2.

[0030] In the optical waveguide device according to embodiments of the present invention, by applying differentiated multilayer coating structures on the grating, flexible and convenient multilayer, controllable refractive index matching design is possible, which significantly improves the overall diffraction efficiency of the grating while ensuring transmittance and reflectance, and enhances the ability to tune the diffraction efficiency between grating sub-regions with different duty cycles. Furthermore, the optical waveguide device according to embodiments of the present invention also simplifies the manufacturing process and reduces costs.

[0031] The display device according to embodiments of the present invention also has the above-mentioned technical advantages.

[0032] The method for manufacturing optical waveguide devices according to embodiments of the present invention has the technical advantages of simple process and low cost. Attached Figure Description

[0033] Other features, objects, and advantages of the invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings.

[0034] Figure 1 This is a schematic cross-sectional view of an example of an optical waveguide device according to an embodiment of the present invention.

[0035] Figure 2 This is a schematic cross-sectional view of another example of an optical waveguide device according to an embodiment of the present invention.

[0036] Figure 3 A plan view of an example of a diffractive optical waveguide employing an optical waveguide device according to an embodiment of the present invention.

[0037] Figure 4 The following are partially enlarged cross-sectional views of two examples of optical waveguide devices according to embodiments of the present invention, wherein the first coating and the second coating include more than one film layer.

[0038] Figure 5 The following are partially enlarged cross-sectional views of two examples of optical waveguide devices according to embodiments of the present invention, wherein the grating body is a grating of different types.

[0039] Figure 6 The diagram illustrates the thickness of the optical coating on multiple portions of the grating body in an optical waveguide device according to an embodiment of the present invention.

[0040] Figure 7This is a partially enlarged cross-sectional view of an example of an optical waveguide device according to an embodiment of the present invention, wherein the second coating has a different thickness on the sidewall of the grating body.

[0041] Figure 8 The graph shows the grating diffraction efficiency as a function of the incident angle of light in the waveguide substrate in Data Example 1.

[0042] Figure 9 The graph shown in Data Example 2 illustrates the variation of grating diffraction efficiency with the incident angle of light in the waveguide substrate.

[0043] Figure 10 The graph shown in Data Example 3 illustrates the variation of grating diffraction efficiency with the incident angle of light in the waveguide substrate.

[0044] Figure 11 The graph shown in Data Example 4 illustrates the variation of grating diffraction efficiency with the incident angle of light in the waveguide substrate.

[0045] Figure 12 for Figure 11 The curve shown is a magnified view of a portion of the curve, where the incident angle of light in the waveguide substrate is in the small angle range.

[0046] Figure 13 The cross-sectional diagram schematically illustrates the characteristics of light rays with large and small incident angles propagating and coupling out in the waveguide substrate of a diffractive waveguide.

[0047] Figure 14 The planar diagram schematically illustrates the characteristics of light rays with large and small incident angles propagating and coupling out in the waveguide substrate.

[0048] Figure 15 The block diagram illustrates the basic flow of a method for manufacturing an optical waveguide device according to an embodiment of the present invention.

[0049] Figure 16 For application Figure 15 The diagram shows schematic cross-sectional views of examples of structures obtained at different steps in the basic process.

[0050] Figure 17 This is a flowchart illustrating an example of a method for manufacturing an optical waveguide device according to an embodiment of the present invention.

[0051] Figure 18 For application Figure 17 The method for manufacturing optical waveguide devices is shown in the schematic cross-sectional view of an example of the structure obtained at different steps.

[0052] Figure 19 This is a flowchart illustrating another example of a method for manufacturing an optical waveguide device according to an embodiment of the present invention.

[0053] Figure 20 For application Figure 19 The method for manufacturing optical waveguide devices is shown in the schematic cross-sectional view of an example of the structure obtained at different steps. Detailed Implementation

[0054] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. For ease of description, only the parts relevant to the invention are shown in the drawings. It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0055] First, refer to Figures 1 to 7 An optical waveguide device according to an embodiment of the present invention is described.

[0056] like Figure 1 As shown, the optical waveguide device 1 according to an embodiment of the present invention includes a waveguide substrate B, a grating body 10, and an optical coating 20. A main surface S of the waveguide substrate B includes a grating region G and a non-grating region NG. The grating body 10 is disposed in the grating region G and has a top a, a bottom b, and a sidewall c connecting the top a and the bottom b. The optical coating 20 covers at least a portion of the non-grating region NG and the grating body 10 to reduce reflection of ambient light. Here, "grating region" refers to the region on the main surface S where a grating is formed, and "non-grating region" refers to the region on the main surface S where no grating is formed.

[0057] According to an embodiment of the present invention, the optical coating 20 includes a first coating 21 and a second coating 22 covering the first coating 21, wherein the effective refractive index n of the first coating 21 is... e1 The effective refractive index n of the second coating 22 e2 Both are lower than the refractive index n0 of the grating body 10.

[0058] According to an embodiment of the present invention, in at least a portion of the non-grating region NG, the second coating 22 overlaps with the first coating 21; and on the grating body 10, the first coating 21 covers only the top a, while the second coating 22 covers at least the top a and the bottom b. As an example, such as Figure 1 As shown, the second coating 22 can cover the top a, bottom b and sidewall c of the grating body 10.

[0059] As can be seen, in the optical waveguide device 1 according to the embodiment of the present invention, in the non-grating region NG and the top a of the grating body 10, the refractive index and thickness of the optical coating 20 are jointly determined by the first coating 21 and the second coating 22; while in the bottom b and sidewall c of the grating body 10, the optical coating 20 is actually independently formed by the second coating 22.

[0060] This differentiated multilayer coating structure allows for relatively independent design and adjustment of the optical coating portions located in the non-grating region and on top of the grating body, as well as the optical coating portions located at the bottom and sidewalls of the grating body. This enables flexible and convenient control over aspects such as transmittance and reflectance as well as grating diffraction efficiency.

[0061] Specifically, this invention is based on the discovery that the optical coating at the top of the grating is the primary factor affecting the transmittance / reflectance of the grating region to ambient light. By making the optical coating portions located in the non-grating region and at the top of the grating body have the same structure, the transmittance and reflectance of both the non-grating and grating regions to external light can be effectively optimized simultaneously to achieve the goal of enhancing transmittance and resisting reflection. Furthermore, by confining the first coating to the top, the top coating can be optimized independently without sacrificing the adjustment function of the optical coating at the bottom and sidewalls of the grating, thereby optimizing the transmittance and reflectance.

[0062] Meanwhile, at the bottom and sidewalls of the grating body, the optical coating is actually independently formed by the second coating 22. Thus, the thickness of the second coating on the bottom and sidewalls of the grating body can be designed independently of the first coating, allowing the second coating 22 to adjust the air gap ac formed within the grating structure relatively independently (see...). Figure 2 The depth and width of the second coating 22 at the bottom b can be adjusted to control the grating diffraction efficiency. Specifically, the depth of the air gap ac can be adjusted by changing the difference between the thickness of the second coating 22 at the bottom b and the sum of the thicknesses of the first coating 21 and the second coating 22 at the top a; the width of the air gap ac can be adjusted by changing the thickness of the second coating 22 on the sidewall c. In this way, the grating diffraction efficiency can be easily controlled by designing the second coating 22 in the optical waveguide device 1.

[0063] The optical waveguide device 1 according to embodiments of the present invention not only facilitates flexible and convenient design to balance the requirements of transmittance and reflectance as well as grating diffraction efficiency, but also achieves excellent optical efficiency. The data examples below show that the optical waveguide device according to embodiments of the present invention can significantly improve the overall diffraction efficiency (average diffraction efficiency) of the grating while sufficiently suppressing reflectance. Furthermore, the optical waveguide device 1 also helps to increase the difference in diffraction efficiency between grating sub-regions with larger and smaller duty cycles, i.e., enhances the ability to tune the diffraction efficiency between different sub-regions of the grating. This is particularly advantageous for transition gratings and coupling gratings in diffractive optical waveguides.

[0064] Furthermore, and very importantly, the optical waveguide device 1 according to embodiments of the present invention also facilitates simplified manufacturing processes and reduced costs. This is primarily because the structure of the optical waveguide device 1 allows the first coating 21 to be processed / etched simultaneously during the etching step of processing the grating body 10, such that the first coating 21 only covers the top a and non-grating region NG of the grating body 10, while exposing the bottom b and sidewalls c of the grating body 10. Therefore, no additional steps or additional masks are required for the "patterning" of the first coating 21. Simultaneously, the second coating 22 has a simple structure and can be easily formed using conventional coating processes.

[0065] like Figure 1 As shown, the optical coating 20 can cover only a portion of the non-grating region NG. Alternatively, as... Figure 2 As shown, the optical coating 20 can also cover the entire non-grating area NG of the main surface S1.

[0066] According to embodiments of the present invention, the optical waveguide device 1 may include one or more grating bodies 10 covered by the optical coating 20; the optical waveguide device 1 may also include other gratings 30 not covered by the optical coating 20, such as... Figure 1 and Figure 2 As shown.

[0067] Figure 3 A plan view of an example of a diffractive optical waveguide employing an optical waveguide device 1 according to an embodiment of the present invention is shown. Figure 3 In the example shown, one main surface (main surface S1, see...) of the waveguide substrate B of the optical waveguide device 1 Figure 1 The first grating body 10-1 and the second grating body 10-2 are provided on the surface, and the other main surface (main surface S2, see) is opposite. Figure 2 Other gratings 30 are provided on the optical waveguide 2; the grating 30 is used as the coupling grating g1 of the diffractive waveguide 2, and the first grating body 10-1 and the second grating body 10-2 are used as the turning grating g2 and the coupling grating g3 of the diffractive waveguide 2, respectively; the optical coating 20 of the optical waveguide device 1 covers the turning grating g2 and the coupling grating g3.

[0068] Depending on the needs of different applications, the optical coating 20 may cover only the transition grating g2 or the coupling grating g3, except for the non-grating areas. In some cases, the coupling grating g3 or the transition grating g2 is disposed on another main surface S2.

[0069] It should be understood that the optical waveguide device according to the embodiments of the present invention can also be applied to a diffractive optical waveguide that does not employ a folding grating, wherein the optical waveguide device 1 may include a grating body 10 serving as a coupling grating, and an optical coating 20 covering the coupling grating.

[0070] In a diffractive waveguide, both the bend grating and the coupling grating are configured to diffract a portion of the light propagating along a first direction via total internal reflection in the waveguide substrate at a predetermined order, causing it to exit along a second direction different from the first direction, while allowing the remaining light to continue propagating along the first direction via total internal reflection. In other words, both the bend grating and the coupling grating have a pupil-expanding effect. Pupil expansion alters the distribution of light energy. To improve the uniformity of light energy after pupil expansion, the bend grating and / or the coupling grating preferably include at least two sub-regions with different grating duty cycles to adjust the grating diffraction efficiency, thereby adjusting the ratio of light propagating via total internal reflection to light diffracted in that sub-region, thus improving uniformity.

[0071] The optical waveguide device according to embodiments of the present invention can enhance the ability of duty cycle to control grating diffraction efficiency, and is therefore highly advantageous for applications in which the grating body is configured to have the aforementioned pupil-expanding effect and includes at least two regions with different duty cycles. Preferably, the grating body is a transition grating and / or a coupling grating, and the grating duty cycle in different sub-regions of the grating body varies between 0.3 and 0.7.

[0072] Return to reference Figure 1 ,exist Figure 1 In the example shown, the first coating 21 and the second coating 22 each comprise a single film layer, which is advantageous for simplifying the structure and process. In this case, the first coating 21 is formed of a first material with a refractive index of n1, where n1 is the effective refractive index n of the first coating 21. e1 The second coating 22 is formed of a second material with a refractive index of n2, where n2 is the effective refractive index n of the second coating 22. e2 Both n1 and n2 should be lower than the refractive index n0 of the grating body 10 to reduce the reflectivity of the optical waveguide device 1 to external light. Advantageously, the refractive indices n1 and n2 are also lower than the refractive index of the waveguide substrate.

[0073] However, the present invention is not limited to the case where the first coating 21 and the second coating 22 each comprise a single film layer. For example, Figure 4 Two examples are shown, where figure (a) shows a first coating 21 comprising film layers 21a and 21b, and figure (b) shows a second coating 22 comprising film layers 22a and 22b. In other examples not shown, the first and second coatings may each have more film layers, and / or the first and second coatings may simultaneously comprise more than two film layers.

[0074] When the first coating and / or the second coating comprises more than one layer, the effective refractive index n e1 n e2 The value n can be obtained by taking the volume-weighted average of the refractive indices of each film layer. e= ∑(film volume * film refractive index) / total volume. According to an embodiment of the present invention, the effective refractive index n e1 n e2 The refractive index n0 should be lower than that of the grating body 10 to reduce the reflectivity of the optical waveguide device 1 to external light. Advantageously, the refractive index n0 should be lower than that of the grating body 10. e1 and n e2 It is also less than the refractive index of the waveguide substrate.

[0075] When the first and / or second coatings include more than one layer, more layers of refractive index and thickness can be introduced as parameters / variables to adjust the performance of the optical waveguide device, increasing flexibility. This is advantageous in some cases.

[0076] Advantageously, the effective refractive index n of the first coating e1 The effective refractive index n of the second coating e2 They are respectively in the range of 1.3-2.

[0077] More advantageously, the refractive index of each material in the first coating is in the range of 1.3-1.7, and the refractive index of each material in the second coating is in the range of 1.3-2.

[0078] In some embodiments, the first coating comprises a first material, the second coating comprises a second material, and the first and second materials have different refractive indices. Thus, the refractive indices of the first and second materials can be used as different parameters / variables to adjust the performance of the optical waveguide device, improving design flexibility and enhancing optical efficiency.

[0079] However, the present invention is not limited to the case where the first coating and the second coating contain materials with different refractive indices. In some embodiments, the first coating and the second coating are each a single film layer and are formed of the same material or materials having the same or similar refractive indices. Since the coverage areas of the first coating and the second coating are different in the optical waveguide device 1 according to the embodiments of the present invention, and their thicknesses can be adjusted separately, even if the first coating and the second coating have the same or similar refractive indices, it is still possible to flexibly and conveniently design and manufacture the optical coating 20 and the optical waveguide device 1 and obtain good transmittance and reflectance and grating diffraction efficiency.

[0080] According to a preferred embodiment of the present invention, the refractive index difference between any two adjacent film layers with a thickness of not less than 15 nm in the optical coating is less than 0.5, more preferably less than 0.3. This helps to control and improve the curve distribution of the grating diffraction efficiency curve in the small incident angle range, avoids fluctuations in diffraction efficiency, and is beneficial to improving the field uniformity of the light field.

[0081] According to embodiments of the present invention, the grating body 10 in the optical waveguide device 1 can be a rectangular grating, or it can be, for example, a tilted grating, a trapezoidal grating, or a stepped grating, such as... Figure 5 As shown. When the grating body 10 is a stepped grating, as... Figure 5 As shown in figures (c) and (d), the first coating 21 at least covers the highest step surface of the stepped shape at the top of the grating. Furthermore, the grating body 10 can also be a grating type with a top surface having other predetermined shapes.

[0082] Figure 6 The diagram illustrates the thickness of the optical coating on multiple portions of the grating body in an optical waveguide device according to an embodiment of the present invention. For example... Figure 6 As shown, the thickness of the first coating 21 on the top a of the grating body 10 is H1; the thickness of the second coating 22 on the top a of the grating body 10 is H2, the thickness on the bottom b is D2, and the thickness on the sidewall c is W2. If the thickness of the above-mentioned portions of the coating is not uniform, then the thicknesses H1, H2, D2, and W2 refer to the average thickness of the corresponding portions. Furthermore, when the first coating 21 and the second coating 22 include more than one film layer, the thicknesses H1, H2, D2, and W2 refer to the total thickness of all film layers of the first coating 21 or the second coating 22.

[0083] Advantageously, the thickness H1 of the first coating 21 and the thickness H2 of the second coating 22 satisfy: 50nm ≤ H1 + H2 ≤ 120nm, and 20nm ≤ H2 ≤ 100nm. More advantageously, the thickness H1 further satisfies: 15nm ≤ H1 ≤ 70nm.

[0084] Preferably, the refractive index of each material of the first coating 21 is in the range of 1.3-1.7, the refractive index of each material of the second coating 22 is in the range of 1.3-2, and the thickness H1 of the first coating 21 and the thickness H2 of the second coating 22 satisfy: 60nm≤H1+H2≤120nm, 15nm≤H1≤60nm, and 20nm≤H2≤100nm.

[0085] The preferred range of the aforementioned thickness is beneficial for optimizing the transmittance and reflectance of the optical waveguide device 1 to external light (i.e., anti-reflection and anti-transmission), and leaves sufficient adjustment space for improving the overall grating diffraction efficiency and enhancing the diffraction efficiency control capability.

[0086] Preferably, the thickness D2 of the second coating on the bottom of the grating body is less than or equal to the thickness H2 of the second coating on the top of the grating body, i.e., D2 ≤ H2. Furthermore, it is preferable that the thickness W2 of the second coating on the sidewall of the grating body is less than or equal to the thickness D2 of the second coating, i.e., W2 ≤ D2. This allows for the retention of a deeper and wider air gap in a sub-region of the grating body with a smaller duty cycle while ensuring sufficient adjustment capability for transmittance and reflectance, thereby further improving the overall grating diffraction efficiency and enhancing the diffraction efficiency control capability.

[0087] Preferably, D2 ≥ 15 nm and W2 ≥ 15 nm. This ensures that the bottom b and sidewall c of the grating body 10 have optical coatings of a certain thickness, which helps to further reduce the reflectivity of the grating body 10 to external light and correspondingly increase the transmittance. When the thickness H2 is large, it is preferable that D2 ≥ H2 / 3 and / or W2 ≥ H2 / 3.

[0088] although Figure 1 , Figure 2 , Figures 4-6 The second coating is shown in the embodiments as having the same thickness on all sidewalls of the grating body, but the invention is not limited thereto. In some examples, the second coating may have different thicknesses on two opposite sidewalls of the grating body.

[0089] Figure 7 A preferred example is shown in which the second coating has different thicknesses on the sidewalls. Figure 7 In the example shown, the grating body 10 has an asymmetrical structure, wherein the sidewalls c include a first sidewall c1 and a second sidewall c2 that are opposite to each other, and the first sidewall c1 forms a first angle θ1 with the bottom b of the grating body 10, where θ1 is greater than 90°. o The second sidewall c2 forms a second included angle θ2 with the bottom b, where θ2 is less than θ1; the second coating 22 has a thickness W on the first sidewall c1. 21 The second sidewall c2 has a thickness W 22 W 22 <W 21 More preferably, it further satisfies: H² / 3 ≤ W 22 .

[0090] Smaller thickness W 22 This allows for the retention of a wider air gap in sub-regions with smaller duty cycles within the grating body, thereby improving grating diffraction efficiency. This results in better overall performance.

[0091] References above Figure 6 Similarly, in the discussion, it is preferred that H² / 3 ≤ W. 21 ≤D2≤H2. , in order to balance the transmittance and reflectance of the optical waveguide device and the diffraction efficiency of the grating.

[0092] Furthermore, it should be understood that, depending on the needs of different applications, when the grating body is a grating with vertical sidewalls, such as a rectangular grating or a stepped grating, the second coating may have different thicknesses on the sidewalls of the grating body. For example, when external light is incident at a specific angle, the second coating may have different thicknesses on two opposite sidewalls of this type of grating.

[0093] The following will refer to Figures 8 to 14The technical advantages of the optical waveguide device according to embodiments of the present invention are illustrated through data examples. In the data examples of this application: the ambient medium is air (refractive index 1), the refractive index of the waveguide substrate is 2, the grating body is a rectangular grating, and the wavelength used in the simulation calculation of the grating diffraction efficiency is 530 nm.

[0094] (Data Example 1) Example 1 compares and analyzes diffractive waveguides using traditional coatings and diffractive waveguides using the optical coatings of this invention. The coated grating body is a transition grating: the refractive index of the grating body is n0=2.4, the grating period is 290nm, the grating depth is 50nm, and the duty cycle of each sub-region is set in the range of 0.3-0.7.

[0095] The conventional coating used in Example 1 consists of a single film layer with a thickness of 80 nm and a refractive index n. c =1.4, covering the entire surface of the grating body. Traditional coatings suppress reflectivity to below 2%, and are optimized for the diffraction efficiency of the fold grating.

[0096] The optical coating of the present invention used in Example 1 includes a first coating and a second coating, each being a single film layer: the first coating has a refractive index n1 = 1.4 and a thickness H1 = 30 nm; the second coating has a refractive index n2 = 1.6 and a thickness H2 = D2 = W. 21 =W 22 =50nm. The total thickness H1+H2 of this optical coating is the same as that of a conventional coating, ensuring similar high transmittance and low reflectance (reflectance below 2%).

[0097] In Example 1, simulations were performed to calculate the diffraction efficiency of the folding grating at duty cycles of 0.3 and 0.7 under the conditions of the conventional coating and the optical coating of the present invention. Figure 8 The graph shown in Data Example 1 illustrates the variation of grating diffraction efficiency with the incident angle (i.e., total reflection angle) of light within the waveguide substrate.

[0098] like Figure 8 As shown, compared with traditional coatings, the optical coating of the present invention yields a larger difference between the grating diffraction efficiency curves at duty cycles of 0.3 and 0.7. This means that the diffraction efficiency of the grating can be more effectively controlled by changing the duty cycle, i.e., the diffraction efficiency control capability between large and small duty cycles is stronger.

[0099] At the same time, from Figure 8As can be seen, compared with traditional coatings, the optical coating of this invention achieves a higher overall diffraction efficiency (average diffraction efficiency), and the upper limit of diffraction efficiency obtained at a duty cycle of 0.3 is significantly higher. In diffractive waveguides, the transition grating typically has a larger duty cycle near the beginning of the coupling grating, while the opposite end has a smaller duty cycle. Since light is attenuated most severely at the end of the transition grating, the higher the diffraction efficiency of the transition grating in the end region with a smaller duty cycle, the more beneficial it is to improving the brightness and uniformity of the diffractive waveguide display. Therefore, the optical coating of this invention is suitable for use in transition gratings of diffractive waveguides, which is beneficial to improving the brightness and uniformity of diffractive waveguide displays.

[0100] (Data Example 2) Example 2 compares and analyzes two different cases of diffractive waveguides using traditional coating and optical coatings of the present invention. The coated grating body is a transition grating: the refractive index of the grating body is n0=2.4, the grating period is 290nm, the grating depth is 40nm, and the duty cycle of each sub-region is set in the range of 0.3-0.8.

[0101] The conventional coating used in Example 2 consists of a single film layer with a thickness of 80 nm and a refractive index n. c =1.45, covering the entire surface of the grating body. Traditional coatings suppress reflectivity to below 2%, and are optimized for the diffraction efficiency of the fold grating.

[0102] In Case 1, the optical coating includes a first coating and a second coating, each a single layer: the first coating has a refractive index n1 = 1.45 and a thickness H1 = 25 nm; the second coating has a refractive index n2 = 1.62 and a thickness H2 = D2 = W. 21 =W 22 =55nm.

[0103] In Case 2, the optical coating includes a first coating and a second coating, each a single layer: the first coating has a refractive index n1 = 1.45 and a thickness H1 = 25 nm; the second coating has a refractive index n2 = 1.62 and a thickness H2 = D2 = 55 nm. 21 =W 22 =27nm.

[0104] In Case 1 and Case 2, the total thickness H1+H2 of the optical coating is the same as that of the traditional coating, ensuring similar high transmittance and low reflectance (reflectance below 2%).

[0105] In Example 2, simulations were performed to calculate the diffraction efficiency of the folding grating at duty cycles of 0.3 and 0.8 under the conditions of the conventional coating and the optical coating of the present invention. Figure 9The graph shown in Data Example 2 illustrates the variation of grating diffraction efficiency with the incident angle (i.e., total reflection angle) of light within the waveguide substrate.

[0106] like Figure 9 As shown, compared with traditional coatings, the optical coating of the present invention yields a larger difference between the grating diffraction efficiency curves at duty cycles of 0.3 and 0.8. This means that the diffraction efficiency of the grating can be more effectively controlled by changing the duty cycle, i.e., the diffraction efficiency control capability between large and small duty cycles is stronger.

[0107] At the same time, from Figure 9 It can be seen that, compared with traditional coatings, the optical coating of this invention achieves a higher overall diffraction efficiency (average diffraction efficiency), and the upper limit of diffraction efficiency obtained at a duty cycle of 0.3 is significantly higher, which is more conducive to improving the brightness and uniformity of diffractive waveguide displays.

[0108] Furthermore, in the optical coatings of the present invention, a comparison reveals that the optical coating of Example 2 exhibits a larger difference in grating diffraction efficiency at duty cycles of 0.3 and 0.8, resulting in higher overall diffraction efficiency, and also a higher upper limit for diffraction efficiency at a duty cycle of 0.3. This indicates that in the optical coatings of the present invention, a thickness W2 of the second coating on the sidewall of the grating body being less than the thickness D2 at the bottom of the grating body is beneficial for improving grating diffraction efficiency.

[0109] (Data Example 3) Example 3 compares and analyzes diffractive waveguides using traditional coatings and diffractive waveguides using the optical coatings of this invention. The coated grating body is a coupling grating: the refractive index of the grating body is n0=2.4, the grating period is 350nm, the grating depth is 30nm, and the duty cycle of each sub-region is set in the range of 0.3-0.7.

[0110] The conventional coating used in Example 3 consists of a single film layer with a thickness of 70 nm and a refractive index n. c =1.5, covering the entire surface of the grating body. Traditional coatings suppress reflectivity to below 2%, and are optimized for the diffraction efficiency of the fold grating.

[0111] The optical coating of the present invention used in Example 3 includes a first coating and a second coating, each being a single film layer: the first coating has a refractive index n1 = 1.65 and a thickness H1 = 35 nm; the second coating has a refractive index n2 = 1.5 and a thickness H2 = D2 = W. 21 =W 22 =45nm. The total thickness H1+H2 of this optical coating is similar to that of traditional coatings, ensuring similar high transmittance and low reflectance (reflectance below 2%).

[0112] In Example 3, simulations were performed to calculate the diffraction efficiency of the folding grating at duty cycles of 0.3 and 0.7 under the conditions of the conventional coating and the optical coating of the present invention. Figure 10 The graph shown in Data Example 3 illustrates the variation of grating diffraction efficiency with the incident angle (i.e., total reflection angle) of light within the waveguide substrate.

[0113] from Figure 10 As can be seen, compared to traditional coatings, the optical coating of this invention exhibits a larger difference between the grating diffraction efficiency curves at duty cycles of 0.3 and 0.7, resulting in higher overall diffraction efficiency. Furthermore, the upper limit of diffraction efficiency obtained at a duty cycle of 0.3 is significantly higher. In diffractive waveguides, similar to transition gratings, the coupling grating typically has a larger duty cycle at its light input end to provide a lower coupling diffraction efficiency, while the opposite end has a smaller duty cycle to provide a larger coupling diffraction efficiency, thereby adjusting the uniformity of the coupled light field. Therefore, the optical coating of this invention is suitable for application to coupling gratings in diffractive waveguides, which is beneficial for improving the brightness and uniformity of diffractive waveguide displays.

[0114] (Data Example 4) Example 4 analyzes the effect of the refractive index difference between adjacent effective optical layers in an optical waveguide device according to an embodiment of the present invention on the grating diffraction efficiency. Here, "effective optical layer" refers to a film layer with a thickness of not less than 15 nm in the optical coating.

[0115] Specifically, in Data Example 4, the duty cycle of the grating body is set to 0.6, and the optical coating includes a first coating and a second coating, each being a single film layer. The refractive index of the first coating is fixed (n1=1.4), and there is a refractive index difference delta_n=n2-n1 between the first coating and the second coating.

[0116] In Example 4, the grating diffraction efficiency was simulated and calculated when the refractive index difference delta_n changed from 0.2 to 0.6 while other conditions remained unchanged. Figure 11 The graph showing the diffraction efficiency of the grating as a function of the incident angle of light in the waveguide substrate in Data Example 4 is presented. For clarity, Figure 12 Further magnification shows Figure 11 The portion of the curve shown is within the small incident angle range.

[0117] like Figure 11 and Figure 12 As shown, when the refractive index difference delta_n reaches 0.6, the grating diffraction efficiency curve exhibits sudden fluctuations in the small incident angle range.

[0118] The abrupt fluctuations in the grating diffraction efficiency curve within the small incident angle range lead to a deterioration in the field-of-view uniformity of the diffracted waveguide, meaning that the brightness in the displayed image becomes uneven across different field-of-view angles. To facilitate understanding, Figure 13 and Figure 14 The propagation and diffraction characteristics of light rays with large and small incident angles within the waveguide substrate are schematically illustrated using cross-sectional and planar views, respectively. (Refer to reference...) Figure 13 and Figure 14 Image light from the optical engine L im Image light is coupled into the waveguide substrate via coupling grating g1, and after being coupled into the waveguide substrate B, it undergoes total internal reflection at different incident angles, such as... Figure 13 As shown, ray L1 (shown by the solid line), with a large angle of incidence, is reflected with a larger step size, while ray L2 (shown by the dashed line), with a small angle of incidence, is reflected with a smaller step size. (Refer to...) Figure 14 Ray L1 is diffracted in the effective turning region e1 of the turning grating g2 and redirected towards the effective coupling region e1' of the coupling grating g3, and then couples out towards the eyebox in the effective coupling region e1'. Ray L2 is diffracted in the effective turning region e2 of the turning grating g2 and redirected towards the effective coupling region e2' of the coupling grating g3, and then couples out towards the eyebox in the effective coupling region e2'. It can be seen that compared to ray L1 with a large incident angle, ray L2 with a small incident angle forms a high-density light energy distribution in both the turning grating g2 and the coupling grating g3 due to its smaller reflection step size (see...). Figure 13 As shown), and the propagation path in the folding grating g2 and the coupling grating g3 is longer (see...). Figure 14 (As shown). Therefore, even a tiny change in the diffraction efficiency of the gratings g2 and g3 in the small incident angle range will cause a significant change in the amount of light L2 at the small incident angle that is ultimately coupled out to the eyebox; and this sudden fluctuation in the diffraction efficiency curve in the small incident angle range will cause a drastic fluctuation in the amount of light corresponding to adjacent field angles in the light field coupled out to the eyebox, resulting in a significant deterioration in the uniformity of the field of view.

[0119] Figure 11 and Figure 12 It is also shown that when the refractive index difference delta_n is 0.5, the fluctuations in the grating diffraction efficiency curve in the small incident angle range are essentially suppressed, and as the refractive index difference delta_n further decreases, the overall grating diffraction efficiency curve increases. Therefore, it can be understood that a refractive index difference of less than 0.5 between the first and second coatings can help control and improve the curve distribution of the grating diffraction efficiency curve in the small incident angle range, avoiding fluctuations in diffraction efficiency and improving the field uniformity of the light field; a refractive index difference of less than 0.3 is even better.

[0120] The optical waveguide device according to embodiments of the present invention has been described above. According to embodiments of the present invention, a display device is also provided, which includes the optical waveguide device described above. This display device is preferably a near-eye display device, and further includes a lens and a frame for holding the lens close to the eye, the lens including the optical waveguide device.

[0121] Next, refer to Figures 15 to 20 A method for manufacturing an optical waveguide device according to an embodiment of the present invention is described.

[0122] Figure 15 The basic flow of a method for manufacturing an optical waveguide device according to an embodiment of the present invention is illustrated in the block diagram; Figure 16 The application is illustrated schematically. Figure 15 The diagram shows the structure obtained at different steps of the basic process. In short, as... Figure 15 As shown, a method 100 for manufacturing an optical waveguide device according to an embodiment of the present invention includes the following steps: S10: Provides waveguide substrate; S20: Apply grating material; S30: First coating applied; S40: Etching; and S50: Apply a second coating.

[0123] Specifically, in step S20, as Figure 16 As shown in figure (a), a grating material 10a is applied on a main surface S1 of a waveguide substrate B. The main surface S1 includes a first region and a second region other than the first region.

[0124] In step S30, as Figure 16 As shown in figure (b), a first coating 21 is deposited to cover the first region and at least a portion of the second region, such that the effective refractive index n of the first coating 21 is such that... e1 It is lower than the refractive index of the grating material.

[0125] In step S40, as Figure 16 As shown in the middle figure (c), etching is performed in the first region to remove a portion of the first coating 21 and the grating material 10a.

[0126] exist Figure 16 In the example shown in Figure (c), after step S40, the grating material 10a is etched to form the grating body 10. However, it should be understood that in other examples, the grating material 10a may need to undergo further processing, such as etching again, to form the grating body 10; the present invention is not limited in this respect.

[0127] In step S50, as Figure 16 As shown in figure (d), a second coating 22 is deposited to cover the first region and at least a portion of the second region, such that the effective refractive index n of the second coating 22 is such that... e2 It is lower than the refractive index of the grating material.

[0128] In the method for manufacturing an optical waveguide device according to an embodiment of the present invention, the first coating is processed / etched simultaneously during the etching step of processing the grating body 10, such that the first coating only covers the top of the grating body and the non-grating area, while exposing the bottom and sidewalls of the grating body. This eliminates the need for additional steps or additional masks for "patterning" the first coating. Meanwhile, the second coating 22 has a simple structure and can be easily formed using conventional coating processes.

[0129] Advantageously, the refractive index of each material in the first coating is in the range of 1.3-1.7, and the refractive index of each material in the second coating is in the range of 1.3-2.

[0130] Preferably, the thickness H1 of the first coating and the thickness H2 of the portion of the second coating covering the first coating satisfy: 60nm ≤ H1 + H2 ≤ 120nm, 15nm ≤ H1 ≤ 60nm, and 20nm ≤ H2 ≤ 100nm. These preferred thickness ranges are beneficial for optimizing the transmittance and reflectance of the optical waveguide device 1 to external light (i.e., anti-reflection and anti-transmission), and leave sufficient adjustment space for improving the overall grating diffraction efficiency and enhancing the diffraction efficiency control capability.

[0131] The first and second coatings can each consist of only one film layer, which is advantageous for simplifying the manufacturing process.

[0132] Preferably, step S50 includes depositing a second coating using an isotropic or anisotropic process, such that the thickness H2 of the second coating on the first coating, the thickness D2 on the bottom of the grating material formed by etching, and the thickness W2 on the sidewalls of the grating material formed by etching satisfy: H2 / 3 ≤ W2 ≤ D2 ≤ H2. This allows for the retention of a deeper and wider air gap in a sub-region with a smaller duty cycle within the grating body while ensuring sufficient adjustment capability for transmittance and reflectance, thereby further improving the overall grating diffraction efficiency and enhancing the diffraction efficiency control capability.

[0133] In some advantageous examples, the sidewalls formed by etching the grating material include a first sidewall and a second sidewall that are opposite to each other, and the first sidewall forms a first angle θ1 with the bottom that is greater than 90 degrees. oThe second included angle θ2 formed by the second sidewall and the bottom is smaller than the first included angle θ1; and preferably, step S50 includes depositing a second coating using an isotropic or anisotropic process, such that the thickness H2 of the second coating on the first coating, the thickness D2 on the bottom formed by etching the grating material, and the thickness W on the first sidewall are all equal. 21 and the thickness W on the second sidewall 22 Satisfy: W 22 ≤W 21 And H2 / 3≤W 21 ≤D2≤H2. More preferably, it further satisfies: H2 / 3≤W 22 .

[0134] exist Figure 15 Based on the illustrated process, the method for manufacturing optical waveguide devices according to embodiments of the present invention can be implemented in different ways. For example, Figure 17 and Figure 19 They are shown respectively Figure 15 Different examples of method 100 are shown, namely method 100A and method 100B; Figure 18 and Figure 20 Examples of structures obtained by applying method 100A and method 100B at different steps are shown below. Method 100A and method 100B will be described separately below.

[0135] like Figure 17 As shown, the method 100A for manufacturing an optical waveguide device includes the following steps: S10: Provides waveguide substrate; S20: Apply grating material; S25: Pre-etching; S30: First coating applied; S40: Etching; and S50: Apply a second coating.

[0136] Steps S10, S20, S30, S40, and S50 in method 100A can be referenced above. Figure 15 and Figure 16 Steps S10, S20, S30, S40, and S50 in Method 100 are performed in the same manner and will not be repeated here.

[0137] In step S25, as Figure 18 As shown in figure (b), pre-etching is performed in the first region to remove a portion of the grating material 10a to form a top surface of a predetermined shape. Figure 18 In the example shown, the top of the grating material is pre-etched to form a stepped surface. However, the method according to embodiments of the present invention is not limited to this. For example, the top surface may also include a bevel.

[0138] like Figure 18 As shown, the method 100B for manufacturing an optical waveguide device includes the following steps: S10: Provides waveguide substrate; S20: Apply grating material; S30: First coating applied; S35: Additional etching; S40: Etching; and S50: Apply a second coating.

[0139] Steps S10, S20, S30, S40, and S50 in method 100B can be referenced above. Figure 15 and Figure 16 Steps S10, S20, S30, S40, and S50 in Method 100 are performed in the same manner and will not be repeated here.

[0140] In step S35, as Figure 20 As shown in the middle figure (d), supplementary etching is performed in the first region to further remove portions of the grating material or to remove portions of the first coating and the grating material. Figure 20 In the example shown, the top of the grating material is etched and supplemented with additional etching to form a stepped shape at the top of the grating. However, the method according to embodiments of the present invention is not limited to this. For example, the top of the grating may also include a bevel.

[0141] Those skilled in the art should understand that the scope of the invention involved in this application is not limited to technical solutions formed by specific combinations of the above-mentioned technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-mentioned technical features or their equivalent features without departing from the inventive concept. For example, technical solutions formed by substituting the above-mentioned features with technical features disclosed in this application (but not limited to) that have similar functions.

Claims

1. An optical waveguide device, comprising: A waveguide substrate, wherein a main surface of the waveguide substrate includes a grating region and a non-grating region; A grating body is disposed in the grating region and has a top, a bottom, and a sidewall connecting the top and the bottom; and An optical coating, covering at least a portion of the non-grating area and the grating body, is used to reduce reflection of external light. The optical coating includes a first coating and a second coating covering the first coating, wherein the effective refractive index n of the first coating is... e1 The effective refractive index n of the second coating e2 All are lower than the refractive index of the grating body; In at least a portion of the non-grating region, the second coating overlaps with the first coating; and On the grating body, the first coating covers only the top, and the second coating covers at least the top and bottom.

2. The optical waveguide device as described in claim 1, wherein, The effective refractive index n of the first coating e1 Within the range of 1.3-2, the effective refractive index n of the second coating is... e2 Within the range of 1.3-2.

3. The optical waveguide device as described in claim 2, wherein, The thickness H1 of the first coating on the top of the grating body and the thickness H2 of the second coating on the top of the grating body satisfy: 50nm≤H1+H2≤120nm, and 20nm≤H2≤100nm.

4. The optical waveguide device as described in claim 3, wherein, 15nm≤H1≤70nm.

5. The optical waveguide device as described in claim 1, wherein, The refractive index of each material in the first coating is in the range of 1.3-1.7, and the refractive index of each material in the second coating is in the range of 1.3-2; and The thickness H1 of the first coating on the top of the grating body and the thickness H2 of the second coating on the top of the grating body satisfy: 60nm≤H1+H2≤120nm, 15nm≤H1≤60nm, and 20nm≤H2≤100nm.

6. The optical waveguide device as described in claim 5, wherein, The first coating and the second coating each consist of only one film layer.

7. The optical waveguide device according to any one of claims 1-6, wherein, The first coating comprises a first material, and the second coating comprises a second material, wherein the first material and the second material have different refractive indices.

8. The optical waveguide device according to any one of claims 1-6, wherein, The thickness H2 of the second coating on the top of the grating body and the thickness D2 of the second coating on the bottom of the grating body satisfy: D2≤H2.

9. The optical waveguide device as described in claim 8, wherein, D2 ≥ H2 / 3 or D2 ≥ 15nm.

10. The optical waveguide device as described in claim 8 or 9, wherein, The second coating also covers the sidewall of the grating body, and has an average thickness of W2 on the sidewall, where W2 ≤ D2.

11. The optical waveguide device as claimed in claim 10, wherein, W2≥H2 / 3 or W2≥15nm.

12. The optical waveguide device as described in claim 8 or 9, wherein, The sidewalls include a first sidewall and a second sidewall that are opposite to each other, and the first sidewall forms a first angle θ1 with the bottom that is greater than 90°. o The second included angle θ2 formed by the second sidewall and the bottom is smaller than the first included angle θ1; wherein preferably, the thickness W of the second coating on the first sidewall is... 21 and the thickness W on the second sidewall 22 Satisfy: W 22 ≤W 21 And H2 / 3≤W 21 ≤D2≤H2.

13. The optical waveguide device according to any one of claims 1-12, wherein, The refractive index difference between any two adjacent film layers with a thickness of not less than 15 nm in the optical coating is less than 0.5, preferably less than 0.

3.

14. The optical waveguide device according to any one of claims 1-12, wherein, The top of the grating body has a stepped shape, and the first coating covers at least the surface of the highest step of the stepped shape.

15. The optical waveguide device according to any one of claims 1-14, wherein, The grating body is configured to diffract a portion of the light propagating in the waveguide substrate along a first direction via total internal reflection at a predetermined order, causing it to exit the grating body in a second direction different from the first direction, while allowing another portion of the light to continue propagating along the first direction via total internal reflection; and The grating body includes at least two regions with different grating duty cycles.

16. The optical waveguide device as claimed in claim 15, wherein, The grating body is a folding grating or a coupling grating, and the grating duty cycle in different regions of the grating body varies between 0.3 and 0.

7.

17. A display device comprising an optical waveguide device as claimed in any one of claims 1-16.

18. The display device as claimed in claim 17, wherein, The display device is a near-eye display device and also includes a lens and a frame for holding the lens close to the eye, the lens including the optical waveguide device.

19. A method for manufacturing an optical waveguide device, comprising the following steps: (1) Provide waveguide substrate; (2) Apply a grating material to a main surface of the waveguide substrate, the main surface including a first region and a second region other than the first region; (3) Deposit a first coating to cover the first region and at least a portion of the second region, and make the effective refractive index n of the first coating... e1 The refractive index is lower than that of the grating material; (4) Etching is performed in the first region to remove the first coating and a portion of the grating material; as well as (5) Deposit a second coating to cover the first region and at least a portion of the second region, and such that the effective refractive index n of the second coating is such that... e2 The refractive index is lower than that of the grating material.

20. The method of claim 19, further comprising: Between steps (2) and (3), pre-etching is performed in the first region to remove a portion of the grating material to form a top surface of a predetermined shape.

21. The method of claim 19, further comprising: Between steps (4) and (5), supplementary etching is performed in the first region to remove a portion of the grating material or to remove a portion of the first coating and the grating material.

22. The method of claim 19, wherein, The refractive index of each material in the first coating is in the range of 1.3-1.7, and the refractive index of each material in the second coating is in the range of 1.3-2; and The thickness H1 of the first coating and the thickness H2 of the portion of the second coating covering the first coating satisfy: 60nm≤H1+H2≤120nm, 15nm≤H1≤60nm, and 20nm≤H2≤100nm.

23. The method of claim 22, wherein, The first coating and the second coating each consist of only one film layer.

24. The method according to any one of claims 19-23, wherein, Step (5) includes depositing a second coating using an isotropic or anisotropic process, such that the thickness H2 of the second coating on the first coating, the thickness D2 on the bottom formed by etching of the grating material, and the average thickness W2 on the sidewall formed by etching of the grating material satisfy: H2 / 3≤W2≤D2≤H2.

25. The method according to any one of claims 19-23, wherein, The sidewalls formed by etching the grating material include a first sidewall and a second sidewall that are opposite to each other, and the first sidewall forms a first angle θ1 with the bottom that is greater than 90°. o The second included angle θ2 formed by the second sidewall and the bottom is smaller than the first included angle θ1; wherein preferably, step (5) includes depositing a second coating using an isotropic or anisotropic process, such that the thickness H2 of the second coating on the first coating, the thickness D2 on the bottom formed by etching the grating material, and the thickness W of the first sidewall are all greater than the thickness H2 of the second coating on the first coating. 21 and the thickness W on the second sidewall 22 Satisfy: W 22 ≤W 21 And H2 / 3≤W 21 ≤D2≤H2.

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