Diffractive optical waveguide and preparation method thereof, and display device

Abstract

The present invention discloses a diffraction optical waveguide and a preparation method thereof, and a display device, and relates to the technical field of diffraction optical waveguides, wherein the diffraction optical waveguide comprises a substrate and an asymmetric grating arranged on the substrate, the asymmetric grating comprises at least one asymmetric grating periodic unit, each asymmetric grating periodic unit comprises a first grating periodic structure and a second grating periodic structure whose cross-sectional shapes are symmetrical about the grating axis plane, the second grating periodic structure comprises a first main body portion arranged on a first side surface of the first grating periodic structure, a second main body portion arranged on a top surface of the first grating periodic structure, and a third main body portion transitionally connected between the first main body portion and the second main body portion; a side surface of the second main body portion away from the first grating periodic structure is a first inclined surface, the first inclined surface extends in a direction away from the substrate, and is inclinedly arranged in a direction away from the first grating periodic structure; the technical solution of the present invention can provide a diffraction optical waveguide with high optical efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of diffraction optical waveguides, and in particular to a diffraction optical waveguide and a preparation method thereof, and a display device. Background Art

[0002] In the related art, common diffraction waveguides usually use symmetrical grating structures, such as common rectangular or sinusoidal shapes. In application, most of the diffraction light energy of such diffraction waveguides is usually concentrated in the 0th order, while the average diffraction efficiency of other energy levels such as ±1st order is not high, resulting in low effective coupling energy of the entrance pupil in the diffraction waveguide, and the overall optical efficiency of the diffraction waveguide is not high, which is difficult to meet the actual use requirements. Summary of the invention

[0003] The main purpose of the present invention is to provide a diffractive optical waveguide and a preparation method thereof, and a display device, aiming to provide a diffractive optical waveguide with high optical efficiency.

[0004] To achieve the above-mentioned object, the diffraction optical waveguide proposed in the present invention comprises a substrate and an asymmetric grating arranged on the substrate, wherein the asymmetric grating comprises at least one asymmetric grating periodic unit; each of the asymmetric grating periodic units comprises a first grating periodic structure whose cross-sectional shape is symmetrical about the grating axis plane, and also comprises a second grating periodic structure stacked on the first grating periodic structure, wherein the second grating periodic structure comprises:

[0005] A first main body portion, the first main body portion is disposed on a first side surface of the first grating periodic structure;

[0006] a second main body portion, the second main body portion being disposed on a top surface of the first grating periodic structure; and

[0007] a third main body portion, the third main body portion being transitionally connected between the second main body portion and the first main body portion;

[0008] A surface of the first main body portion on one side away from the first grating periodic structure is a first inclined surface. The first inclined surface extends in a direction away from the substrate and is inclined in a direction away from the first grating periodic structure.

[0009] In one embodiment, the first inclined surface is configured as a curved surface or a flat surface;

[0010] And / or, the angle between the first inclined surface and the surface of the substrate is in the range of 60° to 90°;

[0011] And / or, a minimum width of the first main body in an arrangement direction of the first main body and the first grating periodic structure ranges from 10 nm to 100 nm.

[0012] In one embodiment, a surface of the second main body portion facing away from the third main body portion is a second inclined surface, and the second inclined surface extends in a direction away from the first grating periodic structure and is inclined toward the third main body portion.

[0013] In one embodiment, the second inclined surface is configured as a curved surface or a flat surface;

[0014] And / or, the angle between the second inclined surface and the top surface of the first grating periodic structure is in the range of 40° to 90°;

[0015] And / or, the top surface of the second main body is arranged parallel to the top surface of the first grating periodic structure, and the vertical distance from the top surface of the second main body to the top surface of the first grating periodic structure is defined as the thickness dc of the second main body, and the vertical distance from the top surface of the first grating periodic structure to the substrate surface is defined as the thickness dg of the first grating periodic structure, wherein dc=dg.

[0016] In one embodiment, a width of a top surface of the second grating periodic structure is greater than a width of the first grating periodic structure.

[0017] In one embodiment, the difference in refractive index between the second grating periodic structure and the first grating periodic structure is greater than 0.2.

[0018] In one embodiment, the refractive index of the substrate ranges from 1.6 to 2.1;

[0019] And / or, the grating period of the first grating periodic structure ranges from 350nm to 700nm;

[0020] And / or, the duty cycle of the first grating periodic structure is in the range of 0.2 to 0.7;

[0021] And / or, the refractive index of the first grating periodic structure is in the range of 1.6 to 2.1;

[0022] And / or, a vertical distance from a top surface of the second main body to a top surface of the first grating periodic structure is a thickness dc of the second main body, and the thickness dc of the second main body is in a range of 40 nm to 300 nm;

[0023] And / or, a vertical distance from the top surface of the first grating periodic structure to the surface of the substrate is a thickness dg of the first grating periodic structure, and the thickness dg of the first grating periodic structure is in a range of 50 nm to 300 nm;

[0024] And / or, the refractive index of the second grating periodic structure is in the range of 1.9 to 3.5.

[0025] In one embodiment, the asymmetric grating periodic unit further includes a third grating periodic structure, wherein one end of the third grating periodic structure facing the substrate is arranged on the second side surface of the first grating periodic structure, and the other end of the third grating periodic structure extends toward the top surface of the second grating periodic structure and is superimposed on the top surface of the second grating periodic structure, and the third grating periodic structure and the second grating periodic structure have different refractive indices.

[0026] In one embodiment, the difference in refractive index between the second grating periodic structure and the third grating periodic structure is greater than 0.1;

[0027] And / or, a difference in refractive index between one of the second grating periodic structure and the third grating periodic structure and the first grating periodic structure is greater than 0.2.

[0028] In one embodiment, one end of the second grating periodic structure facing the substrate is connected to the substrate surface, and one end of the third grating periodic structure facing the substrate is connected to the substrate surface.

[0029] In one embodiment, the asymmetric grating periodic unit further comprises a multi-level grating periodic structure, and the multi-level grating periodic structure is stacked on the second grating periodic structure;

[0030] Wherein, one end of the first-stage grating periodic structure in the multi-stage grating periodic structure is arranged on the first inclined surface, and the other end extends toward the top surface of the second grating periodic structure and is overlapped on the top surface of the second grating periodic structure;

[0031] One end of the next grating periodic structure in the multi-level grating periodic structure is arranged on a side surface of the previous grating periodic structure away from the first main body, and the other end extends toward the top surface of the previous grating periodic structure and is overlapped on the top surface of the previous grating periodic structure.

[0032] In one embodiment, one end of the second grating periodic structure facing the substrate is connected to the substrate surface;

[0033] Each grating periodic structure in the multi-stage grating periodic structure is spaced apart from the substrate surface at one end facing the substrate, and the spacing between the subsequent grating periodic structure and the substrate surface is greater than the spacing between the previous grating periodic structure and the substrate surface.

[0034] In one embodiment, each level of the multi-level grating periodic structure has a first surface and a second surface that are arranged opposite to each other in a direction from the first main body to the first grating periodic structure;

[0035] The included angle between each of the first surfaces and the base surface is equal to the included angle between the first inclined surface and the base surface;

[0036] And / or, a side surface of the second main body portion facing away from the third main body portion is defined as a second inclined surface, and an angle between each of the second surfaces and the base surface is equal to an angle between the second inclined surface and the base surface.

[0037] In one embodiment, the difference in refractive index between the second grating periodic structure or at least one of the multi-stage grating periodic structure and the first grating periodic structure is greater than 0.2;

[0038] And / or, the difference in refractive index between the first-level grating periodic structure and the second-level grating periodic structure is greater than 0.1, and the difference in refractive index between two adjacent levels of grating periodic structures in the multi-level grating periodic structure is greater than 0.1.

[0039] The present invention further provides a method for preparing the diffractive optical waveguide as described in any one of the above, the method comprising the following steps:

[0040] Coating nanoimprint glue on the imprint mask and / or the substrate of the diffractive optical waveguide to make the imprint mask and the substrate fit together;

[0041] Curing the nanoimprint glue to prepare a first grating periodic structure of at least one asymmetric grating periodic unit on a surface of one side of the substrate;

[0042] The first grating periodic structure is subjected to an inclined coating process to obtain a second grating periodic structure by coating the surface of the first grating periodic structure.

[0043] The present invention further provides a display device, comprising any of the above-mentioned diffractive optical waveguides, wherein the diffractive optical waveguide comprises a substrate and an asymmetric grating disposed on the substrate, wherein the asymmetric grating comprises at least one asymmetric grating periodic unit; each of the asymmetric grating periodic units comprises a first grating periodic structure whose cross-sectional shape is symmetrical about the grating axis plane, and further comprises a second grating periodic structure stacked on the first grating periodic structure, wherein the second grating periodic structure comprises:

[0044] A first main body portion, the first main body portion is disposed on a first side surface of the first grating periodic structure;

[0045] a second main body portion, the second main body portion being disposed on a top surface of the first grating periodic structure; and

[0046] a third main body portion, the third main body portion being transitionally connected between the second main body portion and the first main body portion;

[0047] A surface of the first main body portion on one side away from the first grating periodic structure is a first inclined surface. The first inclined surface extends in a direction away from the substrate and is inclined in a direction away from the first grating periodic structure.

[0048] The diffraction optical waveguide of the technical solution of the present invention comprises a substrate and an asymmetric grating arranged on a side surface of the substrate, wherein the asymmetric grating comprises at least one asymmetric grating periodic unit, and each asymmetric grating periodic unit comprises a first grating periodic structure and a second grating periodic structure stacked on the first grating periodic structure. The cross-sectional shape of the first grating periodic structure is symmetrically arranged with respect to the grating axial plane. The second grating periodic structure comprises a first main body portion arranged on the first side surface of the first grating period, a second main body portion arranged on the top surface of the first grating periodic structure, and a third main body portion transitionally connected between the first main body portion and the second main body portion. Therefore, a second grating periodic structure with a cross-sectional shape asymmetrically arranged with respect to the grating axial plane can be obtained, and then an asymmetric grating periodic unit asymmetrically arranged with respect to the grating axial plane can be formed by combining the first grating periodic structure and the second grating periodic structure. On this basis, by setting the side surface of the first main body away from the first grating periodic structure as a first inclined surface, and making the first inclined surface extend in the direction away from the substrate, and being inclined in the direction away from the first grating periodic structure, the inclination degree of the second grating periodic structure as a whole toward the first side of the first grating periodic structure can be increased, thereby effectively increasing the overall asymmetry degree of the asymmetric grating periodic unit. By controlling the overall asymmetry degree of the asymmetric grating periodic unit, it is beneficial to concentrate the diffraction energy of the diffraction light waveguide to the non-zero energy level, thereby increasing the average diffraction efficiency of the non-zero energy level such as ±1 level, so as to increase the effective coupling energy of the entrance pupil in the diffraction light waveguide, thereby improving the optical efficiency of the diffraction light waveguide. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0050] Figure 1 A schematic structural diagram of a first embodiment of a diffractive optical waveguide provided by the present invention;

[0051] Figure 2 for Figure 1 The local structure diagram of the medium diffraction optical waveguide;

[0052] Figure 3 A partial structural diagram of a second embodiment of a diffractive optical waveguide provided by the present invention;

[0053] Figure 4 A partial structural diagram of a third embodiment of a diffractive optical waveguide provided by the present invention;

[0054] Figure 5 A partial structural diagram of a fourth embodiment of a diffractive optical waveguide provided by the present invention;

[0055] Figure 6 for Figure 1 The -1 diffraction order energy distribution diagram of the medium diffraction waveguide under different polarization conditions when the incident light is 450nm;

[0056] Figure 7 for Figure 1 The -1 diffraction order energy distribution diagram of the medium diffraction waveguide under different polarization conditions when the incident light is 460nm;

[0057] Figure 8 for Figure 1 The -1 diffraction order energy distribution diagram of the medium diffraction waveguide under different polarization conditions when the incident light is 470nm;

[0058] Fig. 9 for Figure 1 The -1 diffraction order energy distribution diagram of the medium diffraction waveguide under different polarization conditions when the incident light is 510nm;

[0059] Fig.10 for Figure 1 Energy distribution diagram of -1 diffraction order of medium diffraction waveguide under different polarization when the incident light is 610nm.

[0060] Description of Figure Numbers

[0061] 100, diffraction optical waveguide; 10, substrate; 20, asymmetric grating period unit; 21, first grating period structure; 22, second grating period structure; 221, first main body; 221a, first inclined surface; 222, second main body; 222a, second inclined surface; 223, third main body; 23, third grating period structure; 24, multi-level grating period structure; 24a, first level grating period structure; 24b, second level grating period structure.

[0062] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0063] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0064] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture. If the specific posture changes, the directional indication will also change accordingly.

[0065] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features limited to "first" and "second" may explicitly or implicitly include at least one of the features. In addition, if "and / or" or "and / or" appears in the full text, its meaning includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, solution B, or solutions that satisfy both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0066] In the related art, common diffraction waveguides usually use symmetrical grating structures, such as common rectangular or sinusoidal shapes. In application, most of the diffraction light energy of such diffraction waveguides is usually concentrated in the 0th order, while the average diffraction efficiency of other energy levels such as ±1st order is not high, resulting in low effective coupling energy of the entrance pupil in the diffraction waveguide, and the overall optical efficiency of the diffraction waveguide is not high, which is difficult to meet the actual use requirements.

[0067] The present invention provides a diffractive optical waveguide 100 .

[0068] See also Figures 1 to 5 In one embodiment of the present invention, the diffraction optical waveguide 100 includes a substrate 10 and an asymmetric grating arranged on the substrate 10, the asymmetric grating includes at least one asymmetric grating periodic unit 20; each asymmetric grating periodic unit 20 includes a first grating periodic structure 21 whose cross-sectional shape is symmetrical about the grating axis plane, and also includes a second grating periodic structure 22 stacked on the first grating periodic structure 21.

[0069] The substrate is also called a dielectric optical waveguide, which is generally planar, and the asymmetric grating is disposed on one of the outer surfaces of the substrate 10. The asymmetric grating may include a plurality of asymmetric grating periodic units 20, and the plurality of asymmetric grating periodic units 20 are arrayed on one side surface of the substrate 10 to form the asymmetric grating on the substrate 10. The substrate 10 is made of a high refractive index glass material, the first grating periodic structure 21 may be formed by curing a nanoimprint glue having a refractive index similar to or consistent with that of the substrate 10, but is not limited to, and the second grating periodic structure 22 may be formed by coating on the surface of the first grating periodic structure 21 through an oblique coating process, so that an asymmetric grating periodic unit 20 may be formed by stacking the first grating periodic structure 21 and the second grating periodic structure 22.

[0070] Specifically, the plane that is defined as the normal direction of the surface of the substrate 10 and parallel to the diffraction direction of the first grating periodic structure 21 is the grating axis plane. The first grating periodic structure 21 can be set as a rectangular grating, whose cross-sectional shape is rectangular, and there is a certain grating axis plane so that the cross-sectional shape of the rectangular grating is symmetrically arranged about the grating axis plane. In some embodiments, the first grating periodic structure 21 can also be set as other common symmetrical grating structures, such as a sinusoidal grating, which is not limited here.

[0071] For further information, see Figure 2 In an embodiment of the present invention, the second grating periodic structure 22 comprises:

[0072] A first main body portion 221, which is disposed on a first side surface of the first grating periodic structure 21;

[0073] a second main body portion 222 , which is disposed on the top surface of the first grating periodic structure 21 ; and

[0074] The third main body portion 223 is transitionally connected between the second main body portion 222 and the first main body portion 221 .

[0075] One of the two opposite sides of the first grating periodic structure 21 along its periodic arrangement direction is defined as its first side surface, and the other side is defined as its second side surface. By arranging the first main body 221 on the first side surface of the first grating periodic structure 21 and arranging the second main body 222 on the top of the first grating periodic structure 21, the second grating periodic structure 22 can be arranged asymmetrically with respect to the grating axis plane.

[0076] By providing the third main body 223, the second main body 222 and the first main body 221 can be connected as one, so that the second grating periodic structure 22 of the asymmetric grating periodic unit 20 can be plated on the first grating periodic structure 21 of the asymmetric grating periodic unit 20 at one time through an inclined coating process.

[0077] The third main body 223 is smoothly transitioned with the first main body 221 and the second main body 222. Figure 1 and Figure 2 In the first embodiment of the diffractive optical waveguide 100 of the present invention shown in FIG. 1 , the surface of the second main body portion 222 away from the first grating periodic structure 21 and the surface of the third main body portion 223 away from the first main body portion 221 are both planes, and the two planes are arranged flush with each other to connect to form a continuous plane; the surface of the first main body portion 221 away from the first grating periodic structure 21 and the surface of the third main body portion 223 away from the second main body portion 222 are also both planes, and the two planes are arranged flush with each other to connect to form a continuous plane.

[0078] Of course, the technical solution of the present invention is not limited to this. Figure 3 In the second embodiment of the diffractive optical waveguide 100 of the present invention shown in FIG. 1 , the surface of the second main body 222 away from the first grating periodic structure 21 and the surface of the third main body 223 away from the first main body 221 are both arc surfaces, and the two can be connected to form a continuous arc surface; the surface of the first main body 221 away from the first grating periodic structure 21 and the surface of the third main body 223 away from the second main body 222 are also arc surfaces, and can also be connected to form a continuous arc surface. The specific implementation method can be set according to actual needs and is not limited here.

[0079] Further, in the embodiment of the present invention, a side surface of the first main body 221 away from the first grating periodic structure 21 is a first inclined surface 221a, and the first inclined surface 221a extends in a direction away from the substrate 10, and is inclined in a direction away from the first grating periodic structure 21. In this way, the second grating periodic structure 22 can be more inclined toward the first side of the first grating periodic structure 21 as a whole, thereby effectively increasing the overall asymmetry of the asymmetric grating periodic unit 20.

[0080] It can be understood that by controlling the overall asymmetry of the asymmetric grating periodic unit 20, it is beneficial to concentrate the diffraction energy of the diffraction optical waveguide 100 to the non-zero energy level, thereby increasing the average diffraction efficiency of the non-zero energy level such as ±1 level, so as to increase the effective coupling energy of the entrance pupil in the diffraction optical waveguide 100, thereby improving the optical efficiency of the diffraction optical waveguide 100.

[0081] In the embodiment of the present invention, the first inclined surface 221 a is a curved surface or a flat surface.

[0082] The first inclined surface 221a may be as follows: Figure 3 to Figure 4The curved surface shown in the figure can make the profile of the surface of this part gradually become nonlinear, which is conducive to further increasing the asymmetry of the asymmetric grating periodic unit 20. In addition, this structural setting is more in line with the effect of directly coating the second grating periodic structure 22 by the film forming process, which can reduce the difficulty of preparing the asymmetric grating. Of course, the surface of the first main body 221 away from the first grating periodic structure 21 can also be as Figure 1 , Figure 2 as well as Figure 5 The specific implementation method can be set according to actual needs and is not limited here.

[0083] See also Figure 2 In the embodiment of the present invention, the angle between the first inclined surface 221a and the surface of the substrate 10 is in the range of 60° to 90°.

[0084] Specifically, the asymmetric grating periodic unit 20 is provided with a first grating periodic structure 21 and a second grating periodic structure 22, wherein a first main body 221 of the second grating periodic structure 22 directly covers a first side surface of the first grating periodic structure 21, and an angle θ1 between a first inclined surface 221a of the first main body 221 of the second grating periodic structure 22 away from the first grating periodic structure 21 and a top surface of the substrate 10 of the diffractive optical waveguide 100 is in a range of 60° to 90°, for example, 60°, 70°, 80°, 90° and any value between 60° and 90°. In this way, the inclination of the first main body 221 can be limited, so as to facilitate the diffractive optical waveguide 100 to maintain uniformity of energy distribution while increasing the intensity of diffracted light of a specific order.

[0085] In an embodiment of the present invention, Figure 2 The first embodiment of the diffractive optical waveguide 100 shown in FIG. Figure 3 As shown in the second embodiment of the diffraction optical waveguide 100, in the arrangement direction of the first main body 221 and the first grating periodic structure 21, the width of the first main body 221 is gradually increased in the direction away from the substrate 10 of the diffraction optical waveguide 100, that is, the width of the first main body 221 toward one end of the diffraction optical waveguide 100 is its minimum width wc.

[0086] Further, the minimum width wc of the first main body 221 in the arrangement direction of the first main body 221 and the first grating periodic structure 21 ranges from 10nm to 100nm. For example, the minimum width wc can be set to 10nm, 40nm, 70nm, 100nm, and any value between 10nm and 100nm.

[0087] See also Figure 1 and Figure 2In the embodiment of the present invention, a side surface of the second main body 222 away from the third main body 223 is a second inclined surface 222a, and the second inclined surface 222a extends in a direction away from the first grating periodic structure 21, and is inclined toward the third main body 223. In this way, the second grating periodic structure 22 can be tilted more toward the first side of the first grating periodic structure 21 as a whole, thereby effectively increasing the overall asymmetry of the asymmetric grating periodic unit 20, which is conducive to completely concentrating the diffraction energy to a certain energy level, thereby effectively increasing the diffraction effect of a specific order of light.

[0088] See also Figures 1 to 6 In the embodiment of the present invention, the second inclined surface 222a is configured as an arc surface or a plane.

[0089] The second inclined surface 222a is configured as an arc surface, which can make the profile of this part of the surface gradually become nonlinear, which is conducive to further increasing the asymmetry of the asymmetric grating periodic unit 20. In addition, this structural configuration is more in line with the effect of directly coating the second grating periodic structure 22 by the film forming process, which can reduce the difficulty of preparing the asymmetric grating. Of course, the surface of the second main body 222 away from the third main body 223 can also be as Figure 1 , Figure 2 as well as Figure 5 The specific implementation method can be set according to actual needs and is not limited here.

[0090] See also Figure 2 In the embodiment of the present invention, the angle between the second inclined surface 222a and the top surface of the first grating periodic structure 21 is in the range of 40° to 90°.

[0091] Specifically, the asymmetric grating periodic unit 20 is provided with a first grating periodic structure 21 and at least one second grating periodic structure 22, the second main body 222 of the second grating periodic structure 22 directly covers the top surface of the first grating periodic structure 21, and the angle θ2 between the second inclined surface 222a of the second main body 222 of the second grating periodic structure 22 away from the third main body 223 and the top surface of the first grating periodic structure 21 is in the range of 40° to 90°, for example, 40°, 50°, 60°, 70°, 80°, 90° and any value between 40° and 90°. In this way, the inclination of the second main body 222 can be limited, so as to facilitate the diffraction optical waveguide 100 to maintain the uniformity of energy distribution while increasing the diffraction light intensity of a specific order.

[0092] See also Figure 2In the embodiment of the present invention, in the arrangement direction of the first main body 221 and the first grating periodic structure 21, the top surface of the second main body 222 is arranged parallel to the top surface of the first grating periodic structure 21, and the vertical distance from the top surface of the second main body 222 to the top surface of the first grating periodic structure 21 is defined as the thickness dc of the second main body 222, and the vertical distance from the top surface of the first grating periodic structure 21 to the surface of the substrate 10 is defined as the thickness dg of the first grating periodic structure 21, wherein dc=dg. That is, the thickness dc of the second main body 222 can be equal to or similar to the thickness dg of the first grating periodic structure 21.

[0093] In the embodiment of the present invention, the thickness dc of the first grating periodic structure 21 ranges from 40 nm to 300 nm. For example, the thickness dc can be 40 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, or any value between 40 nm and 300 nm.

[0094] In the embodiment of the present invention, the refractive index of the substrate 10 is in the range of 1.6 to 2.1. For example, the refractive index of the substrate 10 can be 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, or any value between 1.6 and 2.1. The specific material of the substrate 10 can be, but is not limited to, nanoimprint glue.

[0095] In the embodiment of the present invention, the grating period of the first grating periodic structure 21 ranges from 350nm to 700nm. For example, the grating period of the first grating periodic structure 21 can be 350nm, 400nm, 450nm, 500nm, 550nm, 600nm, 650nm, 700nm, and any value between 350nm and 700nm. By controlling the grating period of the first grating periodic structure 21, the wavelength band of the incident light adapted by the asymmetric diffraction optical waveguide 100 can be adjusted.

[0096] In the embodiment of the present invention, the duty cycle of the first grating periodic structure 21 ranges from 0.2 to 0.7. For example, the duty cycle of the first grating periodic structure 21 can be 0.2, 0.4, 0.6, 0.7, or any value between 0.2 and 0.7.

[0097] The grating width of the first grating periodic structure 21 is the product of the grating period of the first grating periodic structure 21 and its grating duty cycle. By controlling the grating period and duty cycle parameters of the first grating periodic structure 21, the width value of the first grating periodic structure 21 in its periodic arrangement direction can be controlled.

[0098] In an embodiment of the present invention, the refractive index of the first grating periodic structure 21 is in the range of 1.6 to 2.1. For example, the refractive index of the first grating periodic structure 21 can be 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, and any value between 1.6 and 2.1. The specific material of the first grating periodic structure 21 can be, but is not limited to, nanoimprint glue.

[0099] In the embodiment of the present invention, the vertical distance from the top surface of the first grating periodic structure 21 to the surface of the substrate 10 is the thickness dg of the first grating periodic structure 21, and the thickness dg of the first grating periodic structure 21 ranges from 50nm to 300nm. For example, the thickness dg can be 50nm, 100nm, 150nm, 200nm, 250nm, 300nm, and any value between 50nm and 300nm.

[0100] In the embodiment of the present invention, the width wt of the top surface of the second grating periodic structure 22 is greater than the width of the first grating periodic structure 21. This is beneficial to increase the overall asymmetry of the asymmetric grating periodic unit 20. The width of the first grating periodic structure 21 is the product of the grating period of the first grating periodic structure 21 and its duty cycle.

[0101] In an embodiment of the present invention, the refractive index of the second grating periodic structure 22 is in the range of 1.9 to 3.5. For example, the refractive index of the second grating periodic structure 22 can be 1.9, 2.5, 3.0, 3.5, or any value between 1.9 and 3.5. The second grating periodic structure 22 has a high refractive index relative to the first grating periodic structure 21, and its specific material can be, but is not limited to, an inorganic material, an organic material, a metal material, or a composite stacked layer of any of the foregoing materials.

[0102] Further, in an embodiment of the present invention, the difference in refractive index between the second grating periodic structure 22 and the first grating periodic structure 21 is greater than 0.2. By setting the material of the second grating periodic structure 22 to a high refractive index material and forming a certain refractive index difference between the first grating periodic structure 21 and the second grating periodic structure 22, it is beneficial to achieve different optical control requirements by controlling the refractive index of the second grating periodic structure 22 and the first grating periodic structure 21.

[0103] See also Figure 4 In an embodiment of the present invention, the asymmetric grating periodic unit 20 further includes a third grating periodic structure 23, wherein one end of the third grating periodic structure 23 facing the substrate 10 is arranged on the second side surface of the first grating periodic structure 21, and the other end extends toward the top surface of the second grating periodic structure 22 and is stacked on the top surface of the second grating periodic structure 22, and the refractive index of the third grating periodic structure 23 and the second grating periodic structure 22 are different.

[0104] The third grating periodic structure 23 has the same or similar structure as the second grating periodic structure 22, and the specific structural parameters can refer to the second grating periodic structure 22 in the aforementioned embodiment. In addition, the third grating periodic structure 23 and the second grating periodic structure 22 are made of different materials, and at least one of them is a high refractive index material, so that there is a refractive index difference between the second grating periodic structure 22 and the third grating periodic structure 23, thereby further optimizing the optical effect of the asymmetric grating.

[0105] In the embodiment of the present invention, the difference in refractive index between the second grating periodic structure 22 and the third grating periodic structure 23 is greater than 0.1. In this way, the optical control effect of the asymmetric grating periodic unit 20 can be improved by the difference in refractive index between the second grating periodic structure 22 and the third grating periodic structure 23, so as to optimize the optical performance of the diffraction optical waveguide, such as the diffraction efficiency.

[0106] In an embodiment of the present invention, the difference in refractive index between one of the second grating periodic structure 22 and the third grating periodic structure 23 and the first grating periodic structure 21 is greater than 0.2. In this way, the optical control effect of the asymmetric grating periodic unit 20 can be guaranteed.

[0107] Specifically, in a feasible implementation, the refractive index of the second grating periodic structure 22 may be the same as the refractive index of the first grating periodic structure 21 , and the refractive index of the third grating periodic structure 23 is higher than the refractive indexes of the second grating periodic structure 22 and the first grating periodic structure 21 .

[0108] In another feasible implementation, the refractive index of the second grating periodic structure 22 is higher than the refractive index of the first grating periodic structure 21, and the refractive index of the third grating periodic structure 23 may be higher than the refractive index of the first grating periodic structure 21, or may be lower than the refractive index of the first grating periodic structure 21. Furthermore, when the refractive index of the third grating periodic structure 23 is lower than the refractive index of the first grating periodic structure 21, the refractive index of the third grating periodic structure 23 may also be the same as the refractive index of the first grating periodic structure 21, which is not limited here. With such a configuration, the refractive indices of the second grating periodic structure 22 and the third grating periodic structure 23 may be flexibly controlled to achieve different optical regulation requirements.

[0109] Further, in some embodiments, one end of the second grating periodic structure 22 facing the substrate 10 is connected to the surface of the substrate 10, and one end of the third grating periodic structure 23 facing the substrate 10 is connected to the surface of the substrate 10. Such an arrangement is conducive to improving the structural stability of the second grating periodic structure 22 and the third grating periodic structure 23.

[0110] See also Figure 5In an embodiment of the present invention, the asymmetric grating periodic unit 20 further includes a multi-level grating periodic structure 24, and the multi-level grating periodic structure 24 is stacked on the second grating periodic structure 22;

[0111] Among them, one end of the first-stage grating periodic structure 24a in the multi-stage grating periodic structure 24 is arranged on the first inclined surface 221a, and the other end extends toward the top surface of the second grating periodic structure 22 and is overlapped on the top surface of the second grating periodic structure 22;

[0112] One end of the next grating periodic structure in the multi-stage grating periodic structure 24 is arranged on a side surface of the previous grating periodic structure away from the first main body 221, and the other end extends toward the top surface of the previous grating periodic structure and is overlapped on the top surface of the previous grating periodic structure.

[0113] In this way, the multi-level grating periodic structure 24 can be stacked step by step along the direction from the first grating periodic structure 21 to the first main body 221 in the direction away from the substrate, thereby making the asymmetric grating periodic unit 20 as a whole more inclined toward the first side of its first grating periodic structure 21.

[0114] Each level of the grating periodic structure in the multi-level grating periodic structure 24 can be set to a different material so that there is a refractive index difference between the next level of the grating periodic structure and the previous level of the grating periodic structure. In this way, different optical control requirements can be achieved by flexibly controlling the refractive index of each level of the grating periodic structure in the multi-level grating periodic structure 24.

[0115] Specifically, the multi-level grating periodic structure 24 may include at least a first-level grating periodic structure 24a and a second-level grating periodic structure 24b. The refractive indexes of the second grating periodic structure 22, the first-level grating periodic structure 24a and the second-level grating periodic structure 24b may be set to increase in sequence relative to the first grating periodic structure 21; or the refractive index of one of the second grating periodic structure 22, the first-level grating periodic structure 24a and the second-level grating periodic structure 24b may be greater than the first grating periodic structure 21, and the other two may be higher than the refractive index of the first grating periodic structure 21, or may be equal to or lower than the refractive index of the first grating periodic structure 21. The specific implementation method may be set according to actual needs and is not limited here.

[0116] In other embodiments, the multi-level grating periodic structure 24 may further include a third-level grating periodic structure, a fourth-level grating periodic structure, or even more levels of grating periodic structures sequentially stacked on the second-level grating periodic structure 24b. The specific number of levels of the grating periodic structure in the multi-level grating periodic structure 24 may be set according to actual needs and is not limited here.

[0117] Further, in some embodiments, one end of the second grating periodic structure 22 facing the substrate 10 is connected to the surface of the substrate 10;

[0118] Each grating periodic structure in the multi-level grating periodic structure 24 is spaced apart from the surface of the substrate 10 at one end thereof facing the substrate 10 , and the spacing between the subsequent grating periodic structure and the surface of the substrate 10 is greater than the spacing between the previous grating periodic structure and the surface of the substrate 10 .

[0119] Such an arrangement can facilitate the deposition and forming of the multi-level grating periodic structure 24 while improving the structural stability of the second grating periodic structure 22. Moreover, by making each level of the grating periodic structure in the multi-level grating periodic structure 24 spaced apart from the surface of the substrate 10 at one end facing the substrate 10, and by gradually increasing the spacing between each level of the grating periodic structure and the surface of the substrate 10 as the number of levels increases, the occupied volume and material cost of the multi-level grating periodic structure 24 can be reduced to a certain extent.

[0120] Furthermore, in some embodiments, each level of the multi-level grating periodic structure 24 has a first surface and a second surface that are arranged opposite to each other in a direction from the first main body 221 to the first grating periodic structure 21 .

[0121] Among them, the angle between each first surface and the surface of the substrate 10 is equal to the angle θ1 between the first inclined surface 221a and the surface of the substrate 10, and / or, the side surface of the second main body 222 away from the third main body 223 is defined as the second inclined surface 222a, and the angle between each second surface and the surface of the substrate 10 is equal to the angle θ2 between the second inclined surface 222a and the surface of the substrate 10.

[0122] In this way, each level of the multi-level grating periodic structure 24 can have an optical modulation performance similar to that of the second grating periodic structure 22. Furthermore, when the angle between each first surface and the surface of the substrate 10 is equal to the angle θ1 between the second inclined surface 222a and the surface of the substrate 10, the plurality of first surfaces and the second inclined surfaces 222a can be arranged flush with each other along the same straight line direction to be connected to form a continuous plane.

[0123] Further, in the embodiment of the present invention, the difference between the refractive index of the second grating periodic structure 22 or at least one of the multi-stage grating periodic structure 24 and the first grating periodic structure 21 is greater than 0.2. That is, among the other grating periodic structures stacked on the first grating periodic structure 21, at least one grating periodic structure has a difference between the refractive index of the first grating periodic structure 21 and the refractive index of the first grating periodic structure 21 greater than 0.2, thereby ensuring the overall optical control effect of the asymmetric grating periodic unit 20.

[0124] Further, in the embodiment of the present invention, the difference in refractive index between the first-stage grating periodic structure 24a and the second-stage grating periodic structure 22 is greater than 0.1, and the difference in refractive index between two adjacent stages of the multi-stage grating periodic structure 24 is greater than 0.1. That is, among the other grating periodic structures stacked on the first grating periodic structure 21, there is a refractive index difference greater than 0.1 between any two adjacent grating periodic structures, thereby achieving multiple optical adjustments to further optimize the optical performance of the diffraction optical waveguide 100, such as the diffraction efficiency.

[0125] The optical performance of the diffractive optical waveguide 100 proposed by the present invention will be described in the following specific embodiments:

[0126] See also Figure 2 , Figure 2 FIG. 1 is a partial structural diagram of a first embodiment of a diffractive optical waveguide 100 provided by the present invention.

[0127] In this embodiment, the grating period of the diffractive optical waveguide 100 is 450 nm, the grating height is 125 nm, the grating duty cycle is 0.45, the refractive index of the first grating periodic structure 21 of the asymmetric grating periodic unit 20 and the refractive index of the substrate 10 are 1.7, the refractive index of the second grating periodic structure 22 is 2.25, the thickness of the second main body 222 of the second grating periodic structure 22 is 125 nm, and the minimum width of the first main body 221 is 42 nm.

[0128] The diffraction optical waveguide 100 of this embodiment is optically simulated:

[0129] Figure 6 The figure shows the -1 diffraction order energy distribution diagram of the diffraction optical waveguide 100 of this embodiment under different polarizations. As shown in the figure, under the incidence of 450nm wavelength light, the diffraction optical waveguide 100 has a maximum diffraction efficiency of nearly 70% at the -1 order TE polarization, and its diffraction efficiency can reach 60% or more in a large range.

[0130] Furthermore, although the diffraction efficiency of the diffraction optical waveguide 100 at the -1 order TE polarization shows a gradually decreasing trend in the range of -20° to 20°, the diffraction efficiency of the -1 order TM polarization shows a gradually increasing trend, and the average diffraction efficiency of TE polarization is about 59%. It can be seen that when the energy of natural light is half of the sum of TE polarization and TM polarization, the average energy of the diffraction optical waveguide 100 at the -1 order can be kept close to 50% in the range of -20° to 20°.

[0131] It should be noted that in the related art, when the second main body 222, the first main body 221 and the third main body 223 in the second grating periodic structure 22 are arranged in a rectangular shape, a relatively more regular second grating periodic structure 22 can be provided. However, this solution can only achieve relatively uniform energy distribution under TM polarization, and the average diffraction efficiency is 53%. For the case under natural light, the diffraction efficiency of this solution will gradually decrease from 52% to 29%, that is, the diffraction energy distribution is uneven. Therefore, in order to achieve uniform energy coupling in such a structure, the natural light emitted by the display devices such as OLED, LED, etc. in the display device needs to be converted into polarized light, and the polarization conversion of light will lead to the loss of light energy, which has certain limitations.

[0132] As can be seen from the above optical simulation results, compared with this solution, the first embodiment of the diffractive optical waveguide 100 provided by the present invention does not need to have polarization dependence on the incident light source, and can achieve high-efficiency coupling by using natural light incident. Moreover, the diffraction efficiency of the diffractive optical waveguide 100 of this embodiment is improved by at least times compared with the diffraction efficiency of the traditional diffractive optical waveguide 100 structure.

[0133] For further information, see Figure 7 and Figure 8 , Figure 7 1 is an energy distribution diagram of the -1 diffraction order of the diffraction waveguide 100 of this embodiment under different polarizations when the incident light has a wavelength of 460 nm. It can be seen from the figure that when the incident light wavelength is 460 nm, the average energy of the diffraction waveguide 100 at the -1 order can be maintained at nearly 50% in the range of -20° to 20°. Figure 8 1 is an energy distribution diagram of the -1 diffraction order of the diffraction waveguide 100 of this embodiment under different polarizations when the incident light has a wavelength of 470 nm. It can be seen from the figure that when the incident light wavelength is 470 nm, the average energy of the diffraction waveguide 100 at the -1 order can be maintained at nearly 50% in the range of -20° to 20°.

[0134] It can be seen that when the wavelength range of the incident light is 450nm~470nm, the diffraction optical waveguide 100 of this embodiment can achieve a diffraction efficiency of nearly 50% within a field of view of at least 40°, that is, the corresponding incident light wavelength of this embodiment can cover the entire blue light band, so that the energy of the blue light band can be effectively coupled.

[0135] For further information, see Fig. 9 and Fig.10 , Fig. 93 is a diagram of the -1 diffraction order energy distribution under different polarizations when the grating period of the diffraction optical waveguide 100 of this embodiment is equal to 530nm. It can be seen that when the grating period of the diffraction optical waveguide 100 is equal to 530nm, the incident light wavelength corresponding to the optical waveguide of this embodiment can cover the green light band. Fig.10 1 is an energy distribution diagram of the -1 diffraction order under different polarizations when the grating period of the diffraction optical waveguide 100 of this embodiment is equal to 610nm. It can be seen that when the grating period of the diffraction optical waveguide 100 is equal to 610nm, the incident light wavelength corresponding to the optical waveguide of this embodiment can cover the red light band.

[0136] Therefore, it can be understood that the technical solution of the present invention can adjust the wavelength band of the incident light adapted to the asymmetric diffraction optical waveguide 100 by adjusting the grating period.

[0137] See also Figure 3 , Figure 3 The figure shows a partial structural diagram of the second embodiment of the diffractive optical waveguide 100 provided by the present invention, wherein the surface profile of the second grating periodic structure 22 of the asymmetric grating periodic unit 20 of the diffractive optical waveguide 100 gradually becomes nonlinear, thereby facilitating further increasing the asymmetry of the asymmetric grating periodic unit 20. In addition, this structural setting is more in line with the effect of directly coating the second grating periodic structure 22 in the film forming process, which can reduce the difficulty of preparing the asymmetric grating.

[0138] See also Figure 4 , Figure 4 FIG. 1 is a partial structural diagram of a third embodiment of a diffractive optical waveguide 100 provided by the present invention.

[0139] In an embodiment of the present invention, the asymmetric grating periodic unit 20 may include two second grating periodic structures 22, wherein the two second main body portions 222 of the two second grating periodic structures 22 are overlapped on the top of the first grating periodic structure 21, and the two first main body portions 221 are respectively arranged on the left and right sides of the first grating periodic structure 21.

[0140] Of course, in some embodiments, the number of the second grating periodic structures 22 may also be more than two, wherein the second main bodies 222 of several second grating periodic structures 22 are overlapped on the top of the first grating periodic structure 21, and the first main bodies 221 of several second grating periodic structures 22 may be alternately distributed on the left and right sides of the first grating periodic structure 21, or may be distributed on both sides of the first grating periodic structure 21 in other distribution modes, which is not limited here.

[0141] See also Figure 5 , Figure 5 FIG. 1 is a partial structural diagram of a fourth embodiment of a diffractive optical waveguide 100 provided by the present invention.

[0142] In an embodiment of the present invention, the asymmetric grating periodic unit 20 may include three second grating periodic structures 22, and the three first main bodies 221 of the three second grating periodic structures 22 are all located on the first side of the first grating periodic structure 21. In this way, the preparation of an asymmetric diffraction grating can also be achieved, and the asymmetric grating periodic unit 20 as a whole can be more inclined toward the first side of its first grating periodic structure 21.

[0143] It should be noted that in the related art, the optical efficiency of the diffraction optical waveguide 100 can be ensured by specifically designing a surface relief asymmetric grating with a special structure, such as a tilted grating. However, such a grating with a special structure has the problems of great difficulty in processing and high cost.

[0144] To this end, the present invention also proposes a method for preparing a diffractive optical waveguide 100, which aims to reduce the preparation difficulty and production cost of the diffractive optical waveguide 100 while ensuring the optical efficiency of the diffractive optical waveguide 100. The specific structure of the diffractive optical waveguide 100 refers to the above embodiment, and the preparation method specifically includes the following steps:

[0145] Coating nanoimprint glue on the imprint mask and / or the substrate 10 of the diffractive optical waveguide 100 to make the imprint mask and the substrate 10 fit together;

[0146] The nanoimprint glue is cured to prepare a first grating periodic structure 21 of at least one asymmetric grating periodic unit 20 on a surface of one side of the substrate 10;

[0147] The first grating periodic structure 21 is subjected to an oblique coating process, so as to obtain a second grating periodic structure 22 by coating the surface of the first grating periodic structure 21 .

[0148] The asymmetric grating of the diffraction optical waveguide 100 of the present invention includes at least one asymmetric grating periodic unit 20. The cross-sectional shape of the first grating periodic structure 21 in the asymmetric grating periodic unit 20 is a conventional symmetrical structure such as a rectangular or sinusoidal shape, and the preparation difficulty is relatively low. The first grating periodic structure 21 can be prepared on one side surface of the substrate 10 by a nanoimprint process.

[0149] Specifically, the substrate 10 can be set as a glass wafer, and the nanoimprint glue is spin-coated on the imprint mask or the glass wafer, and the imprint mask and the glass wafer are bonded to shape the applied nanoimprint glue. Of course, it is also possible to spin-coat a portion of the nanoimprint glue on the imprint mask and the glass wafer respectively, which is not limited here. The nanoimprint glue can be set as a heat-curing glue, and the first grating periodic structure 21 can be obtained by curing it on one side of the glass wafer by heating and curing it, or the nanoimprint glue can also be set as an ultraviolet curing glue, which can be cured by receiving ultraviolet light and formed on one side of the glass wafer.

[0150] Furthermore, an inclined coating process can be used to deposit inorganic materials, organic materials, or metal materials, so as to obtain a second grating periodic structure 22 by coating the surface of the first grating periodic structure 21, thereby completing the preparation of the diffraction optical waveguide 100. Among them, a single-layer second grating periodic structure 22 can be prepared on the first grating periodic structure 21 by the inclined coating process to obtain Figures 1 to 3 The diffractive optical waveguide 100 of the first embodiment and the second embodiment shown in the figure can also be prepared on the first grating periodic structure 21 by an inclined coating process to obtain a composite stacked structure formed by stacking a plurality of second grating periodic structures 22, so as to obtain Figures 4 to 5 The diffractive optical waveguide 100 of the third embodiment and the fourth embodiment shown are not limited here.

[0151] It can be understood that the preparation method of the present invention can achieve the preparation of asymmetric gratings by further tilting the coating on the conventional symmetric gratings prepared by the nanoimprinting process. The preparation method is simple and convenient, which is conducive to achieving high optical efficiency of the diffraction optical waveguide 100 while reducing the preparation difficulty and production cost of the diffraction optical waveguide 100, thereby facilitating mass production.

[0152] Further, in an embodiment of the present invention, the aforementioned step of “performing an oblique coating process on the first grating periodic structure 21 to obtain a second grating periodic structure 22 by coating the surface of the first grating periodic structure 21” further includes:

[0153] The substrate 10 is placed in a film forming area of ​​a film forming machine, so that the surface of the substrate 10 and the first grating periodic structure 21 are relatively inclined to the deposition direction of the target source of the film forming machine;

[0154] The second grating periodic structure 22 is deposited on the top and one side of the first grating periodic structure 21 .

[0155] Among them, the substrate 10 and the first grating periodic structure 21 thereon may be kept in a horizontal position in the film forming machine, and the target source may be tilted at a certain angle so that the substrate 10 and the first grating periodic structure 21 thereon are relatively tilted to the deposition direction of the target source of the film forming machine; or the substrate 10 and the first grating periodic structure 21 thereon may be tilted at a certain angle in the film forming machine, and the target source may be kept in a horizontal position so that the substrate 10 and the first grating periodic structure 21 thereon are relatively tilted to the deposition direction of the target source of the film forming machine, which is not limited here.

[0156] It can be understood that when the substrate 10 and the first grating periodic structure 21 are relatively tilted to the target source of the film-forming machine, due to the directional nature of the film-forming process and the shielding effect of the undulating shape of the first grating periodic structure 21 of the asymmetric grating periodic unit 20, when coating the surface of the first grating periodic structure 21, the deposited material will not fall evenly on the surface of the first grating periodic structure 21, but will tend to be deposited toward a single side of the first grating periodic structure 21, so that the second grating periodic structure 22 can be deposited on the top and one side of the first grating periodic structure 21 to achieve the preparation of an asymmetric grating.

[0157] Furthermore, in an embodiment of the present invention, before the aforementioned step of “coating nanoimprint glue on the imprint mask and / or the substrate 10 of the diffractive optical waveguide 100”, the following steps are further included:

[0158] The substrate 10 and the imprint mask are cleaned and hydrophobized respectively.

[0159] In this way, hydrophobic regions can be formed on the substrate 10 and the imprint mask respectively to achieve a better anti-sticking effect.

[0160] The present invention further proposes a display device, which includes a diffraction optical waveguide 100. The specific structure of the diffraction optical waveguide 100 refers to the above embodiment. Since the display device adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought by the technical solutions of the above embodiments, which will not be described one by one here.

[0161] The display device may be configured as an augmented reality display device, such as augmented reality glasses. The display device may emit a display image through a display device, and realize projection of the display image through the diffractive optical waveguide 100, so as to project the virtual image and the real world image into the user's eyes at the same time, thereby enabling the user to see the virtual image superimposed on the real scene.

[0162] The above are only exemplary embodiments of the present invention, and are not intended to limit the patent scope of the present invention. All equivalent structural changes made using the contents of the present invention's specification and drawings, or directly / indirectly applied in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A diffractive optical waveguide, characterized in that: The invention comprises a substrate and an asymmetric grating arranged on the substrate, wherein the asymmetric grating comprises at least one asymmetric grating periodic unit; each of the asymmetric grating periodic units comprises a first grating periodic structure whose cross-sectional shape is symmetrical about the grating axis plane, and also comprises a second grating periodic structure stacked on the first grating periodic structure, wherein the second grating periodic structure comprises: A first main body portion, the first main body portion is disposed on a first side surface of the first grating periodic structure; a second main body portion, the second main body portion being disposed on a top surface of the first grating periodic structure; and a third main body portion, the third main body portion being transitionally connected between the second main body portion and the first main body portion; A surface of the first main body portion on one side away from the first grating periodic structure is a first inclined surface. The first inclined surface extends in a direction away from the substrate and is inclined in a direction away from the first grating periodic structure.

2. The diffractive optical waveguide according to claim 1, characterized in that: The first inclined surface is arranged in a curved surface or a flat surface; And / or, the angle between the first inclined surface and the surface of the substrate is in the range of 60° to 90°; And / or, a minimum width of the first main body in an arrangement direction of the first main body and the first grating periodic structure ranges from 10 nm to 100 nm.

3. The diffractive optical waveguide according to claim 1, characterized in that: A surface of the second main body portion on one side away from the third main body portion is a second inclined surface. The second inclined surface extends in a direction away from the first grating periodic structure and is inclined toward the third main body portion.

4. The diffractive optical waveguide according to claim 3, characterized in that: The second inclined surface is arranged in a curved surface or a flat surface; And / or, the angle between the second inclined surface and the top surface of the first grating periodic structure is in the range of 40° to 90°; And / or, the top surface of the second main body is arranged parallel to the top surface of the first grating periodic structure, and the vertical distance from the top surface of the second main body to the top surface of the first grating periodic structure is defined as the thickness dc of the second main body, and the vertical distance from the top surface of the first grating periodic structure to the substrate surface is defined as the thickness dg of the first grating periodic structure, wherein dc=dg.

5. The diffractive optical waveguide according to any one of claims 1 to 4, characterized in that: The width of the top surface of the second grating periodic structure is greater than the width of the first grating periodic structure.

6. The diffractive optical waveguide according to any one of claims 1 to 4, characterized in that: The difference in refractive index between the second grating periodic structure and the first grating periodic structure is greater than 0.

2.

7. The diffractive optical waveguide according to any one of claims 1 to 4, characterized in that: The refractive index of the substrate ranges from 1.6 to 2.1; And / or, the grating period of the first grating periodic structure ranges from 350nm to 700nm; And / or, the duty cycle of the first grating periodic structure is in the range of 0.2 to 0.7; And / or, the refractive index of the first grating periodic structure is in the range of 1.6 to 2.1; And / or, a vertical distance from a top surface of the second main body to a top surface of the first grating periodic structure is a thickness dc of the second main body, and the thickness dc of the second main body is in a range of 40 nm to 300 nm; And / or, a vertical distance from the top surface of the first grating periodic structure to the surface of the substrate is a thickness dg of the first grating periodic structure, and the thickness dg of the first grating periodic structure is in a range of 50 nm to 300 nm; And / or, the refractive index of the second grating periodic structure is in the range of 1.9 to 3.

5.

8. The diffractive optical waveguide according to any one of claims 1 to 4, characterized in that: The asymmetric grating periodic unit also includes a third grating periodic structure, wherein one end of the third grating periodic structure facing the substrate is arranged on the second side surface of the first grating periodic structure, and the other end of the third grating periodic structure extends toward the top surface of the second grating periodic structure and is stacked on the top surface of the second grating periodic structure, and the third grating periodic structure and the second grating periodic structure have different refractive indices.

9. The diffractive optical waveguide according to claim 8, characterized in that: The difference in refractive index between the second grating periodic structure and the third grating periodic structure is greater than 0.1; And / or, a difference in refractive index between one of the second grating periodic structure and the third grating periodic structure and the first grating periodic structure is greater than 0.

2.

10. The diffractive optical waveguide according to claim 8, characterized in that: One end of the second grating periodic structure facing the substrate is connected to the substrate surface, and one end of the third grating periodic structure facing the substrate is connected to the substrate surface.

11. A diffractive optical waveguide as claimed in any one of claims 1 to 4, characterized in that The asymmetric grating periodic unit further comprises a multi-level grating periodic structure, and the multi-level grating periodic structure is stacked on the second grating periodic structure; Wherein, one end of the first-stage grating periodic structure in the multi-stage grating periodic structure is arranged on the first inclined surface, and the other end extends toward the top surface of the second grating periodic structure and is overlapped on the top surface of the second grating periodic structure; One end of the next grating periodic structure in the multi-level grating periodic structure is arranged on a side surface of the previous grating periodic structure away from the first main body, and the other end extends toward the top surface of the previous grating periodic structure and is overlapped on the top surface of the previous grating periodic structure.

12. The diffractive optical waveguide according to claim 11, wherein: One end of the second grating periodic structure facing the substrate is connected to the substrate surface; Each grating periodic structure in the multi-stage grating periodic structure is spaced apart from the substrate surface at one end facing the substrate, and the spacing between the subsequent grating periodic structure and the substrate surface is greater than the spacing between the previous grating periodic structure and the substrate surface.

13. The diffractive optical waveguide according to claim 12, wherein: Each level of the grating periodic structure in the multi-level grating periodic structure has a first surface and a second surface that are arranged opposite to each other in a direction from the first main body to the first grating periodic structure; The included angle between each of the first surfaces and the base surface is equal to the included angle between the first inclined surface and the base surface; And / or, a side surface of the second main body portion facing away from the third main body portion is defined as a second inclined surface, and an angle between each of the second surfaces and the base surface is equal to an angle between the second inclined surface and the base surface.

14. The diffractive optical waveguide according to claim 11, wherein: The difference in refractive index between the second grating periodic structure or at least one of the multi-stage grating periodic structure and the first grating periodic structure is greater than 0.2; And / or, the difference in refractive index between the first-level grating periodic structure and the second-level grating periodic structure is greater than 0.1, and the difference in refractive index between two adjacent levels of grating periodic structures in the multi-level grating periodic structure is greater than 0.

1.

15. A method for preparing a diffractive optical waveguide as claimed in any one of claims 1 to 14, characterized in that: The steps of the preparation method include: Coating nanoimprint glue on the imprint mask and / or the substrate of the diffractive optical waveguide to make the imprint mask and the substrate fit together; Curing the nanoimprint glue to prepare a first grating periodic structure of at least one asymmetric grating periodic unit on a surface of one side of the substrate; The first grating periodic structure is subjected to an inclined coating process to obtain a second grating periodic structure by coating the surface of the first grating periodic structure.

16. A display device, characterized in that: Comprising a diffractive optical waveguide as claimed in any one of claims 1 to 14.

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