Method of reducing augmented reality (AR) waveguide optical loss

Abstract

A method of optical substrate interface modification is provided. In order to achieve ideal optical properties, surface defects in the interface layer must be removed. In one example, the substrate may be exposed to an ion beam and then subjected to high temperature baking or laser annealing to modify the interface layer. In another example, the interface layer can be removed using a high energy ion beam, then a new interface layer is added during high temperature baking or laser annealing, and finally a protective layer is added. If surface defects in the interface layer are not removed, a portion of the light may be absorbed in a single interaction. In a waveguide, light may rebound ten to hundreds of times within a substrate, resulting in significant light loss. Therefore, the efficiency of the waveguide is remarkably improved by removing the surface defects.

Description

Technical Field

[0001] Embodiments of the present disclosure generally relate to optical elements. More specifically, the embodiments described in this document relate to methods for modifying waveguide or optical element substrate interfaces. Background Art

[0002] Virtual reality is generally considered to be a computer-generated simulation environment in which the user has an apparent physical presence. A virtual reality experience can be generated in 3D and viewed through a head-mounted display (HMD), such as glasses with near-eye display panels as lenses or other wearable display devices, to display a virtual reality environment that replaces the actual environment.

[0003] However, augmented reality (AR) allows users to see the surrounding environment through the display lenses of glasses or other HMD devices, while also being able to see images of virtual objects that are generated and displayed as part of the environment. Augmented reality can include any type of input, such as audio and tactile input, as well as virtual images, graphics, and videos that enhance or augment the user experience.

[0004] One challenge is how to display overlapping virtual images in the environment. Waveguides, such as augmented reality waveguides, are used to assist in overlapping images. The generated light propagates through the optical element until the light exits the waveguide and overlaps in the environment. It is desirable to be able to modify the waveguide to reduce optical losses in the waveguide or the optical element substrate of the waveguide. Therefore, there is a need in the industry for methods to modify waveguide or optical element substrate interfaces. Summary of the Invention

[0005] In one embodiment, a method of manufacturing a waveguide is provided. The method includes exposing a first interface layer of an optical element substrate to an ion beam. The optical element substrate includes a material containing silicon carbide (SiC), a material containing lithium niobate (LiNbO 3 ), a material containing diamond (C), a material containing metal oxide, or a combination thereof, and the first interface layer is located on the first surface of the optical element substrate. The method further includes performing a baking process or an annealing process on the optical element substrate. The baking process or the annealing process can recrystallize the first interface layer, remove impurities from the first interface layer, or form a second interface layer on the first surface of the optical element substrate.

[0006] In another embodiment, a method of manufacturing a waveguide is provided. The method includes removing a first interface layer of an optical element substrate. The optical element substrate includes a material containing silicon carbide (SiC), a material containing lithium niobate (LiNbO 3), a material containing diamond (C), a material containing a metal oxide, or a combination thereof, and the first interface layer is located on the first surface of the optical element substrate. The method further includes forming a second interface layer using a baking process or an annealing process, and depositing a protective layer on the second interface layer.

[0007] In another embodiment, a waveguide is provided. The waveguide includes an optical element substrate having a substrate material and an interface layer. The substrate material includes a material containing silicon carbide (SiC), a material containing lithium niobate (LiNbO 3 ), a material containing diamond (C), a material containing a metal oxide, or a combination thereof. The interface layer is located on the optical element substrate and includes the substrate material and a dopant material. The waveguide further includes at least one grating that disposes an optical element structure in the interface layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] To enable a more detailed understanding of the features disclosed above, reference may be made to the more specific descriptions of the disclosure briefly summarized above, which descriptions include some embodiments illustrated in the appended drawings. However, it should be noted that the appended drawings only show exemplary embodiments and should not be considered as limiting its scope, and there may be other equally effective embodiments.

[0009] Figure 1A is a schematic top view of a waveguide combiner according to an embodiment.

[0010] Figure 1B is a schematic cross-sectional view of a grating of a waveguide combiner according to an embodiment.

[0011] Figure 2 is a flowchart of a method for modifying a substrate interface according to an embodiment.

[0012] Figures 3A - 3D is a schematic cross-sectional view of a substrate during the method for modifying a substrate interface according to an embodiment.

[0013] Figure 4 is a flowchart of a method for modifying a substrate interface according to an embodiment.

[0014] Figures 5A - 5D is a schematic cross-sectional view of a substrate during the method for modifying a substrate interface according to an embodiment.

[0015] For ease of understanding, whenever possible, the same reference numerals are used to denote the same elements in the figures. It is contemplated that the elements and features of one embodiment may be beneficially incorporated into other embodiments without further recitation. DETAILED DESCRIPTION

[0016] The present disclosure generally relates to waveguides for augmented reality, virtual reality, and mixed reality. More specifically, the embodiments described herein provide methods for modifying an optical substrate interface. In one embodiment, the substrate is exposed to an ion beam and then subjected to a high-temperature bake or laser annealing to modify the interface layer. In another embodiment, the interface layer is removed using a high-energy ion beam and then a new interface layer is added in a high-temperature bake process or a laser annealing process. A protective layer is deposited thereon.

[0017] Figure 1A is a schematic top view of an optical element 100. The optical element 100 described below should be understood as an exemplary optical element. In one embodiment that can be combined with other embodiments in this document, the optical element 100 is a waveguide combiner, such as an augmented reality waveguide combiner. The optical element 100 includes a plurality of optical element structures 102 located on a surface 103 of a substrate 101. The optical element structures 102 may be nanostructures having sub-micron dimensions, such as nanoscale dimensions. In one embodiment that can be combined with other embodiments in this document, the regions of the optical element structures 102 correspond to one or more gratings 104, such as a first grating 104a, a second grating 104b, and a third grating 104c. In another embodiment that can be combined with other embodiments in this document, the optical element 100 is a waveguide combiner that includes at least a first grating 104a corresponding to an input coupling grating and a third grating 104c corresponding to an output coupling grating. According to this embodiment, the waveguide combiner can be combined with other embodiments in this document and includes a second grating 104b corresponding to an intermediate grating.

[0018] The substrate 101 includes, but is not limited to, materials containing silicon carbide (SiC), materials containing lithium niobate (LiNbO 3 ) materials, materials containing diamond (C), materials containing metal oxides, or combinations thereof.

[0019] Figure 1B is a schematic cross-sectional view of a plurality of optical element structures 102. Figure 1B Located on the cut line 1B-1B of the optical element 100. In certain embodiments, the optical element 100 includes a plurality of optical element structures 102 located on a surface 103 of a substrate 101. The optical element structures 102 may correspond to one or more gratings 104. In certain embodiments, the plurality of optical element structures 102 may include a first optical element structure 102A located on a first portion 103A of the surface 103 and a second optical element structure 102B located on a second portion 103B of the surface 103. Although Figure 1BThe cross-section of the display optical element structure 102 is square or rectangular, but the cross-section of the optical element structure 102 can have other shapes, including but not limited to circular, triangular, elliptical, regular polygon, irregular polygon, and / or irregular-shaped cross-sections. In some embodiments that can be combined with other embodiments described herein, the cross-sections of multiple optical element structures 102 have cross-sections of different shapes. In other embodiments that can also be combined with other embodiments described herein, the cross-sections of the optical element structure 102 have cross-sections of substantially the same shape.

[0020] In some embodiments, the first optical element structure 102A can be substantially vertical (i.e., binary). The sidewalls 118 of the first optical element are parallel to each other and perpendicular to the surface 103 of the substrate 101. The first optical element structure 102A is formed on the substrate 101.

[0021] The second optical element structure 102B presents a device angle ϑ with respect to the substrate 101. The device angle ϑ is the angle between the surface 103 of the substrate 101 and the sidewall 118 of the second optical element structure 102B. In one embodiment, which can be combined with other embodiments described herein, the respective device angles ϑ of each second optical element structure 102B are substantially equal throughout the substrate 101. In another embodiment, which can be combined with other embodiments described herein, the device angle ϑ of at least one second optical element structure 102B is different from the device angles ϑ of other second optical element structures 102B. The second optical element structure 102B is formed in the same manner as the first optical element structure.

[0022] Figure 2 is according to Figures 3A - 3D The flowchart of the process 200 for modifying the substrate interface in the illustrated embodiment. Figures 3A - 3D is a schematic cross-sectional view of the substrate 101 during the process 200. Before operation 201, as Figure 3AAs shown, an interface layer 301 is formed on the surface 103 of the substrate 101. The thickness range of the first interface layer 301 is from 1 angstrom to 10 nanometers. In one embodiment, the substrate 101 has an optical element structure 102 formed in the interface layer 301 to form a grating 104. Surface defects existing in the interface layer 301 may cause light loss in the substrate 101. These surface defects may be introduced during the manufacturing process. Surface defects include impurities, surface roughness, nano-scratches, or crystal dislocations. When the substrate 101 is made of crystalline material, crystal dislocations may exist. Crystal dislocations may be caused by dangling bonds that misplace the atoms in the crystal structure. These misplaced atoms may result in additional energy levels, causing the substrate 101 to absorb more light and increasing light loss. When the substrate 101 is made of the materials provided herein, nano-scratches may exist. The depth of the nano-scratches may be from 1 angstrom to 20 nm and is located in the first interface layer 301.

[0023] In operation 201, as Figure 3B shown, the substrate 101 is exposed to an ion beam 302. The ion beam 302 may include chemicals containing argon, nitrogen, or oxygen. In one embodiment, as Figure 3B shown, the ion beam 302 may modify the crystal structure of the interface layer 301 and the substrate 101 to a depth 311. The modified crystal structure is then ready for reconstruction. In another embodiment, as Figure 3C shown, the ion beam 302 may deposit a dopant material in the interface layer 301 and the substrate 101 to a depth 311. The dopant material includes at least one of the following: boron-containing, aluminum-containing, gallium-containing, oxygen-containing, nitrogen-containing, or phosphorus-containing materials. These dopants may remove the absorption bonds connecting the interface layer 301 and the substrate 101. The dopants break the dangling bonds between the atoms in the dangling bonds. Subsequently, these atoms form new bonds with other atoms. The energy levels of these new bonds are higher, such as covalent bonds. These higher energy levels are high enough so that visible light cannot interact with these high-energy bonds, thereby reducing light absorption.

[0024] In operation 202, the substrate 101 undergoes a baking or annealing process. The annealing process or the baking process either recrystallizes the interface layer 301, removes the impurities in the interface layer 301, or forms a second interface layer (not shown) on the surface 103, as Figure 3D shown. In one embodiment, the baking process is a high-temperature baking. In another embodiment, the annealing process may be a laser annealing process. The composition of the second interface layer may be the same as that of the substrate 101.

[0025] Figure 4 is a flowchart of a method 400 for modifying a substrate interface according to an embodiment Figures 5A - 5D shown. Figures 5A - 5Dis a schematic cross-sectional view of the substrate 101 in method 400. Before operation 401, as Figure 5A shown, an interface layer 301 is formed on the surface 103 of the substrate 101. The thickness of the first interface layer 301 is from 1 angstrom to 10 nanometers (nm). In one embodiment, an optical element structure 102 is disposed on the surface 103 of the substrate 101. The interface layer 301 has surface defects that may cause light loss in the substrate 101. These surface defects can be introduced during the manufacturing process. Surface defects include impurities, surface roughness, or crystal dislocations. In operation 401, the interface layer 301 is removed. The interface layer 301 can be removed by an etching process 502 as Figure 5B shown. In one embodiment, a wet etching chemical is used. This wet etching chemical can include diluted hydrofluoric acid (DHF). In another embodiment, an ion beam is used. The ion beam may be a high-energy ion beam.

[0026] In operation 402, a second interface layer 501 is formed. In one embodiment, the second interface layer 501 is regrown by an annealing process, as Figure 5C shown. The thickness of the second interface layer 501 is from 1 angstrom to 10 nm. In one embodiment, the second interface layer is formed by a baking process, such as high-temperature baking. In another embodiment, the annealing process can be a laser annealing process.

[0027] In operation 403, a protective layer 505 is deposited on the surface of the second interface layer 501. The protective layer 505 includes but is not limited to silicon oxide (SiO 2 ), titanium oxide (TiO 2 ), or silicon nitride (Si 3 N 4 ). The thickness of the protective layer 505 is from 1 angstrom to 10 nm, for example, from 1 angstrom to 5 nm.

[0028] In summary, a method for modifying the interface of an optical substrate is provided. To achieve ideal optical properties, it is necessary to remove surface defects from the interface layer 301. In one example, the substrate is exposed to an ion beam and then subjected to high-temperature baking or laser annealing to correct the interface layer. In another example, a high-energy ion beam can be used to remove the interface layer, and then a new interface layer is added during high-temperature baking or laser annealing, and finally a protective layer is added. If the surface defects in the interface layer 301 are not removed, a certain proportion of light may be absorbed in a single interaction. In a waveguide, light may bounce inside the substrate ten to hundreds of times, resulting in significant light loss due to transmission absorption. Therefore, removing surface defects significantly improves the efficiency of the waveguide.

[0029] While the foregoing is directed to embodiments of the present disclosure, other and further embodiments may be devised without departing from its basic scope, the scope thereof being determined by the claims that follow.

Claims

1. A method of manufacturing a waveguide, the method comprises: Expose a first interface layer of an optical element substrate, the optical element substrate comprising a material containing silicon carbide (SiC), a material containing lithium niobate (LiNbO 3 ), a material containing diamond (C), a material containing a metal oxide, or a combination thereof, and the first interface layer being located on a first surface of the optical element substrate; and performing a baking process or an annealing process on the optical element substrate, wherein the baking process or the annealing process can recrystallize the first interface layer, remove impurities of the first interface layer, or form a second interface layer on the first surface of the optical element substrate.

2. The method according to claim 1, wherein the ion beam contains a chemical substance containing argon, nitrogen or oxygen.

3. The method according to claim 1, wherein the baking process is a high-temperature baking.

4. The method according to claim 1, wherein the annealing process is a laser annealing process.

5. The method according to claim 1, wherein the first surface of the optical element substrate comprises a plurality of optical element structures.

6. The method according to claim 5, wherein side walls of the optical element structures are parallel to each other and are at an angle with respect to the first surface of the optical element substrate, and the optical element structures are located in the first interface layer.

7. The method according to claim 1, wherein the first interface layer is exposed to the ion beam to deposit a dopant in the first interface layer to remove absorption bonding.

8. The method according to claim 1, wherein the first interface layer is exposed to the ion beam to change the crystal structure of the first interface layer before the baking process or the annealing process.

9. A method of manufacturing a waveguide, the method comprises: Remove a first interface layer of an optical element substrate, the optical element substrate including a material containing silicon carbide (SiC), a material containing lithium niobate (LiNbO 3 ), a material containing diamond (C), a metal oxide material, or a combination thereof, the first interface layer being located on a first surface of the optical element substrate; forming a second interface layer using a baking process or an annealing process; and depositing a protective layer on the second interface layer.

10. The method according to claim 9, wherein the first interface layer is removed by wet etching.

11. The method according to claim 9, wherein the first interface layer is removed by an ion beam.

12. The method according to claim 9, wherein the protective layer comprises silicon dioxide (SiO 2 ), or silicon nitride (Si 3 N 4 ).

13. The method according to claim 9, wherein the first surface of the optical element substrate comprises a plurality of optical element structures.

14. The method according to claim 13, wherein side walls of the optical element structures are parallel to each other and are perpendicular to the first surface of the optical element substrate, and the optical element structures are disposed in the first interface layer.

15. The method according to claim 9, wherein the baking process is a high-temperature baking.

16. The method according to claim 9, wherein the annealing process is a laser annealing process.

17. A waveguide, the waveguide comprises: Optical element substrate, the optical element substrate having a substrate material, the substrate material comprising a material containing silicon carbide (SiC), a material containing lithium niobate (LiNbO 3 ) material, a material containing diamond (C), a metal oxide material, or a combination thereof; an interface layer, the interface layer is located on the optical element substrate, and the interface layer contains the substrate material and the dopant material; and at least one grating, the at least one grating has optical element structures disposed in the interface layer.

18. The waveguide according to claim 17, the waveguide further comprises a protective layer, and the protective layer is disposed on the interface layer.

19. The waveguide according to claim 18, wherein the protective layer comprises silicon oxide (SiO 2 ), titanium oxide (TiO 2 ), or silicon nitride (Si 3 N 4 ).

20. The waveguide according to claim 17, wherein the doping material comprises at least one of the following: boron-containing, aluminum-containing, gallium-containing, oxygen-containing, nitrogen-containing or phosphorus-containing materials.

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