Method for reducing optical loss in AR light guide plates

Abstract

A method for modifying an interface of an optical substrate. To achieve desired optical properties, surface defects must be removed from the interface layer. In one example, the substrate is exposed to an ion beam, followed by 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 can be added during high-temperature baking or laser annealing, and finally a protective layer can be added. If not removed, surface defects in the interface layer can absorb a percentage of light in a single interaction. In a waveguide, light can bounce tens to hundreds of times within the substrate, causing significant light loss. Therefore, removing surface defects significantly increases waveguide efficiency.

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE Embodiments of the present disclosure relate generally to optical devices. More particularly, embodiments described herein relate to methods for modifying a waveguide or optical device substrate interface. [Background technology]

[0002] Virtual reality is generally considered to be a computer-generated simulated environment in which a user has an apparent physical presence. Virtual reality experiences are generated in 3D and may be viewed using a head-mounted display (HMD), such as glasses or other wearable display devices, that have near-eye display panels as lenses for displaying the virtual reality environment that replaces the real environment.

[0003] Augmented reality (AR), however, enables an experience in which a user can still look through the display lenses of glasses or other HMD devices to view the surrounding environment, and also see images of virtual objects that are generated for display and appear as part of the environment. Augmented reality can include any type of input, such as audio and haptic input, as well as virtual images, graphics, and video, that enhances or augments the environment the user experiences.

[0004] One such challenge is displaying a virtual image overlaid on a surrounding environment. Waveguides, such as augmented reality waveguides, are used to assist in overlaying the image. Generated light is propagated through an optical device until the light exits the waveguide and is overlaid on the surrounding environment. It is desirable to improve the waveguide to reduce optical losses in the waveguide or in the optical device substrate of the waveguide. Therefore, what is needed in the art is a method for modifying the waveguide or optical device substrate interface. Summary of the Invention

[0005] In one embodiment, a method for fabricating a waveguide is provided. The method includes exposing a first interface layer of an optical device substrate to an ion beam. The optical device substrate includes a silicon carbide (SiC)-containing material, a lithium niobate (LiNbO)-containing material, a diamond (C)-containing material, a metal oxide-containing material, or a combination thereof, and the first interface layer is disposed on a first surface of the optical device substrate. The method further includes subjecting the optical device substrate to a firing or annealing process. The firing or annealing process recrystallizes the first interface layer, removes impurities from the first interface layer, or forms a second interface layer on the first surface of the optical device substrate.

[0006] In another embodiment, a method for fabricating a waveguide is provided. The method includes removing a first interface layer of an optical device substrate. The optical device substrate includes a silicon carbide (SiC)-containing material, a lithium niobate (LiNbO)-containing material, a diamond (C)-containing material, a metal oxide-containing material, or a combination thereof, and the first interface layer is disposed on a first surface of the optical device substrate. The method further includes forming a second interface layer using a firing 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 device substrate having a substrate material and an interface layer. The substrate material includes a silicon carbide (SiC)-containing material, a lithium niobate (LiNbO)-containing material, a diamond (C)-containing material, a metal oxide-containing material, or a combination thereof. The interface layer is disposed on the optical device substrate and includes the substrate material and a dopant material. The waveguide further includes at least one grating having an optical device structure disposed on the interface layer.

[0008] So that the above-recited features of the present disclosure may be understood in detail, a more particular description of the present disclosure briefly summarized above may be made by reference to embodiments, some of which are illustrated in the accompanying drawings. It should be noted, however, that the accompanying drawings illustrate only exemplary embodiments and therefore should not be considered limiting of its scope, as other equally effective embodiments may be recognized. [Brief explanation of the drawings]

[0009] [Figure 1A] FIG. 2 is a schematic top view of a waveguide combiner, according to an embodiment. [Figure 1B] 1 is a schematic cross-sectional view of a grating of a waveguide combiner, according to an embodiment. [Figure 2] 1 is a flow diagram of a method for modifying an interface of a substrate, according to an embodiment. [Figures 3A-3D] 1A-1C are schematic cross-sectional views of a substrate during a method of modifying an interface of the substrate, according to an embodiment. [Figure 4] 1 is a flow diagram of a method for modifying an interface of a substrate, according to an embodiment. [Figures 5A-5D] 1A-1C are schematic cross-sectional views of a substrate during a method of modifying an interface of the substrate, according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] For ease of understanding, like reference numerals have been used, where possible, to designate like elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.

[0011] The present disclosure generally relates to waveguides for augmented, virtual, and mixed reality. More particularly, embodiments described herein provide a method for modifying an interface of an optical substrate. In one embodiment, the substrate is exposed to an ion beam and then subjected to high-temperature baking 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 during a high-temperature baking or laser annealing process. A protective layer is deposited thereon.

[0012] 1A is a schematic top view of an optical device 100. The optical device 100 described below should be understood as an exemplary optical device. In one embodiment that can be combined with other embodiments described herein, the optical device 100 is a waveguide combiner, such as an augmented reality waveguide combiner. The optical device 100 includes a plurality of optical device structures 102 disposed on a surface 103 of a substrate 101. The optical device structures 102 can be nanostructures having submicron dimensions, e.g., nano-sized dimensions. In one embodiment that can be combined with other embodiments described herein, regions of the optical device 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, which may be combined with other embodiments described herein, the optical device 100 is a waveguide combiner including at least a first grating 104a corresponding to an input coupling grating and a third grating 104c corresponding to an output coupling grating. A waveguide combiner according to an embodiment, which may be combined with other embodiments described herein, includes a second grating 104b corresponding to an intermediate grating.

[0013] Substrate 101 may include, but is not limited to, silicon carbide (SiC)-containing materials, lithium niobate (LiNbO3)-containing materials, diamond (C)-containing materials, metal oxide-containing materials, or combinations thereof.

[0014] FIG. 1B is a schematic cross-sectional view of multiple optical device structures 102. FIG. 1B is taken along section line 1B-1B of optical device 100. In some embodiments, optical device 100 includes multiple optical device structures 102 disposed on a surface 103 of substrate 101. The optical device structures 102 may correspond to one or more gratings 104. In some embodiments, the multiple optical device structures 102 may include a first optical device structure 102A disposed across a first portion 103A of surface 103 and a second optical device structure 102B disposed across a second portion 103B of surface 103. Although FIG. 1B depicts optical device structures 102 as having a square or rectangular shaped cross-section, the cross-section of optical device structures 102 may have other shapes, including, but not limited to, a circular, triangular, elliptical, regular polygonal, irregular polygonal, and / or irregular shaped cross-section. In some embodiments, which may be combined with other embodiments described herein, the cross sections of the optical device structures 102 have cross sections with different shapes. In other embodiments, which may be combined with other embodiments described herein, the cross sections of the optical device structures 102 have cross sections with substantially the same shape.

[0015] In some embodiments, the first optical device structure 102A can be substantially vertical (in other words, binary). The sidewalls 118 of the first optical device are parallel to each other and perpendicular to the surface 103 of the substrate 101. The first optical device structure 102A is formed from the substrate 101.

[0016] The second optical device structures 102B are angled at 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 device structures 102B. In one embodiment, which may be combined with other embodiments described herein, the device angle θ of each respective second optical device structure 102B is substantially equal across the substrate 101. In another embodiment, which may be combined with other embodiments described herein, the device angle θ of at least one respective second optical device structure 102B is different from the device angle θ of another of the plurality of second optical device structures 102B. The second optical device structures 102B are formed similarly to the first optical device structures.

[0017] FIG. 2 is a flow chart of a method 200 for modifying a substrate interface according to an embodiment, as shown in FIGS. 3A-3D. FIGS. 3A-3D are schematic cross-sectional views of a substrate 101 during the method 200. Prior to step 201, as shown in FIG. 3A, the surface 103 of the substrate 101 has an interface layer 301 formed thereon. The first interface layer 301 has a thickness of 1 angstrom to 10 nm. In one embodiment, the substrate 101 has an optical device structure 102 forming a grating 104 disposed in the interface layer 301. The interface layer 301 has surface defects that can cause optical loss in the substrate 101. The surface defects can be introduced during fabrication. Surface defects include impurities, surface roughness, nanoscratches, or crystal dislocations. Crystal dislocations can be present when the substrate 101 is made of a crystalline material. Crystal dislocations can be caused by overhanging bonds that place atoms out of their predetermined positions in the crystal structure. These misplaced atoms can create additional energy levels that cause the substrate 101 to absorb more light and increase light loss. Nanoscratching can be present when the substrate 101 is made from the materials of the substrate 101 provided herein. The nanoscratches can be 1 Angstrom deep to 20 nm deep in the first interface layer 301.

[0018] In step 201, as shown in FIG. 3B, the substrate 101 is exposed to an ion beam 302. The ion beam 302 may include argon, nitrogen, or oxygen-containing chemicals. In one embodiment, as shown in FIG. 3B, the ion beam 302 may modify the crystalline structure of the interface layer 301 and the substrate 101 to a depth 311. The modified crystalline structure is then ready to be reconstructed. In another embodiment, as shown in FIG. 3C, the ion beam 302 may deposit a dopant material into the interface layer 301 and into the substrate 101 to a depth 311. The dopant material may include at least one of boron, aluminum, gallium, oxygen, nitrogen, or phosphorus-containing materials. The dopant may remove an absorbing bond connecting the interface layer 301 and the substrate 101. The dopant breaks the overhanging bond between atoms in the overhanging bond. The atom then bonds to other atoms to form new bonds. The new bond has a higher energy level, e.g., a covalent bond, that is high enough that visible light cannot interact with the higher energy bond, reducing light absorption.

[0019] In step 202, substrate 101 is subjected to a firing or annealing process. The annealing or firing process either recrystallizes interface layer 301, removes impurities from interface layer 301, or forms a second interface layer (not shown) on surface 103, as shown in FIG. 3D. In one embodiment, the firing process is a high temperature firing. In another embodiment, the annealing process can be a laser annealing process. The second interface layer can have the same composition as substrate 101.

[0020] FIG. 4 is a flow chart of a method 400 for modifying a substrate interface according to an embodiment, as shown in FIGS. 5A-5D. FIGS. 5A-5D are schematic cross-sectional views of a substrate 101 during method 400. Prior to step 401, as shown in FIG. 5A, the surface 103 of the substrate 101 has an interface layer 301 formed thereon. The first interface layer 301 has a thickness of 1 angstrom to 10 nanometers (nm). In one embodiment, the substrate 101 has an optical device structure 102 disposed on the surface 103. The interface layer 301 has surface defects that can cause optical loss in the substrate 101. The surface defects can be introduced during fabrication. The surface defects include impurities, surface roughness, or crystal dislocations. In step 401, the interface layer 301 is removed. The interface layer 301 can be removed by an etching process 502, as shown in FIG. 5B. In one embodiment, wet chemical etching is used. The wet chemical etch may include dilute hydrofluoric acid (DHF). In another embodiment, an ion beam is used. The ion beam may be a high-energy ion beam.

[0021] In step 402, a second interface layer 501 is formed. In one embodiment, the second interface layer 501 is regrown using an annealing process, as shown in FIG. 5C. The second interface layer 501 has a thickness of 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.

[0022] In step 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), titanium oxide (TiO), or silicon nitride (SiN). The protective layer 505 has a thickness of 1 angstrom to 10 nm, such as 1 angstrom to 5 nm.

[0023] In summary, this is a method for modifying the interface of an optical substrate. To achieve desired optical properties, surface defects need to be removed from the interface layer 301. In one example, the substrate is exposed to an ion beam, followed by 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 can be added during high-temperature baking or laser annealing, and finally, a protective layer can be added. If not removed, surface defects in the interface layer 301 can absorb a percentage of light in a single interaction. In a waveguide, light can bounce tens to hundreds of times within the substrate, causing significant light loss through absorption. Therefore, removing surface defects significantly increases waveguide efficiency.

[0024] While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the present disclosure may be devised without departing from the basic scope thereof, the scope of which is determined by the claims that follow.

Claims

1. exposing a first interface layer of an optical device substrate to an ion beam, the optical device substrate being made of a material selected from the group consisting of silicon carbide (SiC)-containing materials, lithium niobate (LiNbO ３ exposing a first interface layer of an optical device substrate to an ion beam, the first interface layer comprising a diamond(C)-containing material, a diamond(C)-containing material, a metal oxide-containing material, or a combination thereof, the first interface layer being disposed on a first surface of the optical device substrate; subjecting the optical device substrate to a firing or annealing process, wherein the firing or annealing process recrystallizes the first interface layer, removes impurities from the first interface layer, or forms a second interface layer on the first surface of the optical device substrate; A method for manufacturing a waveguide, comprising:

2. The method of claim 1 , wherein the ion beam comprises an argon, nitrogen, or oxygen-containing chemical.

3. The method of claim 1 , wherein the firing process is a high temperature firing.

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

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

6. 6. The method of claim 5, wherein the optical device structures have sidewalls that are parallel to one another and angled relative to the first surface of the optical device substrate, and the optical device structures are disposed on the first interface layer.

7. The method of claim 1 , wherein exposing the first interface layer to the ion beam deposits dopants in the first interface layer to remove absorbing coupling.

8. The method of claim 1 , wherein exposing the first interface layer to the ion beam modifies the crystal structure of the first interface layer prior to the firing process or the annealing process.

9. removing a first interface layer of an optical device substrate, the optical device substrate being made of a material selected from the group consisting of silicon carbide (SiC)-containing materials, lithium niobate (LiNbO ３ removing a first interface layer of an optical device substrate, the first interface layer comprising a diamond(C)-containing material, a diamond(C)-containing material, a metal oxide-containing material, or a combination thereof, the first interface layer being disposed on a first surface of the optical device substrate; forming a second interface layer using a firing or annealing process; depositing a protective layer on the second interface layer; A method for manufacturing a waveguide, comprising:

10. The method of claim 9 , wherein the first interface layer is removed by a wet etching process.

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

12. The protective layer is made of silicon oxide (SiO ２ ) or silicon nitride (Si ３ N ４ 10. The method of claim 9, comprising:

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

14. 14. The method of claim 13, wherein the optical device structures have sidewalls that are parallel to one another and perpendicular to the first surface of the optical device substrate, and the optical device structures are disposed on the first interface layer.

15. The method of claim 9, wherein the firing process is a high temperature firing.

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

17. An optical device substrate having a substrate material, the substrate material being selected from the group consisting of silicon carbide (SiC)-containing materials, lithium niobate (LiNbO ３ an optical device substrate comprising a diamond(C)-containing material, a diamond(C)-containing material, a metal oxide-containing material, or a combination thereof; an interface layer disposed on the optical device substrate, the interface layer comprising the substrate material and a dopant material; at least one grating having an optical device structure disposed in the interface layer; A waveguide comprising:

18. 20. The waveguide of claim 17, further comprising a protective layer disposed on the interface layer.

19. The protective layer is made of silicon oxide (SiO ２ ), titanium oxide (TiO ２ ), or silicon nitride (Si ３ N ４ 20. The waveguide of claim 18, comprising:

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

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