Method of manufacturing a waveguide combiner

Abstract

Embodiments described herein relate to methods for fabricating waveguide combiners. The methods provide waveguide combiners having input coupling regions, waveguide regions, and output coupling regions defined fine gratings formed of inorganic or hybrid (organic and inorganic) materials. In one embodiment, a waveguide structure is formed from a stamping die having a positive waveguide pattern on a resist disposed on a surface of a substrate to form a negative waveguide structure. The inorganic or hybrid material is deposited on the substrate and then the resist is removed to form a waveguide structure having regions corresponding to at least one of the input coupling regions, waveguide regions, and output coupling regions formed of inorganic or hybrid (organic and inorganic) materials.

Description

[0001] This application is a divisional application of the invention patent application filed on November 13, 2018, with application number 201880081384.0 and entitled "Method for Manufacturing Waveguide Combiner". Technical Field

[0002] The embodiments of this disclosure generally relate to waveguides for augmented reality, virtual reality, and mixed reality. More specifically, the embodiments described herein provide methods for manufacturing waveguides. Background Technology

[0003] Virtual reality is generally considered to be a computer-generated simulated environment in which the user has a tangible physical presence. Virtual reality experiences can be generated in 3D and viewed using head-mounted displays (HMDs), such as glasses or other wearable display devices with near-eye display panels as lenses to display a virtual reality environment that substitutes for the actual environment.

[0004] However, augmented reality (AR) technology offers the experience that users can still see their surroundings through the display lenses of glasses or other HMD devices, and can also see images of virtual objects generated for display and appearing as part of the environment. AR can include any type of input, such as audio and haptic input, as well as virtual images, graphics, and videos that can enhance or augment the environment experienced by the user. As an emerging technology, AR faces many challenges and design constraints.

[0005] One such challenge is displaying a virtual image superimposed on the surrounding environment. Waveguides are used to assist in the image superposition. The generated light propagates through the waveguide until it leaves the waveguide and is superimposed on the surrounding environment. Because waveguides tend to have inhomogeneous properties, fabricating them can be challenging. Therefore, there is a need in the art for improved waveguide enhancement and fabrication methods. Summary of the Invention

[0006] In one embodiment, a method of manufacturing a waveguide structure is provided. The method includes imprinting a mold into a photoresist. The mold has a positive waveguide pattern including at least one patterned portion. The imprinting forms a negative waveguide structure including a negative region with a residual layer. The photoresist is disposed on a surface of a portion of a substrate, and the substrate has a first refractive index. The photoresist is cured onto the surface of the substrate. The mold is released and the residual layer is removed. A coating is deposited. The coating has a second refractive index that substantially matches or is greater than the first refractive index of the surface of the substrate. The photoresist is removed from the waveguide structure including the region.

[0007] In another embodiment, a method for manufacturing a waveguide structure is provided. The method includes depositing a coating having a second refractive index on a negative waveguide structure of an imprint. The second refractive index substantially matches or is greater than a first refractive index of a substrate. The negative waveguide structure includes an anti-reflection region. The coating is planarized and bonded to a surface of a portion of the substrate. The imprint is released to form the waveguide structure including the region.

[0008] In another embodiment, a method for manufacturing a waveguide structure is provided. The method includes depositing a coating having a second refractive index between 1.5 and 2.5 on a negative waveguide structure of an imprint. The coating is substantially planar on the negative waveguide structure. The second refractive index substantially matches or is greater than a first refractive index between 1.5 and 2.5 of the substrate. The negative waveguide structure includes an anti-input coupling region and an anti-output coupling region. The coating is bonded to a surface of a portion of the substrate. An optical adhesive having a third refractive index substantially matching the first and second refractive indices is disposed on the surface of the substrate. The imprint is released to form a waveguide structure having regions. Attached Figure Description

[0009] To gain a more detailed understanding of the features described above in this disclosure, reference can be made to embodiments to provide a more specific description of the disclosure briefly outlined above, some of which are illustrated in the accompanying drawings. However, it should be noted that the drawings illustrate exemplary embodiments only and should not be construed as limiting the scope of this disclosure, allowing for other equivalent embodiments.

[0010] Figure 1 This is a perspective front view of a waveguide combiner according to one embodiment.

[0011] Figure 2 This is a flowchart illustrating the operation of a method for manufacturing a waveguide structure according to one embodiment.

[0012] Figures 3A to 3F This is a schematic cross-sectional view of a waveguide structure during a method for manufacturing a waveguide structure, according to one embodiment.

[0013] Figure 4 This is a flowchart illustrating the operation of a method for manufacturing a waveguide structure according to one embodiment.

[0014] Figures 5A to 5D This is a schematic cross-sectional view of a waveguide structure during a method for manufacturing a waveguide structure, according to one embodiment.

[0015] For ease of understanding, the same reference numerals have been used as much as possible to indicate common elements in the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated into other embodiments without further description. Detailed Implementation

[0016] The embodiments described herein relate to methods for manufacturing waveguide structures. The methods described herein enable the fabrication of waveguide structures having an input coupling region, a waveguide region, and an output coupling region formed of inorganic or hybrid (organic and inorganic) materials.

[0017] Figure 1 This is a perspective front view of waveguide combiner 100. It should be understood that the waveguide combiner 100 described below is an exemplary waveguide combiner. Waveguide combiner 100 includes an input coupling region 102 defined by a plurality of gratings 108, a waveguide region 104, and an output coupling region 106 defined by a plurality of gratings 110.

[0018] The input coupling region 102 receives an incident beam (virtual image) of a certain intensity from a microdisplay. Each of the plurality of gratings 108 divides the incident beam into multiple modes, each beam having one mode. The zero-order mode (TO) beam is refracted back or lost in the waveguide combiner 100, the positive first-order mode (T1) beam undergoes total internal reflection (TIR) ​​through the waveguide combiner 100, passes through the waveguide region 104, and reaches the output coupling region 106, while the negative first-order mode (T-1) beam propagates in the waveguide combiner 100 in the opposite direction to the T1 beam. The T1 beam undergoes total internal reflection (TIR) ​​through the waveguide combiner 100 until it contacts the plurality of gratings 110 in the output coupling region 106. The T1 beam contacts a grating in one of the plurality of gratings 110, wherein the T1 beam is divided into a T0 beam, a T1 beam and a T-1 beam, the T0 beam is refracted back or lost in the beam combiner 100, the T1 beam undergoes TIR in the output coupling region 106 until the T1 beam contacts another grating in the plurality of gratings 110, and the T-1 beam couples out of the waveguide combiner 100.

[0019] Figure 2 This is an example used in manufacturing such as Figures 3A to 3FA flowchart illustrating the operation of method 200 with waveguide structure 300 is provided. In one embodiment, waveguide structure 300 corresponds to at least one of the input coupling region 102, waveguide region 104, and output coupling region 106 of waveguide combiner 100. In another embodiment, waveguide structure 300 corresponds to a mother plate of at least one of the input coupling region 102, waveguide region 104, and output coupling region 106 of waveguide combiner 100. At operation 201, a mold 308 having a positive waveguide pattern 310 is imprinted onto a resist 326 disposed on a surface 306 of a portion 302 of substrate 304 to form a negative waveguide structure 312. Substrate 304 has a first refractive index. In one embodiment, substrate 304 comprises at least one of glass and plastic materials.

[0020] like Figure 3A As shown, the positive waveguide pattern 310 includes at least one patterned portion 314 to form at least one of the input coupling region 102, waveguide region 104, and output coupling region 106 of the waveguide combiner 100. Figure 3A and Figure 3B As shown, the negative waveguide structure 312 includes an inverse region 316 having a residual layer 318, commonly referred to as the bottom surface. In one embodiment, the inverse region 316 includes a plurality of reflective gratings 320 to form at least one of a plurality of gratings 108 of the input coupling region 102, a plurality of gratings 110 of the output coupling region 106, and the waveguide region 104. In one embodiment, the reflective grating 320 has an inverse top surface 322 parallel to the surface 306 of the substrate 304, an inverse sidewall surface 324, and a residual layer 318 parallel to the surface 306 of the substrate 304. In one embodiment, each of the inverse sidewall surfaces 324 of the reflective grating 320 is oriented perpendicular to the surface 306 of the substrate 304. In another embodiment, each of the inverse sidewall surfaces 324 of the reflective grating 320 is angled relative to the surface 306 of the substrate 304. In yet another embodiment, a portion of the reverse sidewall surface 324 is vertically oriented, and a portion of the reverse sidewall surface 324 of the reflector 320 is angled relative to the surface 306 of the substrate 304.

[0021] At operation 202, the resist 326 on surface 306 of substrate 304 is cured to stabilize the resist 326. At operation 203, the mold 308 is released from the resist 326. In one embodiment, the mold 308 is made of a waveguide mother plate having a negative pattern, the negative pattern including inverted pattern portions. The mold 308 is molded from the waveguide mother plate. The mold 308 includes a translucent material, such as fused silica or polydimethylsiloxane (PDMS), to allow the resist 326 to cure by exposure to electromagnetic radiation, such as infrared (IR) radiation or ultraviolet (UV) radiation. In one embodiment, the resist 326 includes a UV-curable material (such as mr-N210 available from Micro Resist Technology), which can be nanoimprinted by the mold 308 including PDMS. In one embodiment, the surface 306 of the substrate 304 is prepared by UV ozone treatment, oxygen (O2) plasma treatment, or by spin-coating a UV-curable material using a primer (such as mr-APS1, available from Micro Resist Technology). The resist 326 may alternatively be thermally cured. In another embodiment, the resist 326 comprises a thermally curable material that can be cured by a solvent evaporation curing process including thermal heating or infrared illumination heating. The resist 326 can be deposited on the surface 306 using liquid material casting, spin coating, liquid spraying, dry powder coating, screen printing, doctor blade coating, physical vapor deposition (PVD), chemical vapor deposition (CVD), flowable CVD (FCVD), or atomic layer deposition (ALD) processes.

[0022] At operation 204, residual layer 318 is removed. In one embodiment, residual layer 318 is removed by plasma ashing (commonly referred to as plasma slagging) using oxygen-containing (O2) plasma, fluorine-containing (F2) plasma, chlorine-containing (Cl2) plasma, and methane-containing (CH4) plasma. In another embodiment, radio frequency (RF) power is applied to O2 and an inert gas, such as argon (Ar) or nitrogen (N), until residual layer 318 is removed. Figure 3C As shown, the reflector 320 has reflection depths 328 and 330 extending from the top reflector surface 322 to the surface 306 of the substrate 304. In one embodiment, the reflection depths 328 and 330 are substantially the same. In another embodiment, the reflection depths 328 and 330 are different.

[0023] At operation 205, coating 322 is deposited on surface 306 of substrate 304. In one embodiment, as... Figure 3D and Figure 3EAs shown, coating 322 is deposited on surface 306 of substrate 304 and the remaining protrusions of negative waveguide structure 312. Coating 322 has a second refractive index that substantially matches or is greater than the first refractive index. Coating 322 includes at least one of spin-coated glass (SOG), flowable SOG, sol-gel, organic nanoimprintable materials, inorganic nanoimprintable materials, and mixed (organic and inorganic) nanoimprintable materials, such as silicon oxide (SiOC), titanium dioxide (TiO2), silicon dioxide (SiO2), vanadium oxide (VOC), etc. x The coating 322 can be deposited on surface 306 using at least one of the following materials: alumina (Al2O3), indium tin oxide (ITO), zinc oxide (ZnO), tantalum pentoxide (Ta2O5), silicon nitride (Si3N4), titanium nitride (TiN), and / or zirconium dioxide (ZrO2). Liquid casting, spin coating, liquid spraying, dry powder coating, screen printing, doctor blade coating, PVD, CVD, FCVD, or ALD processes can be used. Furthermore, coating 322, such as a SiOC coating, can undergo UV curing or thermal curing. Figure 3D As shown, in one embodiment, excess coating 322 may be present. In this embodiment, excess coating 322 is removed using material thermal reflow or etching. Figure 3E As shown, coating 322 is flush with the remaining protrusions of negative waveguide structure 312, or extends above substrate 304 to the same height as the remaining protrusions of negative waveguide structure 312. In one embodiment, coating 322 is liquid-deposited, and excess coating 322 is removed by mechanical planarization.

[0024] The refractive index of the coating 322 is tuned based on a first refractive index of the substrate 304 and the intensity of the grating, such as the plurality of gratings 108 obtained by the input coupling region 102 and / or the plurality of gratings 110 obtained by the output coupling region 106 formed by method 200. The refractive index of the coating 322 is tuned based on the first refractive index of the substrate 304 and the intensity of the grating to control the input and output coupling of light and facilitate light propagation through the waveguide structure 300. For example, the material of the surface 306 of the substrate 304 has a first refractive index between about 1.5 and about 2.5, and the material 322 of the coating has a second refractive index between about 1.5 and about 2.5. By matching the refractive indices of the material used to manufacture the substrate 304 and the material of the coating 322, light propagation can be achieved through both the materials of the substrate 304 and the coating 322 without significant light refraction at the interface between the surface 306 of the substrate 304 and the material of the coating 322. By utilizing a coating 322 with a refractive index greater than that of the material used to manufacture substrate 304, more light will be coupled into and out of waveguide structure 300 through the light receiving angle. The materials of substrate 304 and coating 322 together constitute waveguide structure 300. Compared to the refractive index of air (1.0), by utilizing a material with a refractive index between about 1.5 and about 2.5 for substrate 304, total internal reflection or at least a high degree of reflection is achieved to facilitate light propagation through waveguide structure 300.

[0025] At operation 206, resist 326 is removed to form waveguide structure 300. In one embodiment, resist 326 is removed by plasma ashing using O2-containing plasma, F2-containing plasma, Cl2-containing plasma, and / or CH4-containing plasma. In another embodiment, RF power is applied to O2 and an inert gas, such as argon (Ar) or nitrogen (N), until resist 326 is removed. Figure 3FAs shown, waveguide structure 300 includes region 334. In one embodiment, region 334 corresponds to at least one of the input coupling region 102, waveguide region 104, and output coupling region 106 of waveguide combiner 100. Region 334 includes a plurality of gratings 336. In one embodiment, region 334 includes a plurality of gratings 336 corresponding to at least one of the plurality of gratings 108 in input coupling region 102, a plurality of gratings 110 in output coupling region 106, and waveguide region 104. In one embodiment, grating 336 has a top surface 338 parallel to the surface 306 of substrate 304, and sidewall surfaces 340. In one embodiment, each of the sidewall surfaces 340 of grating 336 is oriented perpendicular to the surface 306 of substrate 304. In another embodiment, each of the sidewall surfaces 340 of grating 336 is angled relative to the surface 306 of substrate 304. In yet another embodiment, a portion of the sidewall surface 340 is vertically oriented, and a portion of the sidewall surface 340 of the grating 336 is angled relative to the surface 306 of the substrate 304. In one embodiment, the sidewall surface 340 is angled between approximately 15 degrees and approximately 75 degrees. The grating 336 has depths 342 and 344 extending from the surface 306 of the substrate 304 to the top surface 338. In one embodiment, depths 342 and 344 are substantially the same. In another embodiment, depths 342 and 344 are different.

[0026] Figure 4 This is an example used in manufacturing such as Figures 5A to 5D A flowchart illustrating the operation of method 400 with waveguide structure 500 is provided. In one embodiment, waveguide structure 500 corresponds to at least one of the input coupling region 102, waveguide region 104, and / or output coupling region 106 of waveguide combiner 100. In another embodiment, waveguide structure 500 corresponds to a mother plate of at least one of the input coupling region 102, waveguide region 104, and output coupling region 106 of waveguide combiner 100. At operation 401, coating 322 is deposited on the negative waveguide structure 512 of mold 308. Figure 5A As shown, in one embodiment, the deposited coating 322 conforms to the negative waveguide structure 512 of the imprint 308. Figure 5B As shown, in one embodiment, the deposited coating 322 is substantially planar with respect to the negative waveguide structure 512 of the impression 308. Therefore, planarization of the coating 322 is not necessarily performed at optional operation 402. At optional operation 402, in one embodiment, planarization of the coating 322 includes mechanical leveling by gravity, thermal reflow, or chemical mechanical polishing (CMP).

[0027] The mold 308 is molded from the waveguide mother plate and may be made of a translucent material (such as fused silica or PDMS) to allow the coating 322 to cure by exposure to electromagnetic radiation (such as IR radiation or UV radiation). In one embodiment, the mold 308 includes a rigid backing sheet, such as a glass sheet, to increase mechanical strength to facilitate the deposition and planarization of the coating 322.

[0028] Coating 322 includes at least one of SOG, flowable SOG, sol-gel, organic nanoimprintable materials, inorganic nanoimprintable materials, and mixed (organic and inorganic) nanoimprintable materials, such as SiOC-containing materials, TiO2-containing materials, SiO2-containing materials, and VO2-containing materials. x The coating material includes at least one of the following: Al2O3-containing materials, ITO-containing materials, ZnO-containing materials, Ta2O5-containing materials, Si3N4-containing materials, TIN-containing materials, and ZrO2-containing materials. The coating 322 can be deposited using liquid casting, spin coating, liquid spraying, dry powder coating, screen printing, doctor blade coating, PVD, CVD, FCVD, or ALD processes. In one embodiment, the coating material is doped with a dopant material to lower the melting temperature of the coating material and allow improved flow of the coating material during planarization. The dopant material may include phosphorus (P)-containing materials and / or boron (B)-containing materials that allow for thermal reflow at lower temperatures.

[0029] like Figure 5A and Figure 5B As shown, the negative waveguide structure 512 includes an inverted region 516. The inverted region 516 includes a plurality of reflective gratings 520 to form at least one of a plurality of gratings 108 in the input coupling region 102, a plurality of gratings 110 in the output coupling region 106, and a waveguide region 104. In one embodiment, the reflective grating 520 has an inverted top surface 522 parallel to the bottom surface 521 of the mold 308, an inverted sidewall surface 524, and an inverted bottom surface 523 parallel to the bottom surface 521 of the mold 308. In one embodiment, each of the inverted sidewall surfaces 524 of the reflective grating 520 is oriented perpendicular to the bottom surface 521 of the mold 308. In another embodiment, each of the inverted sidewall surfaces 524 of the reflective grating 520 is angled relative to the bottom surface 521 of the mold 308. In another embodiment, the reflector 520 is a blazed angled reflector 502, comprising an anti-blazed surface 502 angled relative to the bottom surface 521 of the mold 308 and an anti-sidewall surface 524 oriented perpendicular to the bottom surface 521 of the mold 308. In yet another embodiment, the anti-area 516 includes a blazed angled reflector 502 and a plurality of reflectors 520, wherein a portion of the anti-sidewall surface 524 is vertically oriented, and a portion of the anti-sidewall surface 524 of the reflector 520 is angled relative to the bottom surface 521 of the mold 308. Figure 5A and Figure 5B As shown, the reflector 520 has reflection depths 528 and 530 extending from the top surface 522 of the impression 308 to the bottom surface 521. In one embodiment, reflection depths 528 and 530 are substantially the same. In another embodiment, reflection depths 528 and 530 are different.

[0030] At operation 403, such as Figure 5C As shown, coating 322 is bonded to surface 306 of portion 302 of substrate 304. Optical adhesive 501 is used to bond coating 322 to surface 306 of substrate 304. In one embodiment, optical adhesive 501 may contain a transparent metal oxide material or a transparent acrylic polymer. Optical adhesive 501 has a third refractive index.

[0031] The coating 322 has a second refractive index that substantially matches or is greater than the first refractive index of the substrate 304. The second refractive index of the coating is tuned based on the first refractive index of the substrate 304 and the intensity of the gratings, such as the plurality of gratings 108 obtained by the input coupling region 102 formed by method 400 and / or the plurality of gratings 110 obtained by the output coupling region 106. The refractive index of the coating 322 is tuned based on the first refractive index of the substrate 304 and the intensity of the gratings to control the input and output coupling of light and to facilitate light propagation through the waveguide structure 500. Furthermore, the optical adhesive 501 has a third refractive index that substantially matches the first and second refractive indices. For example, the material of the surface 306 of the substrate 304 has a first refractive index between about 1.5 and about 2.5, the material of the optical adhesive 501 has a third refractive index between about 1.5 and about 2.5, and the material 322 of the coating has a second refractive index between about 1.5 and about 2.5. By matching the refractive indices of the materials used to manufacture substrate 304, optical adhesive 501, and coating 322, light propagation can be achieved through these materials without significant light refraction at the interface between them. By utilizing the material of coating 322, which has a refractive index greater than that of the material used to manufacture substrate 304, more light will be coupled into and out of waveguide structure 500 through the light receiving angle. Compared to the refractive index of air (1.0), by utilizing materials with a refractive index between approximately 1.5 and approximately 2.5 for both substrate 304 and optical adhesive 501, total internal reflection or at least a high degree of reflection is achieved to facilitate light propagation through waveguide structure 500.

[0032] At operation 404, the imprint 308 is released to form waveguide structure 500. For example... Figure 5DAs shown, the waveguide structure 500 includes a region 534. In one embodiment, region 534 corresponds to at least one of the input coupling region 102, waveguide region 104, and output coupling region 106 of the waveguide combiner 100. Region 534 includes a plurality of gratings 536. In one embodiment, the plurality of gratings 536 corresponds to at least one of the plurality of gratings 108 in the input coupling region 102, the plurality of gratings 110 in the output coupling region 106, and the waveguide region 104. In one embodiment, the grating 536 has a top surface 538 parallel to the surface 306 of the substrate 304, and sidewall surfaces 540. In one embodiment, each of the sidewall surfaces 540 of the grating 536 is oriented perpendicular to the surface 306 of the substrate 304. In another embodiment, each of the sidewall surfaces 540 of the grating 536 is angled relative to the surface 306 of the substrate 304. In another embodiment, grating 536 is a blazed angled grating, comprising a blazed surface 506 angled relative to surface 306 of substrate 304 and a sidewall surface 540 oriented perpendicular to surface 306 of substrate 304. In yet another embodiment, region 534 includes a blazed angled grating and grating 536, wherein a portion of sidewall surface 540 is oriented perpendicularly, and a portion of sidewall surface 540 of grating 536 is angled relative to surface 306 of substrate 304. Grating 536 has depths 542, 544 extending from optical adhesive 501 to top surface 538. In one embodiment, depths 542 and 544 are substantially the same. In another embodiment, depths 542 and 544 are different.

[0033] In summary, this paper describes a method for fabricating a waveguide combiner. The method provides a waveguide combiner having an input coupling region, a waveguide region, and an output coupling region formed of inorganic or hybrid (organic and inorganic) materials that define a fine grating. Compared to organic resists that cannot be imprinted to form a grating with an optimal refractive index for propagating light through the waveguide, inorganic or hybrid waveguide structures are stable, have low optical absorption loss, and possess an optimal refractive index for propagating light through the waveguide combiner.

[0034] Although the foregoing is directed to examples of this disclosure, other and further examples are contemplated without departing from the basic scope of this disclosure, and the scope of the examples is determined by the appended claims.

Claims

1. A method for manufacturing a waveguide structure, comprising: An imprint is applied to a resist, the imprint having: a positive waveguide pattern having a plurality of angled imprint structures, the imprint forming a negative waveguide structure, the negative waveguide structure including a region having a residual layer and containing a plurality of reflective gratings, the resist being disposed on a portion of the surface of a substrate having a first refractive index, and a portion of the sidewall surface of each of the plurality of reflective gratings corresponding to the angled imprint structure being angled relative to the surface of the substrate. The resist cured on the surface of the substrate; Release the impression; Remove the residual layer; A coating having a second refractive index is deposited, the second refractive index being matched with or greater than the first refractive index of the surface of the substrate; as well as A waveguide structure is formed, the waveguide structure including a region having a plurality of gratings, wherein each of the plurality of gratings has a sidewall surface that is not perpendicular to the surface of the substrate and is angled, wherein the coating comprises a silicon oxide (SiOC) material and a vanadium (IV) oxide (VO) material. x The waveguide structure comprises at least one of the following materials: aluminum oxide (Al2O3), zinc oxide (ZnO), silicon nitride (Si3N4), titanium nitride (TiN), and zirconium dioxide (ZrO2), and the waveguide structure includes the materials of the substrate and the coating.

2. The method of claim 1, wherein the region is at least one of the input coupling region, waveguide region, and output coupling region of the waveguide combiner.

3. The method of claim 2, wherein the plurality of gratings is a plurality of gratings of at least one of the input coupling region and the output coupling region.

4. The method of claim 1, wherein each of the plurality of reflectors has a different reflective depth.

5. A method for manufacturing a waveguide structure, comprising: A coating having a second refractive index is deposited on a negative waveguide structure of an imprint, the negative waveguide structure having multiple imprint structures of different depths, the second refractive index being matched with or greater than a first refractive index of a substrate, and the negative waveguide structure including a region containing multiple reflective gratings, the multiple reflective gratings corresponding to the multiple imprint structures of different depths and each reflective grating having a different reflective depth. Planarize the coating; The coating is bonded to a portion of the surface of the substrate; as well as The stencil is released to form a waveguide structure comprising a region containing a plurality of gratings, each grating having a different depth, wherein the coating comprises a silicon oxide (SiOC) material and a vanadium (IV) oxide (VO) material. x The material contains at least one of the following: aluminum oxide (Al2O3), zinc oxide (ZnO), silicon nitride (Si3N4), titanium nitride (TiN), and zirconium dioxide (ZrO2).

6. The method of claim 5, wherein the deposition of the coating comprises liquid material casting, spin coating, liquid spraying, dry powder coating, screen printing, doctor blade coating, physical vapor deposition (PVD), chemical vapor deposition (CVD), flowable CVD (FCVD), or atomic layer deposition (ALD).

7. The method of claim 5, wherein the plurality of gratings are at least one of the input coupling region and the output coupling region of the waveguide combiner.

8. The method of claim 5, wherein the coating is bonded to the surface of the substrate using an optical adhesive, and the optical adhesive has a third refractive index that substantially matches the first and second refractive indices.

9. The method of claim 5, wherein the plurality of gratings includes sidewall surfaces inclined relative to the surface of the substrate.

10. A method for manufacturing a waveguide structure, comprising: A coating having a second refractive index between 1.5 and 2.5 is deposited on a negative waveguide structure of an imprint, the negative waveguide structure comprising a plurality of imprint structures of different depths, the coating being substantially planar on the negative waveguide structure, the second refractive index matching or greater than a first refractive index of the substrate between 1.5 and 2.5, and the negative waveguide structure comprising an input coupling region and an output coupling region, and a plurality of reflective gratings of different depths corresponding to the plurality of imprint structures of different depths, each reflective grating having a different reflective depth extending from the top surface of each reflective grating to the bottom surface of the imprint; The coating is bonded to a portion of the surface of the substrate, the surface of which is provided with an optical adhesive having a third refractive index that substantially matches the first and second refractive indices; as well as The mold is released to form a waveguide structure having a region comprising a plurality of gratings, each of the plurality of gratings having a different depth extending from the top surface of each grating to an optical adhesive disposed on the substrate. The coating includes silicon carbide (SiOC) materials and vanadium (IV) oxide (VO) materials. x The material contains at least one of the following: aluminum oxide (Al2O3), zinc oxide (ZnO), silicon nitride (Si3N4), titanium nitride (TiN), and zirconium dioxide (ZrO2).

11. The method of claim 10, wherein the optical adhesive comprises a transparent metal oxide material or a transparent acrylic polymer, and wherein the third refractive index is between 1.5 and 2.

5.

12. The method of claim 10, wherein the plurality of gratings are at least one of the input coupling region and the output coupling region of the waveguide combiner.

13. The method of claim 12, wherein the plurality of gratings includes a top surface parallel to the surface of the substrate and a sidewall surface inclined by an amount relative to the surface of the substrate.

14. The method of claim 13, wherein the plurality of gratings are blazed angled gratings, the blazed angled gratings comprising a blazed surface angled relative to the surface of the substrate and a sidewall surface oriented perpendicular to the surface of the substrate.

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