Waveguide with high refractive index material and method for fabricating the same.

Abstract

To provide a waveguide with a suitable high refractive index material and a method for processing the same. [Solution] A waveguide and a method for patterning the waveguide are disclosed, made of a material having a refractive index greater than or equal to 1.8. The patterned waveguide made of a material having a refractive index greater than or equal to 1.8 can be incorporated into a display device, such as a wearable display device, to project a virtual image onto the viewer.

Description

[Technical Field]

[0001] This disclosure relates to optical systems, including augmented reality imaging and visualization systems. [Background technology]

[0002] Modern computing and display technologies are driving the development of systems for so-called "virtual reality" or "augmented reality" experiences, in which digitally reproduced images or parts thereof are presented to the user in a manner that appears, or can be perceived, as real. Virtual reality, or "VR," scenarios typically involve the presentation of digital or virtual image information without transparency to other real-world visual inputs, while augmented reality, or "AR," scenarios typically involve the presentation of digital or virtual image information as an extension of the visualization of the real world around the user. Mixed reality, or "MR," scenarios are a type of AR scenario that typically involves virtual objects integrated into and responding to the natural world. For example, an MR scenario may include AR image content that appears blocked by, or is perceived to interact with, objects in the real world in a different way.

[0003] Referring to Figure 1, an augmented reality scene 10 is depicted. The user of the AR technology sees a real-world park-like setting 20 featuring people, trees, buildings in the background, and a concrete platform 30. The user also perceives "virtual content" such as a robot figure 40 standing on the real-world platform 30 and a flying cartoon-like avatar character 50 that looks like an anthropomorphic bumblebee. These elements 50 and 40 are "virtual" in that they do not exist in the real world. The human visual perception system is complex, and it is difficult to produce AR technology that facilitates a comfortable, natural, and rich presentation of virtual image elements among other virtual or real-world image elements.

[0004] The systems and methods disclosed herein address various challenges related to AR or VR technologies. [Overview of the project] [Means for solving the problem]

[0005] A head-mounted display system may be configured to project light onto the user's eyes and display augmented reality image content within the user's field of view. The head-mounted display system may include a frame configured to be supported on the user's head. The head-mounted display system may also include an eyepiece positioned on the frame. At least a portion of the eyepiece may be transparent, and / or the transparent portion may be positioned in front of the user's eyes when the user wears the head-mounted display, so as to allow light from the environment in front of the user to pass through to the user's eyes and provide a view of that environment in front of the user. The eyepiece may include one or more waveguides positioned to direct light into the user's eyes and form augmented reality image content.

[0006] Various embodiments of a head-mounted display system include a projector having at least one pupil or subpupil that outputs light (e.g., image light) having multiple color or wavelength ranges (e.g., two or three color or wavelength ranges) within at least one pupil or subpupil. Different colors or wavelengths within the multiple wavelength ranges may include one or more colors or wavelengths. In some embodiments, the head-mounted display system includes a waveguide assembly comprising multiple waveguides stacked across each other and configured to receive light having multiple color or wavelength ranges output from at least one pupil of the projector. Different waveguides within the multiple waveguides may include internally coupled optical elements configured to internally couple one of the colors or wavelength ranges of light from the light output from the pupil of the projector. One or more waveguides made of a material with a relatively high refractive index (e.g., a refractive index above and / or above or equal to about 1.8) can, advantageously, expand the field of view compared to waveguides made of glass and / or materials with a refractive index below about 1.8. In addition, in various embodiments of the display device, different colors or wavelengths of light (e.g., red, green, and / or blue wavelengths of light) can be internally coupled in a single waveguide made of a material with a relatively high refractive index (e.g., a refractive index higher than that of glass and / or a refractive index higher than or equal to about 1.8). In one or more embodiments, two or more colors (e.g., two or three colors) can be coupled in a single waveguide made of a material with a relatively high refractive index, propagate through it, and maintain a wide field of view (e.g., a refractive index of about 1.8 or higher). Therefore, the various embodiments of the display device considered herein include one or more waveguides made of a material with a refractive index higher than that of glass. For example, one or more waveguides in the various embodiments of the display device considered herein may be made of lithium niobate (LiNbO3), lithium tantalate (LiTaO3), diamond, silicon carbide (SiC), and other similar materials having a refractive index of about 1.8 or higher and an absorption coefficient of less than 0.001.In various embodiments, one or more waveguides in various embodiments of the display devices considered herein may be made of a material that is transparent to visible light and has a refractive index greater than that of glass. This application also describes a system and method for fabricating a grating on one or more surfaces of a waveguide made of a material that is transparent to visible light and has a refractive index greater than that of glass, such as lithium niobate (LiNbO3), silicon carbide (SiC), diamond, and other similar materials. Waveguides made of materials such as diamond and SiC, having a hardness coefficient (e.g., about 9-10 Mohs), may have the additional advantage of being scratch-resistant and / or less prone to breakage. In some implementations, the waveguide and the grating formed therein are made of x-cut lithium niobate.

[0007] Each of the systems, methods, and devices disclosed herein has several innovative aspects, none of which is solely responsible for the desirable attributes disclosed herein. Various exemplary systems and methods are provided below. (Examples) (Example I)

[0008] Example 1: A method for manufacturing a diffractive optical element, The steps include providing a substrate made of a material that is transparent to visible light and has a refractive index greater than 2.0, The steps include: arranging a patternable layer across the surface of the substrate, A step of forming a pattern on a patternable layer, wherein the pattern comprises multiple surface relief features having different heights, A step of etching the surface of a substrate through a patternable layer to process a structure on the surface of the substrate, wherein the structure has diffractive features configured to diffract visible light, Methods that include...

[0009] Example 2: The method according to Example 1, wherein the transparent material consists of at least one of LiNbO3, LiTaO3, or BaTiO3.

[0010] Example 3: The transparent material is the method described in Example 2, comprising an X-cut LiNbO3 wafer.

[0011] Example 4: The method according to any of the above embodiments, further comprising the step of arranging a layer between the substrate and the patternable layer across the substrate.

[0012] Example 5: The method according to Example 4, wherein the layer between the substrate and the patternable layer is a dielectric layer.

[0013] Example 6: The method according to Example 4, wherein the layer between the substrate and the patternable layer is a conductive layer.

[0014] Example 7: The method according to Example 4, 5, or 6, wherein the layer between the substrate and the patternable layer is made of a transparent oxide.

[0015] Example 8: The method according to Example 4 or 6, wherein the layer between the substrate and the patternable layer is made of a conductive oxide.

[0016] Example 9: The method according to Example 4, wherein the layer between the substrate and the patternable layer consists of at least one of SiC, TiO2, ZrO2, Si3N4, or SiO2.

[0017] Example 10: The method according to any one of Examples 4-9, wherein the layer between the substrate and the patternable layer is made of a material having a refractive index of 1.45 to 3.5.

[0018] Example 11: The method according to any one of Examples 4-9, wherein the layer between the substrate and the patternable layer is made of a material having a refractive index of 2.0 or higher.

[0019] Example 12: The method according to any one of Examples 4, 6, 8, 10, or 11, wherein the layer between the substrate and the patternable layer consists of a material configured to dissipate electrostatic charge.

[0020] Example 13: The method according to any one of the above examples, further comprising the step of disposing an adhesion promoter layer across the substrate prior to the step of disposing the patternable layer.

[0021] Example 14: The method according to Example 13, wherein the adhesion promoter layer has a thickness of 10 nm or less.

[0022] Example 15: The method according to Example 13 or 14, wherein the adhesion promoter layer is configured to covalently bond with the patternable layer.

[0023] Example 16: The method according to Example 13 or 14, wherein the adhesion promoter layer is configured to crosslink with the substrate.

[0024] Example 17: The method according to any one of the above examples, wherein the patternable layer has a refractive index of less than 2.0.

[0025] Example 18: The method according to any one of the above examples, further comprising the step of exposing the surface of the substrate to an ionization device prior to the step of disposing the patternable layer.

[0026] Example 19: The method according to Example 18, wherein the ionization device comprises bipolar clean air ionization.

[0027] Example 20: The method according to Example 18, wherein the ionization device comprises positive or negative ions.

[0028] Example 21: The method according to any one of the above examples, further comprising the step of bringing a charged surface close to or into contact with the surface of the substrate, thereby dissipating surface charge.

[0029] Example 22: The method according to any of the above examples, further comprising the step of mounting the substrate on an electrically grounded mounting area, thereby dissipating surface charge.

[0030] Example 23: The method according to any of the above examples, further comprising the step of depositing a metal layer over a substrate to thereby dissipate surface charge.

[0031] Example 24: The method according to Example 23, wherein the metal layer consists of iridium, chromium, or nickel.

[0032] Example 25: The method according to any of the above examples, wherein the step of depositing the patternable layer includes the step of jet depositing the patternable layer over a surface.

[0033] Example 26: The method according to any of the above examples, wherein the patternable layer is deposited non-uniformly across the surface, and areas of the surface where the patternable layer is thicker produce higher surface relief features than areas of the surface where the patternable layer is thinner.

[0034] Example 27: The step of etching the surface of the substrate is as follows:

[0035] The method according to any of the above embodiments, comprising the step of exposing a patternable layer to a first etching solution configured to etch the patternable layer.

[0036] Example 28: The method according to Example 27, further comprising the step of exposing the surface of a substrate to a second etching solution, wherein the second etching solution is configured to etch the substrate.

[0037] Example 29: The method according to Example 27, further comprising the step of exposing a layer of dielectric material, which is placed on a substrate, to a second etching solution configured to etch the layer of dielectric material.

[0038] Example 30: The method according to Example 29, further comprising the step of exposing the surface of a substrate to a third etching solution configured to etch the substrate material.

[0039] Example 31: The method according to any of the above examples, wherein the step of forming the pattern on the patternable layer includes the step of imprinting the pattern within the patternable layer.

[0040] Example 32: The method according to Example 31, wherein the step of imprinting a pattern onto a patternable layer includes the step of bringing the patternable layer into contact with the patterned template.

[0041] Example 33: The method according to any of the above examples, wherein the step of forming the pattern on the patternable layer includes the step of patterning using photolithography.

[0042] Example 34: The substrate is made of a dielectric, as described in any of the above examples.

[0043] Example 35: The patternable layer is made of a polymer, according to any of the above examples.

[0044] Example 36: The method according to any of the above examples, wherein the patternable layer is made of a resist.

[0045] Example 37: The method according to Example 36, wherein the patternable layer is made of a photoresist.

[0046] Example 38: The method according to any of the above embodiments, further comprising the step of integrating a diffractive optical element into a head-mounted display.

[0047] Example 39: A method for manufacturing a diffractive optical element, The steps include providing a substrate made of a material that is transparent to visible light and has a refractive index greater than 2.0, The steps include: placing different amounts of patternable material across different areas on the surface of a substrate; The process involves etching the surface of a substrate through a patternable material to create a structure with different heights on the substrate surface, thereby forming diffraction features. Methods that include...

[0048] Example 40: The method according to Example 39, wherein a surface area having more patternable material produces higher surface relief features than a surface area having less patternable material.

[0049] Example 41: A method for manufacturing a diffractive optical element, The steps include providing a substrate made of a material that is transparent to visible light and has a refractive index greater than 2.0, A step of arranging patternable materials of different compositions over different laterally spaced regions on the surface of a substrate, wherein the patternable materials of different compositions have etching solutions with different etching rates. The process involves etching the surface of a substrate through a patternable material using an etching solution to create a structure with different heights on the substrate surface, thereby forming diffraction features. Methods that include...

[0050] Example 42: A display device, A waveguide stack comprising multiple waveguides, wherein at least one of the waveguides is made of a material transparent to visible light and having a refractive index greater than 2.0. Equipped with, A display device in which at least one of the plurality of waveguides comprises a first main surface, a second main surface, and a plurality of thinner edges, the first main surface having a plurality of diffraction features having different heights.

[0051] Example 43: The display device according to Example 42, wherein the second main surface has multiple diffraction features offset from multiple diffraction features of the first main surface.

[0052] Example 44: The display device according to Example 42 or 43, wherein the transparent material comprises one or more of LiNbO3, LiTaO3, SiC, or TiO2.

[0053] Example 45: A frame configured to be supported above the user's head, An eyepiece with a waveguide stack positioned on the frame, A display device according to any of Examples 42-44, further comprising the above.

[0054] Example 46: The display device includes a head-mounted display.

[0055] Example 47: A method for manufacturing a diffractive optical element, The steps include providing a substrate made of a material that is transparent to visible light and has a refractive index greater than 1.79, The steps include: arranging a patternable layer across the surface of the substrate, A step of patterning a patternable layer, wherein the pattern has multiple features, and A step of etching the surface of a substrate through a patternable layer to fabricate a structure on the surface of the substrate, wherein the structure has diffractive features configured to diffract visible light, Methods that include...

[0056] Example 48: The transparent material is the method described in Example 47, comprising LiNbO3 or silicon carbide.

[0057] Example 49: The method according to Example 47 or 48, wherein the step of patterning the patternable layer includes the step of imprinting the patternable layer using an imprint template having multiple features.

[0058] Example 50: The method according to any one of Examples 47-49, further comprising the step of curing a patterned patternable layer.

[0059] Example 51: The method according to any one of Examples 47-50, wherein the step of arranging the patternable layer across the surface of the substrate includes the step of jet depositing the patternable layer across the surface of the substrate.

[0060] Example 52: The method according to any one of Examples 47-51, wherein the surface of the substrate is discharged prior to the step of arranging the patternable layer by at least one of (i) exposing the surface to plasma, (ii) using an ionizer, (iii) bringing a secondary charged surface or a grounded surface close to the surface, or (iv) providing a transparent metal or other conductive coating.

[0061] Example 53: The patternable layer is made of a resist or polymer, as described in any of Examples 47-52.

[0062] Example 54: The method according to any one of Examples 47-53, further comprising the step of placing an adhesion promoter layer across the surface of the substrate prior to the step of placing the patternable layer.

[0063] Example 55: The method according to any one of Examples 47-54, further comprising the step of placing a layer of high refractive index material having a refractive index greater than 1.79 across the surface of a substrate prior to the step of placing a patternable layer, wherein the layer of high refractive index material is made of a material different from the substrate material.

[0064] Example 56: The method according to Example 55, wherein the layer of high refractive index material consists of at least one of titanium dioxide, zirconium dioxide, silicon nitride, or silicon carbide.

[0065] Example 57: The step of etching the surface of the substrate is as follows: The first etching process involves etching the patterned patternable layer to expose the substrate surface between multiple features of the patternable layer, The second etching process involves etching multiple features and the exposed surface of the substrate, thereby processing multiple features onto the substrate surface. The method according to any of Examples 47-56, including the method described above.

[0066] Example 58: The method according to Example 57, wherein the first etching process comprises the step of etching in the presence of at least one of argon, oxygen, and helium, and the second etching process comprises the step of etching in the presence of at least one of fluorine, bromine, argon, or methane.

[0067] Example 59: The method according to any one of Examples 47-58, wherein the step of placing a patternable layer across the surface of a substrate includes the step of placing a plurality of droplets of patternable material across the substrate.

[0068] Example 60: The method according to Example 59, wherein the volumes of multiple droplets of patternable material vary across the surface of the substrate.

[0069] Example 61: The method according to Example 60, wherein the multiple features of the patterned patternable layer have different heights.

[0070] Example 62: The method according to Example 60, wherein the base of the cured patterned patternable layer is tilted.

[0071] Example 63: The method according to Example 60, wherein the spacing between multiple features of the patterned patternable layer varies across the surface of the substrate.

[0072] Example 64: The method according to any of Examples 59-63, wherein multiple structures formed on the surface of the substrate have different heights.

[0073] Example 65: The method according to Example 59, wherein the volume of multiple droplets of the patternable material is constant.

[0074] Example 66: The method according to Example 65, wherein multiple features of the cured patternable layer are of substantially the same height.

[0075] Example 67: The method according to any one of Examples 65-66, wherein the multiple structures formed on the surface of the substrate have a substantially constant height.

[0076] Example 68: A method for manufacturing a diffractive optical element, The steps include providing a substrate made of a material that is transparent to visible light and has a refractive index greater than 1.79, The steps include: arranging a patternable layer across the surface of the substrate, A method comprising the steps of patterning a patternable layer to form a pattern having a plurality of features, wherein the plurality of features of the patterned patternable layer have diffraction features configured to diffract visible light into the substrate so as to be induced therein, or to diffract visible light induced in the substrate out of the substrate.

[0077] Example 69: The transparent material is the method according to Example 68, comprising LiNbO3 or silicon carbide.

[0078] Example 70: The method according to Example 68 or 69, wherein the step of patterning the patternable layer includes the step of imprinting the patternable layer using an imprint template having multiple features.

[0079] Example 71: The method according to any one of Examples 68-71, further comprising the step of curing a patterned patternable layer.

[0080] Example 72: The method according to any one of Examples 68-71, wherein the step of arranging the patternable layer across the surface of the substrate includes the step of jet depositing the patternable layer across the surface of the substrate.

[0081] Example 73: The method according to any one of Examples 68-72, wherein the surface of the substrate is discharged using at least one of (i) exposing the surface to plasma, (ii) an ionizer, (iii) bringing a secondary charged surface or grounded surface close to the surface, or (iv) providing a transparent metal or other conductive coating, prior to the step of placing a patternable layer.

[0082] Example 74: The patternable layer is made of a resist or polymer, as described in any of Examples 68-73.

[0083] Example 75: The method according to any one of Examples 68-74, further comprising the step of placing an adhesion promoter layer across the surface of the substrate prior to the step of placing the patternable layer.

[0084] Example 76: The method according to any one of Examples 68-75, further comprising the step of placing a layer of high refractive index material having a refractive index greater than 1.79 across the surface of a substrate prior to the step of placing a patternable layer, wherein the layer of high refractive index material is made of a material different from the substrate material.

[0085] Example 77: The method according to Example 76, wherein the layer of high refractive index material consists of at least one of titanium dioxide, zirconium dioxide, silicon nitride, or silicon carbide.

[0086] Example 78: The method according to any one of Examples 68-75, wherein the step of placing a patternable layer across the surface of a substrate includes the step of placing a plurality of droplets of patternable material across the substrate.

[0087] Example 79: The method according to Example 78, wherein the volume of multiple droplets of patternable material varies across the surface of the substrate.

[0088] Example 80: The method according to Example 79, wherein the multiple features of the patterned patternable layer have different heights.

[0089] Example 81: The method according to Example 80, wherein the base of the patterned patternable layer is inclined.

[0090] Example 82: The method according to Example 80, wherein the spacing between multiple features of the patterned patternable layer varies across the surface of the substrate.

[0091] Example 83: The method according to Example 78, wherein the volume of multiple droplets of the patternable material is constant.

[0092] Example 84: The method according to Example 83, wherein multiple features of the patterned patternable layer have substantially the same height.

[0093] Example 85: A method for manufacturing a diffractive optical element, The steps include providing a substrate made of a material that is transparent to visible light and has a refractive index greater than 1.79, A step of jet depositing a patternable layer across the surface of a substrate, The steps include: patterning a patternable layer to form a pattern with multiple features; Methods that include...

[0094] Example 86: The transparent material is the method according to Example 85, comprising LiNbO3 or silicon carbide.

[0095] Example 87: The method according to Example 85 or 86, wherein the step of patterning the patternable layer includes a step of imprinting the patternable layer using an imprint template having multiple features.

[0096] Example 88: The method according to any one of Examples 85-87, further comprising the step of curing a patterned patternable layer.

[0097] Example 89: The method according to Example 85 or 88, wherein the surface of the substrate is discharged using at least one of the following prior to the step of placing a patternable layer: (i) exposing the surface to plasma, (ii) an ionizer, (iii) bringing a secondary charged surface or a grounded surface close to the surface, or (iv) providing a transparent metal or other conductive coating.

[0098] Example 90: The patternable layer is made of a resist or polymer, as described in any of Examples 85-89.

[0099] Example 91: The method according to any one of Examples 85-90, further comprising the step of placing an adhesion promoter layer over the substrate prior to the step of placing the patternable layer.

[0100] Example 92: The method according to any one of Examples 85-91, further comprising the step of placing a layer of high refractive index material having a refractive index greater than 1.79 across the surface of a substrate prior to the step of placing a patternable layer, wherein the layer of high refractive index material is made of a material different from the substrate material.

[0101] Example 93: The method according to Example 92, wherein the layer of high refractive index material consists of at least one of titanium dioxide, zirconium dioxide, silicon nitride, or silicon carbide.

[0102] Example 94: The method according to any one of Examples 85-93, wherein the step of jet depositing a patternable layer across a substrate includes the step of jet depositing a plurality of droplets of patternable material across a substrate.

[0103] Example 95: The method according to Example 94, wherein the volumes of multiple droplets of patternable material vary across the surface of the substrate.

[0104] Example 96: The method according to Example 95, wherein the multiple features of the patterned patternable layer have different heights.

[0105] Example 97: The method according to Example 95, wherein the base of the patterned patternable layer is inclined.

[0106] Example 98: The method according to Example 97, wherein the spacing between multiple features of the patterned patternable layer varies across the surface of the substrate.

[0107] Example 99: The method according to Example 94, wherein the volume of multiple droplets of the patternable material is constant.

[0108] Example 100: The method according to Example 99, wherein multiple features of the cured patternable layer have substantially the same height.

[0109] Example 101: The transparent material is the method described in Example 48, comprising LiNbO3.

[0110] Example 102: The transparent material is the method described in Example 48, and contains silicon carbide.

[0111] Example 103: The method according to Example 52, wherein the surface of the substrate is discharged by exposing the surface to plasma prior to the step of placing the patternable layer.

[0112] Example 104: The method according to Example 52, wherein the surface of the substrate is discharged using an ionizer prior to the step of placing the patternable layer.

[0113] Example 105: The method according to Example 52, wherein the surface of the substrate is discharged by bringing a secondary charged surface or a grounded surface close to the surface prior to the step of placing the patternable layer.

[0114] Example 106: The method according to Example 52, wherein the surface of the substrate is discharged by providing a transparent metal or other conductive coating prior to the step of placing the patternable layer.

[0115] Example 107: The first etching process is the method described in Example 57, wherein the substrate is not etched.

[0116] Example 108: The method according to Example 57, wherein the first etching process etches the substrate with a lower etching rate than the second etching process.

[0117] Example 109: The method according to any one of Examples 1-41 and 47-108, further comprising an optical component across the diffractive optical element.

[0118] Example 110: The method according to Example 109, wherein the optical component is in contact with the diffraction feature.

[0119] Example 111: The method according to Example 109, further comprising a planarization layer between the optical component and the diffraction feature.

[0120] Example 112: The method according to Example 109, further comprising a structural stability-providing layer between the optical component and the substrate.

[0121] Example 113: The method according to Example 109, further comprising a planarization layer between the optical component and the substrate.

[0122] Example 114: The method according to any one of Examples 109-113, wherein the optical component is at least 1 centimeter (cm) in spatial range.

[0123] Example 115: The method according to any of Examples 109-113, wherein the optical component is at least several centimeters within the spatial range.

[0124] Example 116: The method according to any one of Examples 109-115, wherein the optical component comprises a refractive optical component.

[0125] Example 117: The method according to any one of Examples 109-115, wherein the optical component comprises a diffractive optical component.

[0126] Example 118: The optical component comprises a lens, as described in any of Examples 109-117.

[0127] Example 119: The method according to Example 118, wherein the lens is at least 1 centimeter (cm) in the spatial range.

[0128] Example 120: The method according to Example 118, wherein the lens is at least several centimeters within the spatial range.

[0129] Example 121: The method according to any one of Examples 118-120, wherein the lens comprises a convex lens.

[0130] Example 122: The method according to any one of Examples 118-120, wherein the lens comprises a concave lens.

[0131] Example 123: The method according to any one of Examples 118-122, wherein the lens comprises a Fresnel lens.

[0132] Example 124: The method according to any one of Examples 1-41 and 47-108, further comprising the step of placing a first layer across the surface of a substrate prior to the step of placing a patternable layer, wherein the first layer is made of a material different from the substrate material.

[0133] Example 125: The method according to any of Examples 124, wherein the first layer consists of a dielectric layer.

[0134] Example 126: The method according to either Example 124 or 125, wherein the first layer is made of a high refractive index material having a refractive index greater than 1.79.

[0135] Example 127: The method according to any one of Examples 124-126, wherein the first layer consists of at least one of titanium dioxide, zirconium dioxide, silicon nitride, or silicon carbide.

[0136] Example 128: The method according to any one of Examples 124-126, wherein the first layer consists of a layer of titanium dioxide.

[0137] Example 129: The method according to any one of Examples 124-128, further comprising an adhesion promoter layer between the first layer and the patternable layer.

[0138] Example 130: The first layer reduces reflection from the substrate, according to any one of Examples 124-129.

[0139] Example 131: The method according to any one of Examples 124-130, further comprising a second layer between the first layer and the patternable material.

[0140] Example 132: The method according to Example 131, wherein the second layer is made of a dielectric material.

[0141] Example 133: The method according to Example 131 or 132, wherein the first layer has a refractive index between that of the substrate and that of the second layer.

[0142] Example 134: The method according to any one of Examples 131-133, further comprising a third layer between the second layer and the patternable material.

[0143] Example 135: The method according to Example 134, wherein the third layer between the second layer and the patternable material is made of a dielectric material.

[0144] Example 136: The method according to Example 134 or 135, wherein the second layer has a refractive index between that of the first layer and that of the third layer.

[0145] Example 137: The method according to any one of Examples 131-136, wherein the first layer is made of titanium dioxide.

[0146] Example 138: The method according to any one of Examples 131-137, wherein the second layer consists of silicon nitride.

[0147] Example 139: The method according to any one of Examples 134-138, wherein the third layer consists of silicon dioxide.

[0148] Example 140: The first and second layers reduce reflection from the substrate, as described in any of Examples 131-139.

[0149] Example 141: The method according to any of Examples 133-139, wherein the first layer, the second layer, and the second layer reduce reflection from the substrate.

[0150] Example 142: The method according to any one of Examples 124-141, further comprising the step of removing the patternable material and reserving the first layer as at least part of the diffraction features.

[0151] Example 143: The method according to any one of Examples 131-141, further comprising the step of removing the patternable material and reserving the first layer and the second layer as at least part of the diffraction features.

[0152] Example 144: The method according to any one of Examples 134-141, further comprising the step of removing the patternable material and reserving the first layer, the second layer, and the third layer as at least part of the diffraction features.

[0153] Example 145: The method according to any of Examples 124-141, further comprising the step of removing the patternable material and reserving the first layer as diffraction features on the substrate, wherein the substrate does not contain corresponding diffraction features to be etched therein.

[0154] Example 146: The method according to any of Examples 131-141, further comprising the step of removing the patternable material and reserving the first and second layers as diffraction features on the substrate, wherein the substrate does not contain the corresponding diffraction features to be etched therein.

[0155] Example 147: The method according to any of Examples 134-141, further comprising the step of removing the patternable material and reserving the first layer, the second layer, and the third layer as diffraction features on the substrate, wherein the substrate does not contain the corresponding diffraction features to be etched therein.

[0156] Example 148: The diffraction feature is the same height as the substrate, according to any of the above examples.

[0157] Example 149: The method according to any of the above examples, wherein the different diffraction features have different heights relative to the substrate.

[0158] Example 150: The method according to Example 149, wherein the different diffraction features have different heights relative to the substrate such that the height gradually increases with lateral position along the substrate.

[0159] Example 151: The method according to any one of Examples 1-41 and 47-108, further comprising a plurality of layers across the surface of the substrate prior to the step of arranging the patternable layer, wherein the plurality of layers consist of a material different from the substrate material.

[0160] Example 152: The method according to Example 151, wherein the plurality of layers consist of a dielectric material.

[0161] Example 152: The method according to Example 151, wherein the plurality of layers consist of at least one layer of titanium dioxide.

[0162] Example 153: The method according to any one of Examples 151-152, wherein the plurality of layers consist of at least one layer of silicon dioxide.

[0163] Example 154: The method according to any one of Examples 151-153, wherein the plurality of layers consist of at least one layer of magnesium fluoride.

[0164] Example 155: The method according to any one of Examples 151-154, wherein the plurality of layers consist of plurality of layers of titanium dioxide.

[0165] Example 156: The method according to any one of Examples 151-155, wherein the plurality of layers consist of plurality of silicon dioxide layers.

[0166] Example 157: The method according to any one of Examples 151-156, wherein the plurality of layers consist of plurality of layers of magnesium fluoride.

[0167] Example 158: The method according to any one of Examples 151-157, wherein the plurality of layers consist of alternating layers of material.

[0168] Example 159: The method according to any one of Examples 151-158, wherein the plurality of layers consist of repeating layers of the material.

[0169] Example 160: The method according to any one of Examples 151-159, wherein the plurality of layers reduce reflection from the substrate.

[0170] Example 161: The method according to any one of Examples 151-160, further comprising the step of removing the patternable material and reserving the plurality of layers as at least part of the diffraction features.

[0171] Example 162: The method of any of Examples 150-159, further comprising the step of removing the patternable material and reserving the plurality of layers as diffraction features on the substrate, wherein the substrate does not contain the corresponding diffraction features etched therein.

[0172] Example 163: The method according to Example 161 or 162, wherein the diffraction feature has the same height as the substrate.

[0173] Example 164: The method according to Example 161 or 162, wherein the different diffraction features have different heights relative to the substrate.

[0174] Example 165: The method according to Example 164, wherein the different diffraction features have different heights relative to the substrate such that the height gradually increases with lateral position along the substrate.

[0175] Example 166: The method according to any one of Examples 1-41 and 47-108, further comprising a first layer made of a material having a refractive index of less than 1.8 across the substrate.

[0176] Example 167: The method according to Example 166, wherein the first layer is made of a resist.

[0177] Example 168: The method according to Example 166 or 167, further comprising a second layer made of a material having a refractive index of at least 1.8 over the first layer.

[0178] Example 169: The method according to Example 168, wherein the second layer is made of TiO2.

[0179] Example 170: The method according to Example 168, wherein the second layer is made of ZrO2.

[0180] Example 171: The method according to Example 168, wherein the second layer is made of Si3N4.

[0181] Example 172: The method according to Example 168, wherein the second layer is made of SiC.

[0182] Example 173: The method according to any of Examples 168-172, wherein the second layer is deposited using angle-of-view deposition.

[0183] Example 174: The method according to any of Examples 168-173, wherein the second layer is mainly located across a surface parallel to the substrate.

[0184] Example 175: The method according to any of Examples 168-173, wherein the amount of material for the second layer on the sidewall of the first layer is very small.

[0185] Example 176: The method according to any one of Examples 168-172, wherein the material of the second layer is on both horizontal and vertical surfaces.

[0186] Example 175: The method according to any one of Examples 168-173, wherein the material of the second layer is present on the first side of the features of the first layer more than on the second side of the features of the first layer.

[0187] Example 176: The method according to any one of Examples 1-41 and 47-108, further comprising one or more anti-reflection layers across the diffractive optical element.

[0188] Example 177: The method according to Example 176, wherein one or more reflection reduction layers are made of a material having a refractive index less than that of the waveguide material.

[0189] Example 178: The method according to Example 176, wherein one or more anti-reflective layers are made of a material having a refractive index of 1.2 to 1.7.

[0190] Example 179: The method according to Example 176, wherein one or more anti-reflective layers consist of magnesium fluoride.

[0191] Example 180: The method according to Example 176 or 179, wherein one or more anti-reflective layers consist of silicon dioxide.

[0192] Example 181: The method according to any one of Examples 176, 179, or 180, wherein one or more anti-reflective layers consist of a resist.

[0193] Example 182: The method according to any of Examples 176-181, wherein multiple anti-reflection layers are arranged across the diffractive optical elements.

[0194] Example 183: The method according to Example 182, wherein one of the anti-reflective layers further away from the substrate has a lower refractive index than one of the anti-reflective layers closer to the substrate.

[0195] Example 184: The method according to Example 182, wherein the anti-reflection layer furthest from the substrate has a lower refractive index than the anti-reflection layer closest to the waveguide, and one or more anti-reflection layers between the anti-reflection layer furthest from the substrate and the anti-reflection layer closest to the substrate have a refractive index between that of the anti-reflection layer furthest from the substrate and that of the anti-reflection layer closest to the substrate.

[0196] Example 185: The method according to any of Examples 176-184, wherein one or more anti-reflective layers are deposited using graze-angle deposition.

[0197] Example 186: The method according to any of Examples 176-185, wherein the sidewalls and grooves of the diffractive optical element consist of one or more anti-reflection layers of a very small amount of material.

[0198] Example 187: The method according to any of Examples 176-184, wherein the anti-reflection layer material is deposited on the surface of the substrate and on the upper surface of multiple diffraction features of the diffractive optical element parallel to the surface of the trench of the diffractive optical element, and the sidewalls of the diffractive optical element consist of a very small amount of anti-reflection layer material.

[0199] Example 188: The method according to any of Examples 176-184, wherein the material for the anti-reflective layer is deposited on both the horizontal and vertical exposed surfaces of multiple features of the optical element.

[0200] Example 189: The anti-reflection layer on the diffractive optical element is planarized, according to any of Examples 176-188.

[0201] Example 190: The method according to any one of Examples 176-189, further comprising a structural stability-providing layer disposed over one or more anti-reflection layers to increase structural stability.

[0202] Example 191: The method according to Example 190, wherein the structural stability-providing layer is made of glass.

[0203] Example 192: The method according to Example 190, wherein the structural stability-providing layer is made of glass having an anti-reflective coating thereon.

[0204] Example 193: The method according to Example 192, wherein the anti-reflective coating on glass consists of alternating layers.

[0205] Example 194: The method according to Example 193, wherein the anti-reflective coating on glass consists of alternating layers of TiO2 and SiO2.

[0206] Example 195: The method according to any one of Examples 176-194, further comprising an additional layer between the reflection reduction layer and the diffraction features of the diffractive optical element.

[0207] Example 196: The method according to any one of Examples 1-41 and 47-108, further comprising an anti-reflective structure arranged across a diffractive optical element, wherein the anti-reflective structure comprises nanostructures configured to reduce reflection.

[0208] Example 197: The method according to Example 196, wherein the nanostructure is directly on the diffractive optical element.

[0209] Example 198: The method according to Example 196, wherein the nanostructure is formed within a coating, arranged across diffractive optical elements.

[0210] Example 199: The coating is the same as in Example 198, but has a lower refractive index than that of the substrate.

[0211] Example 200: The coating is made of a photoresist, as described in Example 198 or 199.

[0212] Example 201: The method according to any one of Examples 1-41 and 47-108, further comprising a reflective grating positioned at the edge of the substrate to receive light propagating to the edge of the substrate by total internal reflection within the substrate.

[0213] Example 202: The method according to Example 201, wherein the reflective grid is configured to redirect light so that it moves away from the edges towards the rear.

[0214] Example 203: The method according to Example 201 or 202, wherein the reflective grating is configured to direct light back toward an exit pupil expander, which is configured to couple light out of the substrate toward the user.

[0215] Example 204: The method according to Example 203, wherein the exit pupil expander comprises a diffractive optical element having a certain pitch, and the reflective grating has a pitch that is about half the pitch of the exit pupil expander.

[0216] Example 205: The reflective grid is metallized according to any of Examples 201-204.

[0217] Example 206: The method according to any one of Examples 1-41 and 47-108, further comprising a light extraction feature positioned at the edge of the substrate and receiving light propagating to the edge of the substrate by total internal reflection within the substrate.

[0218] Example 207: The method according to Example 206, wherein the light extraction feature is configured to extract light outwards from the edge.

[0219] Example 208: The method according to Example 206 or 207, wherein the photoextraction feature is a diffraction feature.

[0220] Example 209: The method according to any one of Examples 206-208, further comprising an absorbing element positioned centrally on the edge and receiving the light extracted by the light extraction feature.

[0221] Example 210: The method according to Example 209, wherein the absorbent element comprises a cuff, collar, cup, or sleeve.

[0222] Example 211: The method according to Example 209 or 210, wherein the absorbing element is made of carbon black.

[0223] Example 212: The method according to any one of Examples 206-208, further comprising an absorption coating on the photoextraction feature.

[0224] Example 213: The method according to any one of Examples 1-41 and 47-108, further comprising at least one structural support layer with the substrate, to provide increased structural strength.

[0225] Example 214: The method according to Example 213, wherein the at least one structural support layer is made of a material having a refractive index of 1.7 or less.

[0226] Example 215: The method according to Example 213 or 214, wherein at least one structural support layer is made of glass.

[0227] Example 216: The method according to Example 215, wherein at least one structural support layer is made of glass having an anti-reflective coating thereon.

[0228] Example 217: The method according to any one of Examples 213-216, wherein at least the structural support layer is directly adjacent to the substrate.

[0229] Example 218: The method according to any one of Examples 213-217, wherein at least one structural support layer fills the spaces between multiple diffraction features of a diffractive optical element.

[0230] Example 219: The method according to any one of Examples 213-216, further comprising air between the at least one structural support layer and the substrate.

[0231] Example 220: The method according to any one of Examples 213-216 and 219, further comprising air between the at least one structural support layer and the plurality of diffraction features.

[0232] Example 221: The method according to any one of Examples 213-216, 219, and 220, further comprising a spacer between the at least one structural support layer and the substrate, thereby providing a gap between the at least one structural support layer and the substrate.

[0233] Example 222: The method according to any one of Examples 213-216 and 219-221, further comprising the step of forming a void, which includes the step of evaporating the polymer layer.

[0234] Example 223: The method according to any one of Examples 213-222, wherein at least one structural support layer provides scratch-resistant functionality.

[0235] Example 224: The method according to any one of Examples 213-223, wherein at least one structural support layer comprises a low refractive index coating.

[0236] Example 225: The method according to any one of Examples 213-224, wherein at least one structural support layer is made of anti-reflective glass.

[0237] Example 226: The method according to any one of Examples 213-225, wherein at least one structural support layer is located on one side of the substrate.

[0238] Example 227: The method according to any one of Examples 213-226, wherein the structural support layer comprises at least two structural support layers.

[0239] Example 228: The method according to Example 227, wherein the at least two structural support layers are arranged on opposite sides of the substrate.

[0240] Example 229: The method according to any of the above examples, wherein the diffraction feature has a height of 10 to 50 nm.

[0241] Example 230: The method according to any of the above examples, wherein the diffraction feature consists of a material having a refractive index of at least 1.8, and the material is different from the material of the substrate.

[0242] Example 231: The method according to any of the above examples, further comprising a planarized layer over the diffraction feature.

[0243] Example 232: The planarized layer has a refractive index of less than 1.6, as described in Example 231.

[0244] Example 233: The method according to any of the above examples, further comprising an anti-reflective coating on the side of the substrate opposite to the diffractive optical elements.

[0245] Example 234: The substrate is colored according to any of the above examples.

[0246] Example 235: The method according to any of the above embodiments, wherein the first and second diffractive optical elements are arranged on the first and second opposing surfaces of the waveguide.

[0247] Example 236: The method according to Example 235, wherein multiple diffraction features of the first diffractive optical element are offset from multiple diffraction features of the second diffractive optical element.

[0248] Example 237: The diffraction feature having a variable height, according to any of the above examples.

[0249] Example 238: The method according to any of the above examples, wherein the diffraction feature has a height that gradually changes with lateral position across the substrate.

[0250] Example 239: The substrate comprises a waveguide, according to any of the above embodiments.

[0251] Example 240: The method according to Example 239, wherein the waveguide is contained within an eyepiece for a head-mounted display.

[0252] Example 241: The method according to Example 239, wherein the waveguide is included in a stack of waveguides within an eyepiece for a head-mounted display.

[0253] Example 242: The method according to Example 240 or 241, wherein the eyepiece is transparent in order to provide the user with a view of the environment in front of the user and the head-mounted display.

[0254] Example 243: The method according to Example 240, 241, or 242, wherein the eyepiece is configured to receive light from an image projector, direct at least a portion of the light towards the user's eye, and direct image content towards the user's eye.

[0255] Example 244: The method according to Examples 240, 241, 242, or 243, wherein the eyepiece is mounted on a frame configured to be worn on the user's head.

[0256] Example 245: A device formed by any of the methods in any of the above examples.

[0257] Example 246: The device according to Example 245, wherein multiple diffraction features or features form a diffraction grating, and the diffraction grating is a blazed grating.

[0258] Example 247: An optical device according to any of the above examples, wherein multiple diffraction features or features are asymmetrical to provide a blazed grating.

[0259] Example 248: An optical device according to any of the above examples, having a material on which multiple diffraction features or features are asymmetrically deposited to provide a blazed lattice.

[0260] Example 249: The optical device according to any of the above embodiments, wherein the substrate includes first and second sides, and only the first side of the substrate includes a diffraction grating.

[0261] Example 250: An optical device according to any of the above examples, wherein the diffraction features or features are arranged in a 1D array.

[0262] Example 251: An optical device according to any of the above examples, wherein diffraction features or features are arranged in a 2D array.

[0263] Example 252: The optical device described in Example 251, wherein the 2D array consists of a square array.

[0264] Example 253: The optical device according to any of the above examples, wherein at least a portion of the etching mask remains on the diffraction feature.

[0265] Example 254: An optical device according to any of the above examples, wherein the polymer remains on the diffraction feature, thereby increasing the height of the diffraction feature.

[0266] Example 255: An optical device according to any of the above examples, wherein the resist remains on the diffraction feature.

[0267] Example 256: The method according to any of the above examples, further comprising the step of leaving at least a portion of the patternable material on the diffraction features.

[0268] Example 257: The method according to any of the above examples, further comprising the step of leaving at least a portion of the etching mask on the diffraction features.

[0269] Example 258: The method according to any of the above examples, further comprising the step of leaving a polymer on the diffraction feature to increase the height of the diffraction feature.

[0270] Example 259: The method according to any of the above examples, further comprising the step of leaving a resist on the diffraction feature to increase the height of the diffraction feature.

[0271] Example 260: Diffraction features are formed within a 1D array, according to any of the above examples.

[0272] Example 261: The diffraction features are formed within a 2D array, according to any of the above examples.

[0273] Example 262: The optical device described in Example 261, wherein the 2D array consists of a square array.

[0274] Example 263: The diffraction features are formed by any of the above examples, according to the method described above.

[0275] Example 264: The diffraction features are formed within a 2D diffraction grating, as described in any of the above examples.

[0276] Example 265: The diffraction features are blazed according to any of the above examples.

[0277] Example 266: The method according to any of the above examples, wherein the diffraction features are asymmetric to provide a blazed lattice.

[0278] Example 267: The method according to any of the above examples, comprising a material on which multiple diffraction features are asymmetrically deposited to provide a blazed lattice.

[0279] Example 268: The optical device according to any of the above embodiments, wherein the substrate includes first and second sides, and only the first side of the substrate includes a diffraction grating.

[0280] Example 269: The plurality of diffraction features receive light from an image source and are included within an internal coupling optical element that is arranged to couple the light into the substrate so as to be guided therein, the optical device according to any of the above examples.

[0281] Example 270: The plurality of diffraction features receive light from an image source that is guided within the substrate and are included within a light dispersing optical element that is arranged to direct the light to an external coupling optical element so as to be coupled out of the substrate, the optical device according to any of the above examples.

[0282] Example 271: The plurality of diffraction features receive light from an image source that is guided within the substrate and are included within a light dispersing optical element that is arranged to diffuse the light out within the waveguide and increase the beam size or eye box size, the optical device according to any of the above examples.

[0283] Example 272: The plurality of diffraction features receive light from an image source that is guided within the substrate and are included within an external coupling optical element that is arranged to couple the light out of the substrate, the optical device according to any of the above examples.

[0284] Example 273: The plurality of diffraction features receive light from an image source that is guided within the substrate and are included within a combined light dispersing / external coupling optical element that is arranged to diffuse the light out in at least two directions and couple the light out of the substrate, the optical device according to any of the above examples.

[0285] Example 274: The plurality of diffraction features receive light from an image source that is guided within the substrate and are included within a combined pupil expander - extractor that is arranged to diffuse the light out and couple the light out of the substrate, the optical device according to any of the above examples.

[0286] Example 275: An optical device according to any of the above embodiments, comprising a blazed diffraction grating, wherein the plurality of diffraction features are configured to preferentially direct light in at least two directions.

[0287] Example 276: The optical device according to any of the above examples, wherein the plurality of diffraction features comprises a blazed diffraction grating blazed in two directions.

[0288] Example 277: The method according to any of the above examples, wherein the plurality of diffraction features are contained within an internally coupled optical element, which is arranged to receive light from an image source and couple the light into the substrate, in such a way that it is guided therein.

[0289] Example 278: The method according to any of the above examples, wherein the plurality of diffraction features are contained within an optically dispersive optical element that receives light from an image source, which is induced within the substrate, and is positioned to direct the light to an external coupling optical element so as to couple out of the substrate.

[0290] Example 279: The method according to any of the above examples, wherein the plurality of diffraction features are contained within an optically dispersed optical element that receives light from an image source, which is induced within the substrate, and is arranged to diffuse the light outward within the waveguide, thereby increasing the beam size or eyebox size.

[0291] Example 280: The method according to any of the above examples, wherein the plurality of diffraction features are contained within an external coupling optical element that receives light from an image source and is arranged to couple the light out of the substrate, the diffraction features being induced within the substrate.

[0292] Example 281: The method according to any of the above examples, wherein the plurality of diffraction features are contained within a combined optical dispersion / external coupling optical element, which is arranged to receive light from an image source, diffuse the light outward in at least two directions, and couple the light outward from the substrate, thereby inducing the diffraction features within the substrate.

[0293] Example 282: The method according to any of the above examples, wherein the plurality of diffraction features are contained within a combined pupil expander-extractor arranged to receive light from an image source, diffuse the light outward, and couple the light outward from the substrate, thereby inducing the light within the substrate.

[0294] Example 283: The method according to any of the above embodiments, comprising a blazed diffraction grating, wherein the plurality of diffraction features are configured to preferentially direct light in at least two directions.

[0295] Example 284: The method according to any of the above examples, wherein the plurality of diffraction features comprises a blazed diffraction grating blazed in two directions. (Example II)

[0296] Example 1: An optical device, A substrate made of a material that is transparent to visible light and has a refractive index greater than 2.0, comprising a waveguide, Multiple diffraction features formed within the substrate, A layer of material arranged across the diffraction features, An optical device equipped with the following features.

[0297] Example 2: The optical device according to Example 1, wherein the substrate material comprises lithium niobate or silicon carbide.

[0298] Example 3: The optical device according to any of the above examples, wherein the substrate material has a refractive index of at least 2.1.

[0299] Example 4: The optical device according to any of the above examples, wherein the substrate material has a refractive index of at least 2.2.

[0300] Example 5: The optical device according to any of the above examples, wherein the substrate material has a refractive index of at least 2.3.

[0301] Example 6: The layer of the material is an optical device according to any of the above examples, having a refractive index less than 1.8.

[0302] Example 7: The layer of the material is an optical device according to any of the above examples, consisting of a photoresist.

[0303] Example 8: The diffraction features are separated by a space that comprises an exposed area of the substrate material, and the optical device is according to any of the above examples.

[0304] Example 9: The diffraction features are separated by a space that is not covered by the layer of the material, and the optical device is according to any of the above examples.

[0305] Example 10: The diffraction features are separated by a space that comprises an exposed area of the substrate material, and the optical device is according to any of the above examples.

[0306] Example 11: The plurality of diffraction features comprises first, second, and third diffraction features that are laterally displaced relative to each other, and the second diffraction feature is disposed between the first diffraction feature and the third diffraction feature, and the optical device is according to any of the above examples.

[0307] Example 12: The layer of the material has different thicknesses over each of the first, second, and third diffraction features, and the optical device is according to Example 11.

[0308] Example 13: The thickness of the layer of the material over the third diffraction feature is higher than the thickness of the layer of the material over the second diffraction feature, and the thickness of the layer of the material over the second diffraction feature is higher than the thickness of the layer of the material over the first diffraction feature, and the optical device is according to Example 11 or 12.

[0309] Example 14: The layer of the material has the same thickness over the first, second, and third diffraction features, and the optical device is according to Example 11.

[0310] Example 15: An optical device according to any one of Examples 11-14, wherein the height of the third diffraction feature is greater than the height of the second diffraction feature, and the height of the second diffraction feature is greater than the height of the first diffraction feature.

[0311] Example 16: An optical device according to any of the above examples, wherein the height of the diffraction feature gradually increases with lateral position.

[0312] Example 17: An optical device according to any of the above examples, wherein the layer of the material has a thickness that gradually increases with lateral position.

[0313] Example 18: The optical device according to any of the above examples, wherein the thickness of the substrate is stepped.

[0314] Example 19: The optical device according to any of the above examples, wherein the thickness of the material layer is stepped.

[0315] Example 20: The optical device according to any of the above examples, wherein the thickness of the substrate gradually increases with respect to the lateral position.

[0316] Example 21: An optical device according to any of the above examples, wherein the height of the diffraction feature is substantially constant with respect to the lateral position.

[0317] Example 22: The optical device according to any of the above examples, wherein the heights of the first, second, and third diffraction features are identical.

[0318] Example 23: An optical device according to any of the above examples, wherein the layer of the material has a thickness that is substantially constant with respect to the lateral position.

[0319] Example 24: An optical device according to any of the above examples, wherein the layers of the material have the same thickness across the first, second, and third diffraction features.

[0320] Example 25: An optical device according to any of the above examples, wherein at least some of the diffraction features have inclined sidewalls.

[0321] Example 26: An optical device according to any of the above examples, wherein at least some of the diffraction features have a trapezoidal cross-section.

[0322] Example 27: The optical device according to any of the above embodiments, wherein the waveguide is contained within an eyepiece for a head-mounted display.

[0323] Example 28: The optical device according to any of the above embodiments, wherein the waveguide is included in a stack of waveguides within an eyepiece for a head-mounted display.

[0324] Example 29: The optical device according to Example 27 or 28, wherein the eyepiece is transparent in order to provide the user with a view of the environment in front of the user and the head-mounted display.

[0325] Example 30: The optical device according to any of Examples 27-29, wherein the eyepiece is configured to receive light from an image projector, direct at least a portion of the light towards the user's eye, and direct image content towards the user's eye.

[0326] Example 31: The optical device according to any of Examples 27-30, wherein the eyepiece is mounted on a frame and configured to be worn on the user's head.

[0327] Example 32: An optical device according to any of the above examples, wherein the plurality of diffraction features are contained within an internally coupled optical element, which is arranged to receive light from an image source and couple the light into the substrate, in such a way that it is guided therein.

[0328] Example 33: The optical device according to any of the above embodiments, wherein the plurality of diffraction features are contained within an external coupling optical element that receives light from an image source, which is induced within the substrate, and is arranged to couple the light out of the substrate to the eyes of a user wearing the head-mounted display.

[0329] Example 34: The optical device according to any of Examples 27-33, wherein the plurality of diffraction features comprises first, second, and third diffraction features, the second diffraction feature being positioned between the first and third diffraction features.

[0330] Example 35: The optical device according to Example 35, wherein the height of the third diffraction feature is greater than the height of the second diffraction feature, and the height of the second diffraction feature is greater than the height of the first diffraction feature.

[0331] Example 36: The optical device according to Example 34 or 35, further comprising a projector positioned relative to a substrate and directing light into the substrate, wherein the projector is positioned closer to the first diffraction feature than to the second diffraction feature.

[0332] Example 37: An optical device according to any of the above examples, wherein the height of the diffraction feature gradually increases with lateral position.

[0333] Example 38: The optical device according to Example 37, further comprising a projector positioned relative to a substrate and directing light into the substrate, wherein the projector is positioned closer to the diffraction feature at a lower height than the diffraction feature at a higher height.

[0334] Example 39: An optical device according to any one of Examples 34-38, wherein the thickness of the layer of the material on the third diffraction feature is greater than the thickness of the layer of the material on the second diffraction feature, and the thickness of the layer of the material on the second diffraction feature is greater than the thickness of the layer of the material on the first diffraction feature.

[0335] Example 40: The optical device according to Example 39, further comprising a projector positioned relative to a substrate and directing light into the substrate, wherein the projector is positioned closer to the first diffraction feature than to the second diffraction feature.

[0336] Example 41: An optical device according to any of the above examples, wherein the layer of the material has a thickness that gradually increases with lateral position.

[0337] Example 42: An optical device according to any of the above embodiments, further comprising a projector positioned on a substrate and directing light into the substrate, wherein the projector is positioned closer to the diffraction feature where the layer of the material is thinner than the diffraction feature where the layer of the material is thicker.

[0338] Example 43: The optical device according to any of the above embodiments, wherein the substrate comprises opposing first and second sides.

[0339] Example 44: The optical device according to Example 43, wherein the optical device is integrated into a head-mounted display, and the second side is positioned closer to the wearer's eyes than the first side when the head-mounted display is worn.

[0340] Example 45: The optical device according to Example 43 or 44, wherein the plurality of diffraction features are arranged on the first side of the substrate.

[0341] Example 46: The optical device according to any one of Examples 43-45, further comprising a plurality of additional diffraction features formed within the substrate on a second opposing side of the substrate.

[0342] Example 47: The optical device according to Example 46, wherein the additional diffraction features are separated by space, and the optical device further comprises an additional layer of material arranged across the additional diffraction features.

[0343] Example 48: An optical device, A substrate made of a material that is transparent to visible light and has a refractive index greater than 2.0, comprising a waveguide, A plurality of diffraction features formed on the substrate, each having a refractive index lower than that of the substrate material, and formed from different materials. A higher refractive index material arranged across the diffraction feature, having a higher refractive index than the material forming the diffraction feature, An optical device equipped with the following features.

[0344] Example 49: The optical device according to Example 48, wherein the substrate material comprises lithium niobate or silicon carbide.

[0345] Example 50: The optical device according to Example 48 or 49, wherein the material constituting the substrate has a refractive index of at least 2.1.

[0346] Example 51: An optical device according to any one of Examples 48-50, wherein the material constituting the substrate has a refractive index of at least 2.2.

[0347] Example 52: An optical device according to any one of Examples 48-50, wherein the material constituting the substrate has a refractive index of at least 2.3.

[0348] Example 53: The optical device according to any of Examples 48-52, wherein the plurality of diffraction features are made of photoresist.

[0349] Example 54: An optical device according to any of Examples 48-53, wherein the plurality of diffraction features have a refractive index of less than 1.8.

[0350] Example 55: The optical device according to any of Examples 48-54, wherein the plurality of diffraction features have a refractive index of about 1.5.

[0351] Example 56: The optical device according to any of Examples 48-55, wherein the plurality of diffraction features have a refractive index of 1.7 to 1.8.

[0352] Example 57: The optical device according to any of Examples 48-56, wherein the higher refractive index material arranged across the diffraction feature has a refractive index of at least 2.1.

[0353] Example 58: The optical device according to any of Examples 48-57, wherein the higher refractive index material arranged across the diffraction feature has a refractive index of at least 2.2.

[0354] Example 59: The optical device according to any of Examples 48-58, wherein the higher refractive index material arranged across the diffraction feature has a refractive index of at least 2.3.

[0355] Example 60: An optical device according to any of Examples 48-59, wherein the higher refractive index material arranged across the diffraction features comprises lithium niobate.

[0356] Example 61: An optical device according to any of Examples 48-59, wherein the higher refractive index material arranged across the diffraction features comprises silicon carbide.

[0357] Example 62: The optical device according to any of Examples 48-61, wherein the plurality of diffraction features comprises a blazed diffraction grating.

[0358] Example 63: The optical device according to any of Examples 48-62, wherein the plurality of diffraction features are shaped asymmetrically.

[0359] Example 64: An optical device according to any of Examples 48-63, wherein more of the high refractive index material is located on the first sidewall of the diffraction feature than on the second sidewall of the diffraction feature.

[0360] Example 65: An optical device according to any of Examples 48-64, wherein more of the high refractive index material is located on the first side of the diffraction feature than on the second side of the diffraction feature.

[0361] Example 66: An optical device according to any of Examples 48-64, wherein at least one of the diffraction features has the high refractive index material on the first side of the diffraction feature, while the second side of the diffraction feature is exposed.

[0362] Example 67: An optical device according to any of the above examples, wherein the diffraction features are arranged in a 1D array.

[0363] Example 68: An optical device according to any of the above examples, wherein the diffraction features are arranged in a 2D array.

[0364] Example 69: An optical device according to any of Examples 1-47, wherein the diffraction feature has an upper surface and side walls arranged centered on the upper surface, and a layer of material is on the upper surface of the diffraction feature.

[0365] Example 70: The optical device according to Example 47, wherein the additional plurality of diffraction features have an upper surface and side walls arranged centered on the upper surface, and the layer of the additional material is on the upper surface of the plurality of additional diffraction features.

[0366] Example 71: The optical device according to any of Examples 48-68, wherein the diffraction feature has an upper surface and side walls arranged centered on the upper surface, and the higher refractive index material is located on the upper surface of the diffraction feature.

[0367] Example 72: The optical device according to any of Examples 48-68, wherein the waveguide is contained within an eyepiece for a head-mounted display.

[0368] Example 73: An optical device according to any of Examples 48-68, wherein the waveguide is contained within a stack of waveguides in an eyepiece for a head-mounted display.

[0369] Example 74: The optical device according to Example 72 or 73, wherein the eyepiece is transparent in order to provide the user with a view of the environment in front of the user and the head-mounted display.

[0370] Example 75: The optical device according to any of Examples 72-74, wherein the eyepiece is configured to receive light from an image projector, direct at least a portion of the light towards the user's eye, and direct image content towards the user's eye.

[0371] Example 76: The optical device according to any of Examples 72-75, wherein the eyepiece is mounted on a frame and configured to be worn on the user's head.

[0372] Example 77: An optical device according to any of the above examples, wherein the plurality of diffraction features are contained within an internally coupled optical element, which is arranged to receive light from an image source and couple the light into the substrate, in such a way that it is guided therein.

[0373] Example 78: The optical device according to any of the above embodiments, wherein the plurality of diffraction features are contained within an externally coupled optical element, which is arranged to receive light from an image source, which is directed from the substrate outward to the eyes of a user wearing the head-mounted display.

[0374] Example 79: An optical device according to any of Examples 1-47, wherein the layer of the material is made of a polymer.

[0375] Example 80: An optical device according to any of Examples 1-47, wherein the layer of the material consists of a resist.

[0376] Example 81: An optical device according to any of Examples 1-47, wherein the layer of the material comprises at least a portion of the etching mask.

[0377] Example 82: An optical device according to any of Examples 1-47, wherein the layer of the material reduces reflection.

[0378] Example 83: An optical device according to any of Examples 1-82, wherein multiple diffraction features form a diffraction grating, and the diffraction grating is a blazed grating.

[0379] Example 84: An optical device according to any of the above examples, wherein the multiple diffraction features are asymmetrical so as to provide a blazed grating.

[0380] Example 85: An optical device according to any of the above examples, having a material on which multiple diffraction features are asymmetrically deposited to provide a blazed lattice.

[0381] Example 86: The optical device according to any of the above embodiments, wherein the substrate includes first and second sides, and only the first side of the substrate includes a diffraction grating.

[0382] Example 87: An optical device according to any of Examples 1-86, wherein the diffraction features are arranged in a 1D array.

[0383] Example 88: An optical device according to any of Examples 1-86, wherein the diffraction features are arranged in a 2D array.

[0384] Example 89: The optical device described in Example 88, wherein the 2D array consists of a square array.

[0385] Example 90: An optical device according to any of the above examples, wherein the plurality of diffraction features are contained within an internally coupled optical element, which is arranged to receive light from an image source and couple the light into the substrate, in such a way that it is guided therein.

[0386] Example 91: An optical device according to any of the above examples, wherein the plurality of diffraction features are contained within a light-dispersive optical element that receives light from an image source, which is induced within the substrate, and is positioned to direct the light to an external coupling optical element so as to couple out of the substrate.

[0387] Example 92: An optical device according to any of the above examples, wherein the plurality of diffraction features are contained within an optically dispersed optical element, which is arranged to receive light from an image source, diffuse the light outward in the waveguide, and increase the beam size or eyebox size, and which is induced within the substrate.

[0388] Example 93: An optical device according to any of the above examples, wherein the plurality of diffraction features are contained within an external coupling optical element that receives light from an image source and is arranged to couple the light out of the substrate, the diffraction features being induced within the substrate.

[0389] Example 94: An optical device according to any of the above examples, wherein the plurality of diffraction features are contained within a combined optical dispersion / external coupling optical element, which receives light from an image source, diffuses the light outward in at least two directions, and couples the light outward from the substrate, the optical device according to any of the above examples.

[0390] Example 95: The optical device according to any of the above embodiments, wherein the plurality of diffraction features are contained within a combined pupil expander-extractor, which is arranged to receive light from an image source, diffuse the light outward, and fuse the light outward from the substrate to the eye of a user wearing the head-mounted display.

[0391] Example 96: An optical device according to any of the above embodiments, comprising a blazed diffraction grating, wherein the plurality of diffraction features are configured to preferentially direct light in at least two directions.

[0392] Example 97: The method according to any of the above examples, wherein the plurality of diffraction features comprises a blazed diffraction grating blazed in two directions. (Example III)

[0393] Example 1: An optical device, A substrate made of a material that is transparent to visible light and has a refractive index greater than 2.0, comprising a waveguide, Multiple diffraction features formed in or on the substrate, An optical device comprising the diffraction features, wherein these features are arranged in a two-dimensional (2D) array to form a 2D diffraction grating.

[0394] Example 2: The optical device according to Example 1, wherein the substrate material comprises lithium niobate or silicon carbide.

[0395] Example 3: The optical device according to any of the above examples, wherein the substrate material has a refractive index of at least 2.1.

[0396] Example 4: The optical device according to any of the above examples, wherein the substrate material has a refractive index of at least 2.2.

[0397] Example 5: The optical device according to any of the above examples, wherein the substrate material has a refractive index of at least 2.3.

[0398] Example 6: An optical device according to any of the above examples, wherein the layer of the material has a refractive index of less than 1.8.

[0399] Example 7: The optical device according to any of the above examples, wherein the diffraction feature is made of a material different from the substrate.

[0400] Example 8: The optical device according to any of the above examples, wherein the diffraction features are separated by space, and the space comprises an exposure region of the substrate material.

[0401] Example 9: An optical device according to any of the above examples, wherein the diffraction features are separated by space, and the space between the diffraction features is not covered by a layer of material.

[0402] Example 10: An optical device according to any of the above examples, wherein the diffraction features are separated by space, and the space between the diffraction features comprises an exposure region of the substrate material.

[0403] Example 11: The optical device according to any of the above examples, wherein the plurality of diffraction features comprises first, second, and third diffraction features that are displaced laterally relative to each other, and the second diffraction feature is positioned between the first and third diffraction features.

[0404] Example 12: The optical device according to Example 11, wherein the layers of the material have different thicknesses across each of the first, second, and third diffraction features.

[0405] Example 13: The optical device according to Example 11 or 12, wherein the thickness of the layer of the material over the third diffraction feature is greater than the thickness of the layer of the material over the second diffraction feature, and the thickness of the layer of the material over the second diffraction feature is greater than the thickness of the layer of the material over the first diffraction feature.

[0406] Example 14: The optical device according to Example 11, wherein the layers of the material have the same thickness across the first, second, and third diffraction features.

[0407] Example 15: An optical device according to any one of Examples 11-14, wherein the height of the third diffraction feature is greater than the height of the second diffraction feature, and the height of the second diffraction feature is greater than the height of the first diffraction feature.

[0408] Example 16: An optical device according to any of the above examples, wherein the height of the diffraction feature gradually increases with lateral position.

[0409] Example 17: An optical device according to any of the above examples, wherein the layer of the material has a thickness that gradually increases with lateral position.

[0410] Example 18: The optical device according to any of the above examples, wherein the thickness of the substrate is stepped.

[0411] Example 19: The optical device according to any of the above examples, wherein the thickness of the material layer is stepped.

[0412] Example 20: The optical device according to any of the above examples, wherein the thickness of the substrate gradually increases with respect to the lateral position.

[0413] Example 21: An optical device according to any of the above examples, wherein the height of the diffraction feature is substantially constant with respect to the lateral position.

[0414] Example 22: The optical device according to any of the above examples, wherein the heights of the first, second, and third diffraction features are identical.

[0415] Example 23: An optical device according to any of the above examples, wherein the layer of the material has a thickness that is substantially constant with respect to the lateral position.

[0416] Example 24: An optical device according to any of the above examples, wherein the layers of the material have the same thickness across the first, second, and third diffraction features.

[0417] Example 25: An optical device according to any of the above examples, wherein at least some of the diffraction features have inclined sidewalls.

[0418] Example 26: An optical device according to any of the above examples, wherein at least some of the diffraction features have a trapezoidal cross-section.

[0419] Example 27: The optical device according to any of the above embodiments, wherein the waveguide is contained within an eyepiece for a head-mounted display.

[0420] Example 28: The optical device according to any of the above embodiments, wherein the waveguide is included in a stack of waveguides within an eyepiece for a head-mounted display.

[0421] Example 29: The optical device according to Example 27 or 28, wherein the eyepiece is transparent in order to provide the user with a view of the environment in front of the user and the head-mounted display.

[0422] Example 30: The optical device according to any of Examples 27-29, wherein the eyepiece is configured to receive light from an image projector, direct at least a portion of the light towards the user's eye, and direct image content towards the user's eye.

[0423] Example 31: The optical device according to any of Examples 27-30, wherein the eyepiece is mounted on a frame and configured to be worn on the user's head.

[0424] Example 32: An optical device according to any of the above examples, wherein the plurality of diffraction features are contained within an internally coupled optical element, which is arranged to receive light from an image source and couple the light into the substrate, in such a way that it is guided therein.

[0425] Example 33: The optical device according to any of the above embodiments, wherein the plurality of diffraction features are contained within an external coupling optical element that receives light from an image source, which is induced within the substrate, and is arranged to couple the light out of the substrate to the eyes of a user wearing the head-mounted display.

[0426] Example 34: The optical device according to any of Examples 27-33, wherein the plurality of diffraction features comprises first, second, and third diffraction features, the second diffraction feature being positioned between the first and third diffraction features.

[0427] Example 35: The optical device according to Example 35, wherein the height of the third diffraction feature is greater than the height of the second diffraction feature, and the height of the second diffraction feature is greater than the height of the first diffraction feature.

[0428] Example 36: The optical device according to Example 34 or 35, further comprising a projector positioned relative to a substrate and directing light into the substrate, wherein the projector is positioned closer to the first diffraction feature than to the second diffraction feature.

[0429] Example 37: An optical device according to any of the above examples, wherein the height of the diffraction feature gradually increases with lateral position.

[0430] Example 38: The optical device according to Example 37, further comprising a projector positioned relative to a substrate and directing light into the substrate, wherein the projector is positioned closer to the diffraction feature at a lower height than the diffraction feature at a higher height.

[0431] Example 39: An optical device according to any one of Examples 34-38, wherein the thickness of the layer of the material over the third diffraction feature is greater than the thickness of the layer of the material over the second diffraction feature, and the thickness of the layer of the material over the second diffraction feature is greater than the thickness of the layer of the material over the first diffraction feature.

[0432] Example 40: The optical device according to Example 39, further comprising a projector positioned relative to a substrate and directing light into the substrate, wherein the projector is positioned closer to the first diffraction feature than to the second diffraction feature.

[0433] Example 41: An optical device according to any of the above examples, wherein the layer of the material has a thickness that gradually increases with lateral position.

[0434] Example 42: An optical device according to any of the above embodiments, further comprising a projector positioned on a substrate and directing light into the substrate, wherein the projector is positioned closer to the diffraction feature where the layer of the material is thinner than the diffraction feature where the layer of the material is thicker.

[0435] Example 43: The optical device according to any of the above embodiments, wherein the substrate comprises opposing first and second sides.

[0436] Example 44: The optical device according to Example 43, wherein the optical device is integrated into a head-mounted display, and the second side is positioned closer to the wearer's eyes than the first side when the head-mounted display is worn.

[0437] Example 45: The optical device according to Example 43 or 44, wherein the plurality of diffraction features are arranged on the first side of the substrate.

[0438] Example 46: The optical device according to any one of Examples 43-45, further comprising a plurality of additional diffraction features formed in or on the substrate on a second opposing side of the substrate.

[0439] Example 47: The optical device according to Example 46, wherein the additional diffraction features are separated by space, and the optical device further comprises layers of additional material across the additional diffraction features.

[0440] Example 48: The optical device according to any of the above examples, wherein the 2D diffraction grating comprises a blazed grating.

[0441] Example 49: An optical device according to any of the above examples, wherein the multiple diffraction features are asymmetrical to provide a blazed grating.

[0442] Example 50: An optical device according to any of the above examples, having a material on which multiple diffraction features are asymmetrically deposited to provide a blazed lattice.

[0443] Example 51: The optical device according to any of the above embodiments, wherein the substrate includes first and second sides, and only the first side of the substrate includes a diffraction grating.

[0444] Example 52: The 2D array is an optical device according to any of the above examples, comprising a square array.

[0445] Example 53: The diffraction feature is formed within the substrate, and the optical device is as described in any of the above examples.

[0446] Example 54: The diffraction feature is formed on the substrate, and the optical device is as described in any of the above examples.

[0447] Example 55: The optical device according to any of the above examples, wherein the diffraction feature is made of a material different from the substrate.

[0448] Example 56: The optical device according to any of the above examples, wherein the diffraction feature is made of a resist.

[0449] Example 57: The optical device according to any of the above examples, wherein the diffraction feature is made of a photoresist.

[0450] Example 58: The optical device according to any of the above examples, wherein the diffraction feature is made of a material having a refractive index less than that of the substrate.

[0451] Example 59: The optical device according to any of the above examples, wherein at least a portion of the etching mask remains on the diffraction features.

[0452] Example 60: An optical device according to any of the above examples, wherein the plurality of diffraction features are contained within an internally coupled optical element, which is arranged to receive light from an image source and couple the light into the substrate, in such a way that it is guided therein.

[0453] Example 61: An optical device according to any of the above examples, wherein the plurality of diffraction features are contained within a light-dispersive optical element that receives light from an image source, which is induced within the substrate, and is positioned to direct the light to an external coupling optical element so as to couple out of the substrate.

[0454] Example 62: An optical device according to any of the above examples, wherein the plurality of diffraction features are contained within an optically dispersed optical element, which receives light from an image source, diffuses the light outward in the waveguide, and is arranged to increase the beam size or eyebox size, thereby inducing the diffraction features within the substrate.

[0455] Example 63: An optical device according to any of the above examples, wherein the plurality of diffraction features are contained within an externally coupled optical element that receives light from an image source and is arranged to couple the light out of the substrate, the diffraction features being induced within the substrate.

[0456] Example 64: An optical device according to any of the above examples, wherein the plurality of diffraction features are contained within a combined optical dispersion / external coupling optical element, which is arranged to receive light from an image source, diffuse the light outward in at least two directions, and couple the light outward from the substrate, thereby inducing the diffraction features within the substrate.

[0457] Example 65: An optical device according to any of the above examples, wherein the plurality of diffraction features are contained within a combined pupil expander-extractor arranged to receive light from an image source, diffuse the light outward, and couple the light outward from the substrate, thereby inducing the diffraction features within the substrate.

[0458] Example 66: The method according to any of the above embodiments, wherein the 2D diffraction grating comprises a blazed diffraction grating configured to preferentially direct light in at least two directions.

[0459] Example 67: The method according to any of the above examples, wherein the 2D diffraction grating comprises a blazed diffraction grating blazed in two directions. (Example IV)

[0460] Example 1: A head-mounted display, A frame configured to be worn on the user's head, Mounted on the frame, the eyepiece is transparent to provide the user with a view of the environment in front of the user and the head-mounted display, and is configured to receive light from an image projector and direct at least a portion of the light to the user's eye and direct image content to the user's eye, and comprises a waveguide constituting a substrate made of a material having a refractive index greater than 2.0 that is transparent to visible light, Multiple diffraction features formed in or on the substrate, A head-mounted display comprising the diffraction features, wherein the diffraction features are arranged in a two-dimensional (2D) array to form a 2D diffraction grating.

[0461] Example 2: A head-mounted display comprising a frame and a display configured to be worn on the user's head. Mounted on the frame, the eyepiece is transparent to provide the user with a view of the environment in front of the user and the head-mounted display, and is configured to receive light from an image projector and direct at least a portion of the light to the user's eye and direct image content to the user's eye, and comprises a waveguide constituting a substrate made of a material having a refractive index greater than 2.0 that is transparent to visible light, Multiple diffraction features formed in or on the substrate, A head-mounted display comprising, wherein the diffraction features are blazed.

[0462] Example 3: A head-mounted display, A frame configured to be worn on the user's head, Mounted on the frame, the eyepiece is transparent to provide the user with a view of the environment in front of the user and the head-mounted display, and is configured to receive light from an image projector and direct at least a portion of the light to the user's eye and direct image content to the user's eye, and comprises a waveguide constituting a substrate made of a material having a refractive index greater than 2.0 that is transparent to visible light, Multiple diffraction features formed in or on the substrate, A head-mounted display comprising multiple diffraction features, the multiple diffraction features being induced within the substrate, receiving light from an image source, diffusing the light outward in at least two directions, and being arranged to couple the light outward from the substrate, within a combined optical dispersion / external coupling optical element.

[0463] Example 4: A head-mounted display, A frame configured to be worn on the user's head, Mounted on the frame, the eyepiece is transparent to provide the user with a view of the environment in front of the user and the head-mounted display, and is configured to receive light from an image projector and direct at least a portion of the light to the user's eye and direct image content to the user's eye, and comprises a waveguide constituting a substrate made of a material having a refractive index greater than 2.0 that is transparent to visible light, Multiple diffraction features formed in or on the substrate, A head-mounted display comprising a plurality of diffraction features, the plurality of which are contained within a combined pupil expander-extractor arranged to receive light from an image source, diffuse the light outward, and couple the light outward from the substrate, thereby induced within the substrate.

[0464] Example 5: A head-mounted display, A frame configured to be worn on the user's head, Mounted on the frame, the eyepiece is transparent to provide the user with a view of the environment in front of the user and the head-mounted display, and is configured to receive light from an image projector and direct at least a portion of the light to the user's eye and direct image content to the user's eye, and comprises a waveguide constituting a substrate made of a material having a refractive index greater than 2.0 that is transparent to visible light, Multiple diffraction features formed on the substrate, A layer is disposed between the diffraction feature and the substrate, A head-mounted display equipped with the following features.

[0465] Example 6: The head-mounted display described in Example 5, wherein the layer is made of a material different from the substrate material.

[0466] Example 7: The head-mounted display according to Example 5 or 6, wherein the layer comprises an adhesion promoter layer.

[0467] Example 8: A head-mounted display according to any one of Examples 5-7, wherein the layer is made of a high refractive index material having a refractive index greater than 1.79, and the high refractive index material is made of a different material from the substrate material.

[0468] Example 9: A head-mounted display according to any one of Examples 5-7, wherein the layer is made of a high refractive index material having a refractive index greater than 2.0, and the high refractive index material is made of a different material from the substrate material.

[0469] Example 10: The method according to any one of Examples 5-9, wherein the layer consists of a dielectric layer.

[0470] Example 11: The head-mounted display according to Example 5, wherein the layer consists of titanium dioxide, zirconium dioxide, silicon nitride, or silicon carbide.

[0471] Example 12: The head-mounted display according to Example 5, wherein the layer is made of titanium dioxide.

[0472] Example 13: The head-mounted display according to Example 5, wherein the layer is made of zirconium dioxide.

[0473] Example 14: The head-mounted display according to Example 5, wherein the layer is made of silicon nitride.

[0474] Example 15: The head-mounted display according to Example 5, wherein the layer contains silicon carbide.

[0475] Example 16: A head-mounted display according to any of Examples 5-15, wherein the layer reduces reflection from the substrate.

[0476] Example 17: A head-mounted display, A frame configured to be worn on the user's head, Mounted on the frame, the eyepiece is transparent to provide the user with a view of the environment in front of the user and the head-mounted display, and is configured to receive light from an image projector and direct at least a portion of the light to the user's eye and direct image content to the user's eye, and comprises a waveguide constituting a substrate made of a material having a refractive index greater than 2.0 that is transparent to visible light, Multiple diffraction features formed on the substrate, A head-mounted display comprising a diffraction feature comprising a plurality of layers, namely a first layer and a second layer extending over the first layer.

[0477] Example 18: The head-mounted display according to Example 17, wherein the first layer is made of a dielectric material.

[0478] Example 19: The head-mounted display according to Example 17 or 18, wherein the second layer is made of a dielectric material.

[0479] Example 20: A head-mounted display according to any one of Examples 17-19, wherein the first layer has a refractive index between that of the substrate and that of the second layer.

[0480] Example 21: A head-mounted display according to any of Examples 17-20, further comprising a third layer extending over a second layer.

[0481] Example 22: The head-mounted display according to Example 21, wherein the third layer is made of a dielectric material.

[0482] Example 23: A head-mounted display according to any one of Examples 21-22, wherein the second layer has a refractive index between that of the second layer and that of the third layer.

[0483] Example 24: A head-mounted display according to any of Examples 17-23, wherein the first layer is made of titanium dioxide.

[0484] Example 25: A head-mounted display according to any of Examples 17-24, wherein the second layer is made of silicon nitride.

[0485] Example 26: A head-mounted display according to any of Examples 21-25, wherein the third layer is made of silicon dioxide.

[0486] Example 27: A head-mounted display according to any of Examples 17-26, wherein the first and second layers reduce reflection from the substrate.

[0487] Example 28: A head-mounted display according to any of Examples 17-27, wherein the first layer, the second layer, and the third layer reduce reflection from the substrate.

[0488] Example 29: A head-mounted display, A frame configured to be worn on the user's head, Mounted on the frame, the eyepiece is transparent to provide the user with a view of the environment in front of the user and the head-mounted display, and is configured to receive light from an image projector and direct at least a portion of the light to the user's eye and direct image content to the user's eye, and comprises a waveguide constituting a substrate made of a material having a refractive index greater than 2.0 that is transparent to visible light, Multiple diffraction features formed on or within the substrate, A layer comprising at least one layer spanning the plurality of diffraction features, A head-mounted display equipped with the following features.

[0489] Example 30: The head-mounted display according to Example 29, wherein at least one layer is made of a material different from the substrate material.

[0490] Example 31: The head-mounted display according to Example 29 or 30, wherein at least one layer is made of a dielectric material.

[0491] Example 32: A head-mounted display according to any one of Examples 29-31, wherein the at least one layer consists of at least one layer of titanium dioxide.

[0492] Example 33: A head-mounted display according to any one of Examples 29-32, wherein the at least one layer consists of at least one layer of silicon dioxide.

[0493] Example 34: The head-mounted display according to any one of Examples 29-33, wherein the at least one layer consists of at least one layer of magnesium fluoride.

[0494] Example 35: A head-mounted display according to any one of Examples 29-34, wherein the at least one layer consists of multiple layers of titanium dioxide.

[0495] Example 36: A head-mounted display according to any one of Examples 29-35, wherein the at least one layer consists of multiple layers of silicon dioxide.

[0496] Example 37: A head-mounted display according to any one of Examples 29-36, wherein the at least one layer consists of multiple layers of magnesium fluoride.

[0497] Example 38: A head-mounted display according to any of Examples 29-37, wherein at least one layer consists of alternating layers of material.

[0498] Example 39: A head-mounted display according to any one of Examples 29-38, wherein the at least one layer consists of repeating layers of material.

[0499] Example 40: A head-mounted display according to any one of Examples 29-39, wherein the at least one layer reduces reflection from the substrate.

[0500] Example 41: A head-mounted display, A frame configured to be worn on the user's head, Mounted on the frame, the eyepiece is transparent to provide the user with a view of the environment in front of the user and the head-mounted display, and is configured to receive light from an image projector and direct at least a portion of the light to the user's eye and direct image content to the user's eye, and comprises a waveguide constituting a substrate made of a material having a refractive index greater than 2.0 that is transparent to visible light, A diffractive optical element formed on or within the substrate, One or more anti-reflective layers across the diffractive optical elements, A head-mounted display equipped with the following features.

[0501] Example 42: The head-mounted display according to Example 41, wherein one or more anti-reflection layers are made of a material having a refractive index less than that of the waveguide material.

[0502] Example 43: The head-mounted display according to Example 41, wherein one or more anti-reflective layers are made of a material having a refractive index of 1.2 to 1.7.

[0503] Example 44: The head-mounted display according to Example 41, wherein one or more anti-reflective layers consist of magnesium fluoride.

[0504] Example 45: A head-mounted display according to Example 41 or 44, wherein one or more anti-reflective layers are made of silicon dioxide.

[0505] Example 46: A head-mounted display according to any one of Examples 41-43, wherein one or more anti-reflective layers consist of a resist.

[0506] Example 47: A head-mounted display according to any of Examples 41-46, wherein multiple anti-reflective layers are arranged across the diffractive optical elements.

[0507] Example 48: The head-mounted display according to Example 47, wherein one of the anti-reflective layers further away from the substrate has a lower refractive index than one of the anti-reflective layers closer to the substrate.

[0508] Example 49: The head-mounted display according to Example 47, wherein the anti-reflection layer furthest from the substrate has a lower refractive index than the anti-reflection layer closest to the waveguide, and one or more anti-reflection layers between the anti-reflection layer furthest from the substrate and the anti-reflection layer closest to the substrate have a refractive index between that of the anti-reflection layer furthest from the substrate and that of the anti-reflection layer closest to the substrate.

[0509] Example 50: A head-mounted display according to any of Examples 41-49, wherein one or more anti-reflective layers are positioned on one side of the diffraction grating more than on the other.

[0510] Example 51: A head-mounted display according to any of Examples 41-49, wherein the sidewalls and grooves of the diffractive optical element consist of one or more anti-reflective layers of a very small amount of material.

[0511] Example 52: A head-mounted display according to any of Examples 41-49, wherein the anti-reflective layer material is deposited on the surface of the substrate and on the upper surface of multiple diffraction features of the diffractive optical element parallel to the surface of the trench of the diffractive optical element, and the sidewalls of the diffractive optical element consist of a very small amount of the anti-reflective layer material.

[0512] Example 53: A head-mounted display according to any of Examples 41-49, wherein the anti-reflective layer material is deposited on both the horizontal and vertical exposed surfaces of multiple features of the optical element.

[0513] Example 54: A head-mounted display according to any of Examples 41-53, wherein the anti-reflection layer on the diffractive optical element is planarized.

[0514] Example 55: A head-mounted display according to any of Examples 41-54, further comprising a structural stability-providing layer disposed over one or more anti-reflective layers to increase structural stability.

[0515] Example 56: The head-mounted display according to Example 55, wherein the structural stability-providing layer is made of glass.

[0516] Example 57: The head-mounted display according to Example 55, wherein the structural stability-providing layer is made of glass having an anti-reflective coating thereon.

[0517] Example 58: The head-mounted display according to Example 57, wherein the anti-reflective coating on the glass consists of alternating layers.

[0518] Example 59: The head-mounted display according to Example 58, wherein the anti-reflective coating on the glass consists of alternating layers of TiO2 and SiO2.

[0519] Example 60: A head-mounted display according to any of Examples 41-59, further comprising an additional layer between the anti-reflective layer and the diffraction features of the diffractive optical element.

[0520] Example 61: A head-mounted display, A frame configured to be worn on the user's head, Mounted on the frame, the eyepiece is transparent to provide the user with a view of the environment in front of the user and the head-mounted display, and is configured to receive light from an image projector and direct at least a portion of the light to the user's eye and direct image content to the user's eye, and comprises a waveguide constituting a substrate made of a material having a refractive index greater than 2.0 that is transparent to visible light, A diffractive optical element formed on or within the substrate, An anti-reflective structure comprising nanostructures arranged across diffractive optical elements, configured to reduce reflection, A head-mounted display equipped with the following features.

[0521] Example 62: The head-mounted display according to Example 61, wherein the nanostructure is directly located on the diffractive optical element.

[0522] Example 63: A head-mounted display according to Example 61, wherein the nanostructure is formed within a coating and arranged across diffractive optical elements.

[0523] Example 64: A head-mounted display according to Example 63, wherein the coating has a lower refractive index than that of the substrate.

[0524] Example 65: A head-mounted display according to Example 63 or 64, wherein the coating consists of a photoresist.

[0525] Example 66: A head-mounted display, A frame configured to be worn on the user's head, Mounted on the frame, the eyepiece is transparent to provide the user with a view of the environment in front of the user and the head-mounted display, and is configured to receive light from an image projector and direct at least a portion of the light to the user's eye and direct image content to the user's eye, and comprises a waveguide constituting a substrate made of a material having a refractive index greater than 2.0 that is transparent to visible light, A diffractive optical element formed on or within the substrate, One or more reflective gratings are positioned at the edge of the substrate and receive light propagating to the edge of the substrate by total internal reflection within the substrate, A head-mounted display equipped with the following features.

[0526] Example 67: The head-mounted display according to Example 66, wherein one or more reflective grids are configured to redirect light away from the edges and towards the rear.

[0527] Example 68: A head-mounted display according to Example 66 or 67, wherein one or more reflective gratings are configured to direct light back toward an external coupling optical element configured to couple the light out of the substrate toward the user.

[0528] Example 69: A head-mounted display according to Example 68, wherein the external coupling optical element comprises a diffractive optical element having a certain pitch, and one or more reflective gratings have a pitch that is about half the pitch of the external coupling optical element.

[0529] Example 70: A head-mounted display according to any of Examples 66-69, wherein one or more reflective grids are metallized.

[0530] Example 71: A head-mounted display, A frame configured to be worn on the user's head, Mounted on the frame, the eyepiece is transparent to provide the user with a view of the environment in front of the user and the head-mounted display, and is configured to receive light from an image projector and direct at least a portion of the light to the user's eye and direct image content to the user's eye, and comprises a waveguide constituting a substrate made of a material having a refractive index greater than 2.0 that is transparent to visible light, A diffractive optical element formed on or within the substrate, A light extraction feature positioned at the edge of the substrate, which receives light propagating to the edge of the substrate through total internal reflection within the substrate, A head-mounted display equipped with the following features.

[0531] Example 72: The head-mounted display according to Example 71, wherein the light extraction feature is configured to extract light outwards from the edges.

[0532] Example 73: A head-mounted display according to Example 71 or 72, wherein the light extraction feature is a diffraction feature.

[0533] Example 74: A head-mounted display according to any one of Examples 71-73, further comprising an absorbing element positioned around the edge and receiving light extracted by the light extraction feature.

[0534] Example 75: The head-mounted display according to Example 74, wherein the absorbent element comprises a cuff, collar, cup, or sleeve.

[0535] Example 76: The head-mounted display according to Example 74 or 75, wherein the absorbing element is made of carbon black.

[0536] Example 77: A head-mounted display according to any one of Examples 71-76, further comprising an absorption coating on the light extraction feature.

[0537] Example 78: A head-mounted display, A frame configured to be worn on the user's head, Mounted on the frame, the eyepiece is transparent to provide the user with a view of the environment in front of the user and the head-mounted display, and is configured to receive light from an image projector and direct at least a portion of the light to the user's eye and direct image content to the user's eye, and comprises a waveguide constituting a substrate made of a material having a refractive index greater than 2.0 that is transparent to visible light, A diffractive optical element formed on or within the substrate, A head-mounted display comprising at least one structural support layer, with the substrate, for providing increased structural strength.

[0538] Example 79: The head-mounted display according to Example 78, wherein at least one structural support layer is made of a material having a refractive index of 1.7 or less.

[0539] Example 80: The head-mounted display according to Example 78 or 79, wherein at least one structural support layer is made of glass.

[0540] Example 81: The head-mounted display according to Example 80, wherein at least one structural support layer is made of glass having an anti-reflective coating thereon.

[0541] Example 82: A head-mounted display according to any one of Examples 78-81, wherein at least the structural support layer is directly adjacent to the substrate.

[0542] Example 83: A head-mounted display according to any one of Examples 78-82, wherein at least one structural support layer fills the spaces between multiple diffraction features of a diffractive optical element.

[0543] Example 84: A head-mounted display according to any one of Examples 78-82, further comprising air between the at least one structural support layer and the substrate.

[0544] Example 85: A head-mounted display according to any one of Examples 78-82 and 84, further comprising air between the at least one structural support layer and the plurality of diffraction features.

[0545] Example 86: A head-mounted display according to any one of Examples 78-84 and 84 and 85, further comprising a spacer between the at least one structural support layer and the substrate, thereby providing a gap between the at least one structural support layer and the substrate.

[0546] Example 87: A head-mounted display according to any of Examples 78-82 and 83-86, wherein the void is provided by a polymer layer.

[0547] Example 88: A head-mounted display according to any one of Examples 78-86, wherein at least one structural support layer provides scratch-resistant functionality.

[0548] Example 89: A head-mounted display according to any one of Examples 78-88, wherein at least one structural support layer comprises a low refractive index coating.

[0549] Example 90: A head-mounted display according to any one of Examples 78-89, wherein at least one structural support layer is made of anti-reflective glass.

[0550] Example 91: A head-mounted display according to any of Examples 78-90, wherein at least one structural support layer is located on one side of the substrate.

[0551] Example 92: The head-mounted display according to any one of Examples 78-91, wherein the structural support layer comprises at least two structural support layers.

[0552] Example 93: The head-mounted display according to Example 92, wherein the at least two structural support layers are arranged on opposite sides of the substrate.

[0553] Example 94: A head-mounted display, A frame configured to be worn on the user's head, Mounted on the frame, the eyepiece is transparent to provide the user with a view of the environment in front of the user and the head-mounted display, and is configured to receive light from an image projector and direct at least a portion of the light to the user's eye and direct image content to the user's eye, and comprises a waveguide constituting a substrate made of a material having a refractive index greater than 2.0 that is transparent to visible light, A diffractive optical element formed on or within the substrate, Optical components extending to the diffractive optical element, A head-mounted display equipped with the following features.

[0554] Example 95: The head-mounted display according to Example 94, wherein the optical component is in contact with the diffraction feature.

[0555] Example 96: The head-mounted display according to Example 94, further comprising a planarization layer between the optical component and the diffraction feature.

[0556] Example 97: The head-mounted display according to Example 94, further comprising a structural stability-providing layer between the optical component and the substrate.

[0557] Example 98: The head-mounted display according to Example 94, further comprising a planarization layer between the optical component and the substrate.

[0558] Example 99: A head-mounted display according to any of Examples 94-98, wherein the optical component is at least 1 centimeter (cm) in spatial range.

[0559] Example 100: A head-mounted display according to any of Examples 94-98, wherein the optical component is at least several centimeters within a spatial range.

[0560] Example 101: The head-mounted display according to any one of Examples 94-100, wherein the optical component comprises a refractive optical component.

[0561] Example 102: The head-mounted display according to any one of Examples 94-100, wherein the optical component comprises a diffractive optical component.

[0562] Example 103: The optical component comprises a lens, and is a head-mounted display according to any of Examples 94-102.

[0563] Example 104: The head-mounted display according to Example 103, wherein the lens is at least 1 centimeter (cm) in spatial range.

[0564] Example 105: The head-mounted display according to Example 103, wherein the lens is at least several centimeters in size within the spatial range.

[0565] Example 106: The head-mounted display according to any one of Examples 103-105, wherein the lens comprises a convex lens.

[0566] Example 107: The head-mounted display according to any one of Examples 103-105, wherein the lens comprises a concave lens.

[0567] Example 108: The head-mounted display according to any one of Examples 103-107, wherein the lens comprises a Fresnel lens.

[0568] Example 109: A head-mounted display, A frame configured to be worn on the user's head, Mounted on the frame, the eyepiece is transparent to provide the user with a view of the environment in front of the user and the head-mounted display, and is configured to receive light from an image projector and direct at least a portion of the light to the user's eye and direct image content to the user's eye, and comprises a waveguide constituting a substrate made of a material having a refractive index greater than 2.0 that is transparent to visible light, Multiple diffraction features formed in or on the substrate, A head-mounted display comprising a diffraction feature height, diffraction feature width, diffraction feature shape, spacing between diffraction features, sidewall inclination on the diffraction features, or any combination thereof, which varies across the substrate.

[0569] Example 110: A head-mounted display according to Example 109, wherein the height of the diffraction features, the width of the diffraction features, the shape of the diffraction features, the spacing between the diffraction features, the inclination of the sidewalls on the diffraction features, or any combination thereof, gradually changes with distance across the substrate.

[0570] Example 111: A head-mounted display according to Example 109 or 110, wherein the height of the diffraction feature varies with distance across the substrate.

[0571] Example 112: A head-mounted display according to any of Examples 109-111, wherein the height of the diffraction feature gradually changes with distance across the substrate.

[0572] Example 113: A head-mounted display according to any of Examples 109-112, wherein the width of the diffraction feature varies with distance across the substrate.

[0573] Example 114: A head-mounted display according to any of Examples 109-113, wherein the width of the diffraction feature gradually changes with distance across the substrate.

[0574] Example 115: A head-mounted display according to any of Examples 109-114, wherein the shape of the diffraction features varies with distance across the substrate.

[0575] Example 116: A head-mounted display according to any of Examples 109-115, wherein the shape of the diffraction features gradually changes with distance across the substrate.

[0576] Example 117: A head-mounted display according to any of Examples 109-116, wherein the spacing between diffraction features varies with distance across the substrate.

[0577] Example 118: A head-mounted display according to any of Examples 109-117, wherein the spacing between diffraction features gradually changes with distance across the substrate.

[0578] Example 119: A head-mounted display according to any of Examples 109-118, wherein the inclination of the sidewalls on the diffraction features varies with distance across the substrate.

[0579] Example 120: A head-mounted display according to any of Examples 109-119, wherein the inclination of the sidewalls on the diffraction features gradually changes with distance across the substrate.

[0580] Example 121: A head-mounted display according to any of Examples 109-120, wherein the inclination of the sidewalls on the diffraction features gradually changes with distance across the substrate.

[0581] Example 122: A head-mounted display according to Example 109, wherein the height of the diffraction features, the width of the diffraction features, the shape of the diffraction features, the spacing between the diffraction features, the inclination of the sidewalls on the diffraction features, or any combination thereof, gradually varies in one direction with distance across the substrate, and then gradually varies in the opposite direction.

[0582] Example 123: A head-mounted display, A frame configured to be worn on the user's head, Mounted on the frame, the eyepiece is transparent to provide the user with a view of the environment in front of the user and the head-mounted display, and is configured to receive light from an image projector and direct at least a portion of the light to the user's eye and direct image content to the user's eye, and comprises a waveguide constituting a substrate made of a material having a refractive index greater than 2.0 that is transparent to visible light, Multiple diffraction features formed in or on the substrate, A head-mounted display comprising a circuit board which is colored.

[0583] Example 124: A head-mounted display, A frame configured to be worn on the user's head, Mounted on the frame, the eyepiece is transparent to provide the user with a view of the environment in front of the user and the head-mounted display, and is configured to receive light from an image projector and direct at least a portion of the light to the user's eye and direct image content to the user's eye, and comprises a waveguide constituting a substrate made of a material having a refractive index greater than 2.0 that is transparent to visible light, Multiple diffraction features formed in or on the substrate, A head-mounted display comprising a diffraction feature with a height of 10-50 nm.

[0584] Example 125: A head-mounted display, A frame configured to be worn on the user's head, Mounted on the frame, the eyepiece is transparent to provide the user with a view of the environment in front of the user and the head-mounted display, and is configured to receive light from an image projector and direct at least a portion of the light to the user's eye and direct image content to the user's eye, and comprises a waveguide constituting a substrate made of a material having a refractive index greater than 2.0 that is transparent to visible light, Multiple diffraction features formed on the substrate, A head-mounted display comprising a diffraction feature wherein the diffraction feature is made of a material having a refractive index of at least 1.8, and the material is different from the material of the substrate.

[0585] Example 126: A head-mounted display, A frame configured to be worn on the user's head, Mounted on the frame, the eyepiece is transparent to provide the user with a view of the environment in front of the user and the head-mounted display, and is configured to receive light from an image projector and direct at least a portion of the light to the user's eye and direct image content to the user's eye, and comprises a waveguide constituting a substrate made of a material having a refractive index greater than 2.0 that is transparent to visible light, Multiple diffraction features formed in or on the substrate, A planarized layer over the diffraction features, A head-mounted display equipped with the following features.

[0586] Example 127: The head-mounted display according to Example 126, wherein the planarized layer has a refractive index of less than 1.6.

[0587] Example 128: A head-mounted display, A frame configured to be worn on the user's head, Mounted on the frame, the eyepiece is transparent to provide the user with a view of the environment in front of the user and the head-mounted display, and is configured to receive light from an image projector and direct at least a portion of the light to the user's eye and direct image content to the user's eye, and comprises a waveguide constituting a substrate made of a material having a refractive index greater than 2.0 that is transparent to visible light, A diffractive optical element formed in or on the substrate, An anti-reflective coating on the side opposite to the diffractive optical element of the substrate, A head-mounted display equipped with the following features.

[0588] Example 129: A head-mounted display, A frame configured to be worn on the user's head, Mounted on the frame, the eyepiece is transparent to provide the user with a view of the environment in front of the user and the head-mounted display, and is configured to receive light from an image projector and direct at least a portion of the light to the user's eye and direct image content to the user's eye, and comprises a waveguide constituting a substrate made of a material having a refractive index greater than 2.0 that is transparent to visible light, Multiple diffraction features formed in or on the substrate, A head-mounted display comprising, wherein the first and second diffractive optical elements are positioned on the first and second opposing surfaces of the waveguide.

[0589] Example 130: The method according to Example 129, wherein multiple diffraction features of the first diffractive optical element are offset from multiple diffraction features of the second diffractive optical element.

[0590] Example 131: A head-mounted display according to any of the above examples, wherein the diffractive optical element or diffraction grating comprises a blazed grating.

[0591] Example 132: A head-mounted display according to any of the above examples, wherein multiple diffraction features form a diffraction grating, and the diffraction grating comprises a blazed grating.

[0592] Example 133: A head-mounted display according to any of the above examples, wherein multiple diffraction features are asymmetrical to provide a blazed grating.

[0593] Example 134: A head-mounted display according to any of the above examples, having a material on which multiple diffractions are asymmetrically deposited to provide a blazed grating.

[0594] Example 135: A head-mounted display according to any of the above embodiments, wherein the substrate includes first and second sides, and only the first side of the substrate includes a diffraction grating.

[0595] Example 136: A head-mounted display according to any of the above examples, wherein the diffraction features are arranged within a 1D array.

[0596] Example 137: A head-mounted display according to any of the above examples, wherein the diffraction features are arranged in a 2D array.

[0597] Example 138: The 2D array is a head-mounted display according to Example 137, comprising a square array.

[0598] Example 139: A head-mounted display according to any of the above examples, wherein the diffractive optical element or diffraction grating comprises a 1D array.

[0599] Example 140: A head-mounted display according to any of the above examples, wherein the diffractive optical element or diffraction grating comprises a 2D array.

[0600] Example 141: The 2D array is a head-mounted display according to Example 140, comprising a square array.

[0601] Example 142: The head-mounted display according to any of the above examples, wherein the substrate material contains lithium niobate.

[0602] Example 143: The substrate material is silicon carbide, and the head-mounted display is as described in any of the above examples.

[0603] Example 144: The head-mounted display according to any of the above examples, wherein the substrate material has a refractive index of at least 2.1.

[0604] Example 145: The head-mounted display according to any of the above examples, wherein the substrate material has a refractive index of at least 2.2.

[0605] Example 146: The substrate material has a refractive index of at least 2.3, the head-mounted display according to any of the above examples.

[0606] Example 147: The diffractive feature is made of a material different from the substrate, the head-mounted display according to any of the above examples.

[0607] Example 148: The diffractive material has a refractive index of less than 1.8, the head-mounted display according to any of the above examples.

[0608] Example 149: A head-mounted display according to any of the above embodiments, wherein the diffraction features are separated by space, and the space comprises an exposure region of the substrate material.

[0609] Example 150: A head-mounted display according to any of the above examples, wherein the diffraction features are separated by space, and the space between the diffraction features is not covered by a layer of the material.

[0610] Example 151: A head-mounted display according to any of the above embodiments, wherein the diffraction features are separated by space, and the space between the diffraction features comprises an exposure region of the substrate material.

[0611] Example 152: A head-mounted display according to any of the above examples, wherein at least some of the diffraction features have inclined sidewalls.

[0612] Example 153: A head-mounted display according to any of the above examples, wherein at least some of the diffraction features have a trapezoidal cross-section.

[0613] Example 154: A head-mounted display according to any of the above examples, wherein the waveguide is included in a stack of waveguides within an eyepiece for a head-mounted display.

[0614] Example 155: A head-mounted display according to any of the above embodiments, wherein the plurality of diffraction features are contained within an internally coupled optical element, which is arranged to receive light from an image source and couple the light into the substrate, in such a manner that it is guided therein.

[0615] Example 156: A head-mounted display according to any of the above embodiments, wherein the plurality of diffraction features are induced within the substrate, and are contained within an external coupling optical element that receives light from an image source and couples the light out of the substrate to the eyes of a user wearing the head-mounted display.

[0616] Example 157: The head-mounted display according to any of the above embodiments, wherein the substrate comprises opposing first and second sides.

[0617] Example 158: The head-mounted display according to Example 157, wherein the second side is positioned closer to the wearer's eyes than the first side when the head-mounted display is attached.

[0618] Example 159: The head-mounted display according to Example 157 or 158, wherein the plurality of diffraction features are arranged on the first side of the substrate.

[0619] Example 160: A head-mounted display according to any one of Examples 157-159, further comprising a plurality of additional diffraction features formed in or on the substrate on a second opposing side of the substrate.

[0620] Example 161: A head-mounted display according to any of the above embodiments, wherein the substrate includes first and second sides, and only the first side of the substrate includes a diffraction grating.

[0621] Example 162: A head-mounted display according to any of the above examples, wherein the diffraction features are formed within the substrate.

[0622] Example 163: A head-mounted display according to any of the above examples, wherein the diffraction features are formed on the substrate.

[0623] Example 164: The diffractive feature is made of a material different from the substrate, the head-mounted display according to any of the above examples.

[0624] Example 165: The diffractive feature is made of a polymer, and the head-mounted display is as described in any of the above examples.

[0625] Example 166: The diffractive feature is made of a resist, the head-mounted display according to any of the above examples.

[0626] Example 167: The diffractive feature is made of photoresist, and the head-mounted display is as described in any of the above examples.

[0627] Example 168: A head-mounted display according to any of the above examples, wherein the diffraction feature is made of a material having a refractive index less than that of the substrate.

[0628] Example 169: A head-mounted display according to any of the above embodiments, wherein the plurality of diffraction features are contained within an internally coupled optical element, which is arranged to receive light from an image source and couple the light into the substrate, in such a way that it is guided therein.

[0629] Example 170: A head-mounted display according to any of the above examples, wherein the plurality of diffraction features are contained within a light-dispersive optical element that receives light from an image source, which is induced within the substrate, and is positioned to direct the light to an external coupling optical element so as to couple out of the substrate.

[0630] Example 171: A head-mounted display according to any of the above embodiments, wherein the plurality of diffraction features are contained within an optically dispersed optical element, which is arranged to receive light from an image source, diffuse the light outward in the waveguide, and increase the beam size or eyebox size, and is induced within the substrate.

[0631] Example 172: A head-mounted display according to any of the above examples, wherein the plurality of diffraction features are induced within the substrate and contained within an external coupling optical element that receives light from an image source and is arranged to couple the light out of the substrate.

[0632] Example 173: A head-mounted display according to any of the above examples, wherein the plurality of diffraction features are contained within a combined optical dispersion / external coupling optical element arranged to receive light from an image source, diffuse the light outward in at least two directions, and couple the light outward from the substrate, which is induced within the substrate.

[0633] Example 174: A head-mounted display according to any of the above examples, wherein the plurality of diffraction features are contained within a combined pupil expander-extractor arranged to receive light from an image source, diffuse the light outward, and couple the light outward from the substrate, which is induced within the substrate.

[0634] Example 175: A head-mounted display according to any of the above embodiments, comprising a blazed diffraction grating, wherein the diffraction feature or diffraction grating is configured to preferentially direct light in at least two directions.

[0635] Example 176: A head-mounted display according to any of the above embodiments, wherein the diffraction feature or diffraction grating comprises a blazed diffraction grating blazed in two directions.

[0636] Example 177: A head-mounted display, A frame configured to be worn on the user's head, Mounted on the frame, the eyepiece is transparent to provide the user with a view of the environment in front of the user and the head-mounted display, and is configured to receive light from an image projector and direct at least a portion of the light to the user's eye and direct image content to the user's eye, and comprises a waveguide constituting a substrate made of a material having a refractive index greater than 2.0 that is transparent to visible light, Multiple diffraction features formed on the substrate, A head-mounted display comprising a diffractive feature, the diffractive feature of which is made of polymer.

[0637] Example 178: The head-mounted display according to any of the above examples, wherein the substrate material contains lithium niobate.

[0638] Example 179: The head-mounted display according to any of the above examples, wherein the substrate material contains silicon carbide.

[0639] Example 180: The substrate material has a refractive index of at least 2.1, the head-mounted display according to any of the above examples.

[0640] Example 181: The head-mounted display according to any of the above examples, wherein the substrate material has a refractive index of at least 2.2.

[0641] Example 182: The head-mounted display according to any of the above examples, wherein the substrate material has a refractive index of at least 2.3.

[0642] Example 183: The diffractive feature is made of a material different from the substrate, as described in any of the above examples, for a head-mounted display.

[0643] Example 184: The diffractive feature is a head-mounted display according to any of the above examples, comprising a material having a refractive index of less than 1.8.

[0644] Example 185: A head-mounted display according to any of the above examples, wherein the diffraction features are arranged within a 1D array.

[0645] Example 186: A head-mounted display according to any of the above examples, wherein the diffraction features are arranged in a 2D array.

[0646] Example 187: A head-mounted display according to any of the above examples, with diffractive features blazed.

[0647] Example 188: A head-mounted display according to any of the above examples, wherein the diffraction features are blazed in two directions. This specification also provides, for example, the following items: (Item 1) An optical device, A substrate made of a material having a refractive index greater than 2.0 that is transparent to visible light, wherein the substrate comprises a waveguide, Multiple diffraction features formed within the substrate, A layer of material arranged across the diffraction features An optical device equipped with the following features. (Item 2) The optical device according to item 1, wherein the substrate material comprises lithium niobate or silicon carbide. (Item 3) The optical device according to item 1 or 2, wherein the substrate material has a refractive index of at least 2.1. (Item 4) The optical device according to any of the above items, wherein the layer of the material has a refractive index of less than 1.8. (Item 5) The optical device according to any of the above items, wherein the layer of the material is made of photoresist. (Item 6) The optical device according to any of the above items, wherein the diffraction features are separated by space, and the space comprises an exposure region of the substrate material. (Item 7) The optical device according to any of the above items, wherein the diffraction features are separated by space, and the spaces between the diffraction features are not covered by a layer of material. (Item 8) The optical device according to any of the above items, wherein the plurality of diffraction features comprises first, second, and third diffraction features that are displaced laterally relative to each other, and the second diffraction feature is positioned between the first diffraction feature and the third diffraction feature. (Item 9) The optical device according to item 8, wherein the layers of the material have different thicknesses across each of the first, second, and third diffraction features. (Item 10) The optical device according to item 8 or 9, wherein the thickness of the layer of the material over the third diffraction feature is greater than the thickness of the layer of the material over the second diffraction feature, and the thickness of the layer of the material over the second diffraction feature is greater than the thickness of the layer of the material over the first diffraction feature. (Item 11) The optical device according to item 8, wherein the layers of the material have the same thickness across the first, second, and third diffraction features. (Item 12) The optical device according to any one of items 8-11, wherein the height of the third diffraction feature is greater than the height of the second diffraction feature, and the height of the second diffraction feature is greater than the height of the first diffraction feature. (Item 13) The thickness of the substrate is stepped, as described in any of the above items for the optical device. (Item 14) The optical device according to any of the above items, wherein the thickness of the layer of the material is stepped. (Item 15) The waveguide is an optical device according to any of the above items, contained within an eyepiece for a head-mounted display. (Item 16) The waveguide is included in a stack of waveguides within an eyepiece for a head-mounted display, as described in any of the above items. (Item 17) The optical device described in any of the above items, wherein the diffraction features are arranged within a 1D array. (Item 18) The optical device described in any of the above items, wherein the diffraction features are arranged within a 2D array. (Item 19) The optical device according to any of the above items, wherein the plurality of diffraction features are asymmetrical so as to provide a blazed grating. (Item 20) The optical device according to any of the above items, wherein the plurality of diffraction features have a material deposited asymmetrically thereon to provide a blazed lattice. (Item 21) The optical device according to any of the above items, wherein the plurality of diffraction features are contained within an internally coupled optical element, and the internally coupled optical element is arranged to receive light from an image source and couple the light into the substrate, in such a way that it is guided therein. (Item 22) The optical device according to any of the above items, wherein the plurality of diffraction features are contained within an optically dispersed optical element, the optically dispersed optical element receives light from an image source induced within the substrate, and is positioned to direct the light to an externally coupled optical element so as to couple out of the substrate. (Item 23) The optical device according to any of the above items, wherein the plurality of diffraction features are contained within an external coupling optical element, and the external coupling optical element is arranged to receive light from an image source induced within the substrate and to couple the light out of the substrate. [Brief explanation of the drawing]

[0648] [Figure 1]Figure 1 shows an illustrative augmented reality scenario.

[0649] [Figure 2] Figure 2 shows an example of a wearable display system.

[0650] [Figure 3] Figure 3 shows a conventional display system for simulating a 3D image for the user.

[0651] [Figure 4] Figure 4 illustrates aspects of an approach to simulating a 3D image using multiple depth planes.

[0652] [Figure 5] Figures 5A-5C illustrate the relationship between distance and ray divergence.

[0653] [Figure 6] Figure 6 illustrates an example of a waveguide stack for outputting image information to the user.

[0654] [Figure 7] Figure 7 illustrates an example of an output beam generated by a waveguide.

[0655] [Figure 8] Figure 8 illustrates an example of a stacked waveguide assembly.

[0656] [Figure 9A] Figure 9A is a cross-sectional side view of an embodiment of multiple stacked waveguides.

[0657] [Figure 9B] Figure 9B is a perspective view of an embodiment of the multiple stacked waveguides shown in Figure 9A.

[0658] [Figure 9C]Figure 9C is a top and bottom plan view of the embodiment of the multiple stacked waveguides shown in Figures 9A and 9B.

[0659] [Figure 10A] Figure 10A shows an exemplary method for patterning waveguides containing materials with high refractive indices.

[0660] [Figure 10B] Figure 10B shows an exemplary method for fabricating a patterned waveguide containing a high refractive index material.

[0661] [Figure 10C] Figure 10C shows an exemplary method for fabricating a patterned waveguide containing a high refractive index material.

[0662] [Figure 10D] Figure 10D shows an implementation of a waveguide containing a high refractive index material.

[0663] [Figure 11A] Figure 11A shows an exemplary method for directly patterning a waveguide containing LiNbO3 using an etching mask.

[0664] [Figure 11B] Figure 11B shows an exemplary method for directly patterning a waveguide containing LiNbO3 using an etching mask.

[0665] [Figure 11C] Figure 11C shows an exemplary method for directly patterning a waveguide containing LiNbO3 using an etching mask.

[0666] [Figure 11D] Figure 11D illustrates a method for directly patterning a waveguide containing LiNbO3 using an etching mask.

[0667] [Figure 12A]Figure 12A shows an example of a patternable layer with a patterned inclination, which is placed on the surface of a waveguide.

[0668] [Figure 12B] Figures 12B-1 and 12B-2 illustrate exemplary methods for fabricating waveguides, including a grid-like feature used as a positive mask.

[0669] [Figure 12C] Figure 12C illustrates an exemplary method for fabricating a waveguide that includes a grid-like feature used as a negative mask.

[0670] [Figure 13-1] Figure 13A shows a grid-like imprint template for imprinting resist material.

[0671] [Figure 13-2] Figures 13B-13D illustrate various steps for fabricating a waveguide with variable height characteristics.

[0672] [Figure 14] Figures 14A and 14B illustrate exemplary polymer layers, including their features.

[0673] [Figure 15] Figures 15A and 15B illustrate the various steps involved in manufacturing a waveguide with a grid pattern.

[0674] [Figure 16A-1] Figure 16A-1 shows an exemplary waveguide including a multilayer coating.

[0675] [Figure 16A-2] Figure 16A-2 shows an exemplary waveguide with multiple features.

[0676] [Figure 16B-1] Figure 16B-1 illustrates an exemplary etching mask for fabricating a waveguide.

[0677] [Figure 16B-2a] Figures 16B-2a and 16B-2b show exemplary waveguides with multiple features. [Figure 16B-2b] Figures 16B-2a and 16B-2b show exemplary waveguides with multiple features.

[0678] [Figure 16C-1] Figure 16C-1 is an exemplary waveguide that can be etched to form the waveguide shown in Figure 16C-2.

[0679] [Figure 16C-2] Figure 16C-2 shows an exemplary waveguide with multiple features.

[0680] [Figure 17-1] Figures 17A-17E illustrate various exemplary methods for depositing materials with specific refractive indices. [Figure 17-2] Figures 17A-17E illustrate various exemplary methods for depositing materials with specific refractive indices.

[0681] [Figure 18] Figures 18A-18D show various exemplary waveguides with multiple features.

[0682] [Figure 19] Figures 19A–19D show various exemplary waveguides, including planarization layers arranged across multiple features.

[0683] [Figure 20] Figures 20A and 20B show various exemplary waveguides containing high refractive index material between the planarization layer and multiple features.

[0684] [Figure 21] Figure 21 shows an exemplary waveguide including optical elements.

[0685] [Figure 22] Figures 22A-22D show various exemplary waveguides containing materials with a certain refractive index.

[0686] [Figure 23] Figures 23A-23C illustrate various exemplary deposition techniques for depositing an anti-reflective layer on multiple features.

[0687] [Figure 24] Figures 24A–24H illustrate various exemplary coatings or structures provided across optical elements.

[0688] [Figure 25] Figures 25A and 25B show various exemplary waveguides configured to exclude or reduce light.

[0689] [Figure 26-1] Figures 26A–26G show various exemplary waveguides with one or more structural stabilization layers. [Figure 26-2] Figures 26A–26G show various exemplary waveguides with one or more structural stabilization layers. [Figure 26-3] Figures 26A–26G show various exemplary waveguides with one or more structural stabilization layers. [Figure 26-4] Figures 26A–26G show various exemplary waveguides with one or more structural stabilization layers.

[0690] [Figure 27] Figures 27A-27F show various exemplary waveguides integrated with different lenses.

[0691] [Figure 28-1] Figures 28A-28D show various exemplary devices, including the diffraction characteristics of diffractive optical elements. [Figure 28-2] Figures 28A-28D show various exemplary devices, including the diffraction characteristics of diffractive optical elements.

[0692] [Figure 29A] Figure 29A shows exemplary stepwise layers of a patternable material.

[0693] [Figure 29B] Figure 29B shows an exemplary substrate, which gradually increases with lateral position.

[0694] [Figure 30A] Figures 30A-30C show exemplary optical devices, including diffraction features. [Figure 30B] Figures 30A-30C show exemplary optical devices, including diffraction features. [Figure 30C] Figures 30A-30C show exemplary optical devices, including diffraction features.

[0695] [Figure 31] Figure 31 shows an exemplary optical device, including diffraction features.

[0696] [Figure 32] Figure 32 shows an exemplary optical device, including diffraction features.

[0697] [Figure 33A] Figure 33A is a cross-sectional side view of an exemplary device, including diffraction features.

[0698] [Figure 33B] Figure 33B is a top view of the exemplary device shown in Figure 33A.

[0699] [Figure 34] Figure 34 is a perspective view of an exemplary device, including a 2D array of diffraction features.

[0700] [Figure 35A] Figure 35A is a cross-sectional side view of an exemplary array of symmetric diffraction features.

[0701] [Figure 35B]Figure 35B is a top view of the exemplary array shown in Figure 35A.

[0702] [Figure 36] Figure 36 is a perspective view of an exemplary device, including a 2D array of diffraction features.

[0703] [Figure 36A] Figure 36A is a cross-sectional side view of an exemplary device, including diffraction features.

[0704] [Figure 36B] Figure 36B is a top view of the exemplary device shown in Figure 36A.

[0705] [Figure 37A] Figure 37A is a perspective view of an exemplary device, including a 2D array of diffraction features.

[0706] [Figure 37B] Figure 37B illustrates an exemplary diffraction feature that directs light in two directions.

[0707] [Figure 38A] Figure 38A illustrates an exemplary method for forming a blazed lattice.

[0708] [Figure 38B] Figure 38B illustrates an exemplary method for forming blazed diffraction features.

[0709] [Figure 39] Figure 39 illustrates an exemplary method for forming blazed diffraction features.

[0710] The drawings are provided to illustrate exemplary embodiments and are not intended to limit the scope of this disclosure. Similar reference numbers refer to similar parts throughout. [Modes for carrying out the invention]

[0711] VR and AR experiences may be provided by a display system having a display that provides the viewer with images corresponding to multiple depth planes. The images may differ for each depth plane (e.g., providing slightly different presentations of a scene or object) and be individually focused by the viewer's eyes, thereby helping to provide the user with depth cues based on the eye's accommodation. The eye's accommodation can focus on different content located on different depth planes within a scene. As discussed herein, such depth cues help provide the viewer with a reliable perception of depth.

[0712] In some configurations, a full-color image can be formed with respect to various depth planes by overlaying component images, each having a specific primary color. For example, red, green, and blue images may be output to form each full-color image. As a result, each depth plane may have multiple primary color images associated with it. As disclosed herein, the primary color images may be output using a waveguide that internally couples light containing image information, disperses the internally coupled light across the waveguide, and then externally couples the light toward the viewer. The light may be internally coupled into the waveguide using an internal coupling optical element such as a diffraction element (e.g., a diffraction grating), and then externally coupled out of the waveguide using an external coupling optical element, which may also be a diffraction element such as a grating.

[0713] In some implementations, light from one or more waveguides made of high refractive index materials (e.g., materials with a refractive index higher than that of glass and / or materials with a refractive index higher than or equal to about 1.8) can be externally coupled over a wider angular range compared to the angular range of light externally coupled from one or more waveguides made of materials such as glass or other materials with a refractive index of less than about 1.8. Therefore, the field of view of a display device comprising one or more waveguides made of high refractive index materials (e.g., materials with a refractive index higher than that of glass and / or materials with a refractive index of about 1.8 or higher) can exceed the field of view of a display device comprising one or more glass waveguides or one or more waveguides made of materials with a refractive index of less than about 1.8.

[0714] In addition, the efficiency of internally coupling different wavelengths of incident light into a single waveguide made of a high refractive index material (e.g., a material with a refractive index higher than that of glass and / or a material with a refractive index of about 1.8 or higher) may also exceed the efficiency of internally coupling different wavelengths of incident light into a single waveguide made of glass or a material with a refractive index of less than about 1.8. For example, in various implementations of the display devices described herein, a single waveguide made of a high refractive index material (e.g., a material with a refractive index higher than that of glass and / or a material with a refractive index of about 1.8 or higher) may efficiently internally couple red, green, and blue image light emitted from a projector, and project the red, green, and blue images toward the viewer with an increased field of view. In some implementations of display devices, a single waveguide made of a material with a high refractive index (e.g., a material with a refractive index higher than that of glass and / or a refractive index of about 1.8 or higher) can efficiently internally couple two colors of image light emitted from a projector, such as red and green or green and blue image light, and project those images (e.g., red and green or green and blue image) toward the viewer with an increased field of view. In various implementations, a single internal coupling optical element can be used to internally couple two or more colors of light into a single waveguide made of a material with a high refractive index (e.g., a material with a refractive index higher than that of glass and / or a refractive index of about 1.8 or higher). In some implementations, different internal coupling optical elements configured to internally couple different colors of light can internally couple two or more colors of light into a single waveguide made of a material with a high refractive index (e.g., a material with a refractive index higher than that of glass and / or a refractive index of about 1.8 or higher). In various embodiments, the internal coupling optical element may comprise a one-dimensional, two-dimensional, or three-dimensional grating. In various implementations, the grating can have a short-axis pitch of approximately 300 nm to approximately 450 nm. In some embodiments, the long-axis pitch of the grating of the internally coupled optical element can be approximately 300 nm to approximately 900 nm.The duty cycle / filling ratio of the internally coupled optical element can be about 10% to about 90% in various embodiments. The height or depth of the grating of the internally coupled optical element can be about 5 nm to about 500 nm in various embodiments. The grating structure of the internally coupled optical element can feature various shapes, such as lines, columns, inclined lines or columns, sawtooth, stairs, etc. Columns can have various shapes, including, but are not limited to, circles, squares, rectangles, ellipsoids, triangles, and polygons.

[0715] Therefore, a display system comprising one or more waveguides made of a material with a high refractive index (e.g., a material with a refractive index higher than that of glass and / or a material with a refractive index of about 1.8 or higher) may be attractive. The present invention describes a system and method for fabricating a lattice structure or diffractive optical element on one or more surfaces of one or more waveguides made of a material with a high refractive index (e.g., a material with a refractive index higher than that of glass and / or a material with a refractive index of about 1.8 or higher), and a resulting device that may utilize such a lattice or diffractive optical element.

[0716] Here, we refer to the drawings, where similar reference numbers refer to the same parts throughout.

[0717] Figure 2 illustrates an embodiment of a wearable display system 60. The display system 60 includes a display 70 and various mechanical and electronic modules and systems to support the functions of the display 70. The display 70 is wearable by a display system user or viewer 90 and may be coupled to a frame 80 configured to position the display 70 in front of the user 90's eyes. In some embodiments, the display 70 may be considered eyewear. In some embodiments, a speaker 100 is coupled to the frame 80 and configured to be positioned adjacent to the user 90's ear canal (in some embodiments, another speaker, not shown, may also be optionally positioned adjacent to the user's other ear canal to provide stereo / shapeable sound control). The display system also includes one or more microphones 110 or other devices to detect sound. In some embodiments, the microphones may be configured to allow the user to provide input or commands (e.g., selection of voice menu commands, natural language questions, etc.) to the system 60 and / or to enable audio communication with other persons (e.g., other users of a similar display system). The microphone may also be configured as a peripheral sensor to collect audio data (e.g., sounds from the user and / or the environment). In some embodiments, the display system may also include peripheral sensors 120a, which are separate from the frame 80 and can be mounted on the user 90's body (e.g., the user 90's head, torso, limbs, etc.). In some embodiments, the peripheral sensors 120a may be configured to obtain data characterizing the user 90's physiological state. For example, the sensors 120a may be electrodes.

[0718] Continuing with Figure 2, the display 70 is operably coupled to a local data processing module 140, which can be mounted in various configurations, such as being fixedly attached to the frame 80, fixedly attached to a helmet or hat worn by the user, built into headphones, or otherwise detachably attached to the user 90 (e.g., in a backpack configuration, in a belt-coupled configuration), via a communication link 130, such as by wired or wireless connectivity. Similarly, the sensor 120a may be operably coupled to the local data processing module 140 via a communication link 120b, such as wired or wireless connectivity. The local processing and data module 140 may include a hardware processor and digital memory such as non-volatile memory (e.g., flash memory or a hard disk drive), both of which may be used to assist in data processing, caching, and storage. The data includes a) data captured from sensors such as image capture devices (cameras, etc.), microphones, inertial measurement units, accelerometers, compasses, GPS units, wireless devices, gyroscopes, and / or other sensors disclosed herein (for example, operably coupled to frame 80 or otherwise attached to user 90), and / or b) possibly data obtained and / or processed using the remote processing module 150 and / or remote data repository 160 (including data related to virtual content) for passage to display 70 after processing or reading. The local processing and data module 140 may be operably coupled to the remote processing module 150 and the remote data repository 160 by communication links 170, 180 via wired or wireless communication links, etc., so that these remote modules 150, 160 are operably coupled to each other and available as resources to the local processing and data module 140.In some embodiments, the local processing and data module 140 may include one or more of the following: an image acquisition device, a microphone, an inertial measurement unit, an accelerometer, a compass, a GPS unit, a wireless device, and / or a gyroscope. In some other embodiments, one or more of these sensors may be mounted on the frame 80 or may be independent structures communicating with the local processing and data module 140 via a wired or wireless communication path.

[0719] Continuing to refer to Figure 2, in some embodiments, the remote processing module 150 may comprise one or more processors configured to analyze and process data and / or image information. In some embodiments, the remote data repository 160 may comprise digital data storage equipment, which may be available through the internet or other networking configurations in a “cloud” resource configuration. In some embodiments, the remote data repository 160 may comprise one or more remote servers that provide information, for example, information for generating augmented reality content, to the local processing and data module 140 and / or the remote processing module 150. In some embodiments, all data is stored, and all calculations are performed in the local processing and data module, enabling fully autonomous use from the remote module.

[0720] Referring here to Figure 3, the perception of an image as "three-dimensional" or "3-D" can be achieved by providing slightly different presentations of the image to each eye of the viewer. Figure 3 illustrates a conventional display system for simulating a three-dimensional image for a user. Two distinctly different images 190, 200 are output to the user, one for each eye 210, 220. Images 190, 200 are spaced only 230 units apart from eyes 210, 220 along the optical or z-axis parallel to the viewer's line of sight. Images 190, 200 are flat, and eyes 210, 220 can focus on the image by taking a single perspective-accommodated state. Such a 3-D display system relies on the human visual system, combines images 190, 200, and provides a perception of depth and / or scale of the combined image.

[0721] However, it should be understood that the human visual system is more complex and providing a realistic perception of depth is more difficult. For example, many viewers of conventional "3-D" display systems may find such systems uncomfortable or may not perceive any sense of depth at all. While not limited by theory, it is thought that viewers of objects may perceive them as "three-dimensional" due to a combination of convergence-divergence movements and accommodation. The convergence-divergence movements of two eyes relative to each other (i.e., rotational movement of the pupils toward or away from each other to converge the lines of sight of the eyes and fixate on an object) are closely related to the focusing (or "accommodation") of the eye's lens and pupil. Under normal conditions, changing the focus of the eye's lens, or accommodating the eye to change focus from one object to another object at a different distance, will automatically produce a corresponding change in convergence-divergence movements toward the same distance, under the relationship known as the "accommodation-convergence-divergence reflex" and pupil dilation or constriction. Similarly, changes in convergence and divergence movements will, under normal conditions, induce corresponding changes in lens shape and pupil size that match accommodation. As described herein, many stereoscopic or "3-D" display systems display scenes using slightly different presentations (and therefore slightly different images) to each eye so that a three-dimensional viewpoint is perceived by the human visual system. However, such systems, above all, simply provide different presentations of scenes, but are uncomfortable for many viewers because they act against the "accommodation-convergence-divergence reflex" when the eye views all image information in a single accommodated state. A display system that provides a better match between accommodation and convergence-divergence movements can form a more realistic and comfortable simulation of a three-dimensional image.

[0722] Figure 4 illustrates aspects of an approach to simulating a three-dimensional image using multiple depth planes. Referring to Figure 4, objects at various distances from eyes 210, 220 on the z-axis are accommodated by eyes 210, 220 so that those objects are in focus. Eyes 210, 220 take on specific accommodated states to focus objects at different distances along the z-axis. As a result, a specific accommodated state can be associated with a particular of the depth planes 240, which has an associated focal length such that an object or part of an object in a particular depth plane is in focus when the eye is in the accommodated state for that depth plane. In some embodiments, the three-dimensional image may be simulated by providing a different presentation of the image for each eye 210, 220, and by providing a different presentation of the image corresponding to each depth plane. For the sake of clarity in the illustration, although shown as separate, it should be understood that the fields of view of eyes 210, 220 may overlap, for example, as the distance along the z-axis increases. Furthermore, although shown as flat for the sake of illustration, it should be understood that the contour of the depth plane can be curved in physical space so that all features within the depth plane are in focus with the eye in a particular state of perspective adjustment.

[0723] The distance between an object and the eye 210 or 220 can also change the amount of light diverging from that object as visible to that eye. Figures 5A-5C illustrate the relationship between distance and ray divergence. The distance between the object and the eye 210 is expressed in the order of decreasing distances R1, R2, and R3. As shown in Figures 5A-5C, the rays diverge more as the distance to the object decreases. As the distance increases, the rays become more collimated. In other words, the light field generated by a point (object or part of an object) can be said to have a spherical wavefront curvature, which is a function of the distance the point is from the user's eye. The curvature increases with decreasing distance between the object and the eye 210. Consequently, in different depth planes, the ray divergence is also different, and the divergence increases with decreasing distance between the depth plane and the viewer's eye 210. Only a single eye 210 is illustrated in Figures 5A–5C and other figures herein for the sake of clarity in the illustration; however, it should be understood that the discussion relating to eye 210 may apply to both eyes 210 and 220 of the viewer.

[0724] While not limited by theory, the human eye is typically thought to be capable of interpreting a finite number of depth planes and providing depth perception. Consequently, a highly realistic simulation of perceived depth can be achieved by providing the eye with different presentations of images corresponding to each of these limited number of depth planes. These different presentations can be individually focused by the viewer's eye and thereby help provide the user with depth cues based on the eye's accommodation required to focus on different image features for scenes located on different depth planes, and / or based on observing different image features on different depth planes that are out of focus.

[0725] Figure 6 illustrates an embodiment of a waveguide stack for outputting image information to a user. The display system 250 includes a waveguide stack or stacked waveguide assembly 260, which may be used to provide three-dimensional perception to the eye / brain using a plurality of waveguides 270, 280, 290, 300, 310. In some embodiments, the display system 250 is the system 60 in Figure 2, and Figure 6 shows some parts of that system 60 in more detail. For example, the waveguide assembly 260 may be part of the display 70 in Figure 2. It should be understood that the display system 250 may be considered a light field display in some embodiments. In addition, the waveguide assembly 260 may also be referred to as an eyepiece.

[0726] Continuing with Figure 6, the waveguide assembly 260 may also include several features 320, 330, 340, and 350 between the waveguides. In some embodiments, features 320, 330, 340, and 350 may be one or more lenses. Waveguides 270, 280, 290, 300, and 310, and / or several lenses 320, 330, 340, and 350 may be configured to transmit image information to the eye using various levels of wavefront curvature or ray divergence. Each waveguide level may be associated with a specific depth plane and may be configured to output image information corresponding to that depth plane. Image input devices 360, 370, 380, 390, and 400 may function as light sources for the waveguides and may be used to input image information into the waveguides 270, 280, 290, 300, and 310, each of which may be configured to disperse incident light across each individual waveguide for output toward the eye 210, as described herein. The light exits from the output surfaces 410, 420, 430, 440, and 450 of the image input devices 360, 370, 380, 390, and 400 and is input into the corresponding input surfaces 460, 470, 480, 490, and 500 of the waveguides 270, 280, 290, 300, and 310. In some embodiments, the input surfaces 460, 470, 480, 490, and 500 may each be the edge of the corresponding waveguide or a portion of the main surface of the corresponding waveguide (i.e., one of the waveguide surfaces directly facing the world 510 or the viewer's eye 210). In some embodiments, a single beam of light (e.g., a collimated beam) may be injected into each waveguide and output a cloned collimated beam whole field that is directed toward the eye 210 at a specific angle (and divergence) corresponding to the depth plane associated with the particular waveguide. In some embodiments, one of the image input devices 360, 370, 380, 390, and 400 may be associated with a plurality (e.g., three) of waveguides 270, 280, 290, 300, and 310 and injected into them.

[0727] In some embodiments, the image input devices 360, 370, 380, 390, and 400 are discrete displays, each generating image information for input into the corresponding waveguides 270, 280, 290, 300, and 310, respectively. In some other embodiments, the image input devices 360, 370, 380, 390, and 400 are output terminals of a single multiplexed display, which can send image information to each of the image input devices 360, 370, 380, 390, and 400, for example, via one or more optical conduits (such as optical fiber cables). It should be understood that the image information provided by the image input devices 360, 370, 380, 390, and 400 may include light of different wavelengths or colors (e.g., different primary colors, as discussed herein).

[0728] In some embodiments, the light introduced into waveguides 270, 280, 290, 300, and 310 is provided by an optical projector system 520 comprising an optical module 540, which may include an optical emitter such as a light-emitting diode (LED). The light from the optical module 540 may be directed and modified via a beam splitter 550 to an optical modulator 530, for example, a spatial light modulator. The optical modulator 530 may be configured to change the perceived intensity of the light introduced into waveguides 270, 280, 290, 300, and 310. Embodiments of the spatial light modulator include liquid crystal displays (LCDs), including liquid crystal on silicon (LCOS) displays. Image input devices 360, 370, 380, 390, and 400 are graphically illustrated, and it should be understood that in some embodiments, these image input devices may represent different optical paths and locations within a common projection system, configured to output light into associated waveguides 270, 280, 290, 300, and 310.

[0729] In some embodiments, the display system 250 may be a scanning fiber display comprising one or more scanning fibers configured to project light in various patterns (e.g., raster scanning, helical scanning, Lissajous patterns, etc.) into one or more waveguides 270, 280, 290, 300, 310, and ultimately to the viewer's eye 210. In some embodiments, the illustrated image input devices 360, 370, 380, 390, 400 may schematically represent a single scanning fiber or a bundle of scanning fibers configured to input light into one or more waveguides 270, 280, 290, 300, 310. In some other embodiments, the illustrated image input devices 360, 370, 380, 390, 400 may schematically represent multiple scanning fibers or multiple bundles of scanning fibers, each configured to input light into the associated waveguide 270, 280, 290, 300, 310. It should be understood that one or more optical fibers may be configured to transmit light from the optical module 540 to one or more waveguides 270, 280, 290, 300, and 310. It should also be understood that one or more intervening optical structures may be provided between the scanning fiber or multiple fibers and one or more waveguides 270, 280, 290, 300, and 310, for example, to redirect light emitted from the scanning fiber into one or more waveguides 270, 280, 290, 300, and 310.

[0730] The controller 560 controls the operation of one or more of the stacked waveguide assemblies 260, including the operation of the image input devices 360, 370, 380, 390, 400, the light source 540, and the optical modulator 530. In some embodiments, the controller 560 is part of the local data processing module 140. The controller 560 includes programming (e.g., instructions in a non-transient medium) to coordinate the timing and delivery of image information to the waveguides 270, 280, 290, 300, 310, for example, according to any of the various schemes disclosed herein. In some embodiments, the controller may be a single integrated device or a distributed system connected by wired or wireless communication channels. In some embodiments, the controller 560 may be part of the processing module 140 or 150 (Figure 2).

[0731] Continuing with Figure 6, the waveguides 270, 280, 290, 300, and 310 may be configured to propagate light within each individual waveguide by total internal reflection (TIR). Each waveguide 270, 280, 290, 300, and 310 may be planar or have another shape (e.g., curved), with a main upper surface and a bottom surface and edges extending between their main upper and bottom surfaces. In the illustrated configuration, each waveguide 270, 280, 290, 300, and 310 may include external coupling optical elements 570, 580, 590, 600, and 610, respectively, configured to extract light from the waveguide by redirecting the light propagating within each individual waveguide out of the waveguide and outputting image information to the eye 210. The extracted light may also be referred to as external coupling light, and the external coupling optical element light may also be referred to as light extraction optical element. The extracted beam of light can be output by the waveguide at the point where light propagating within the waveguide strikes the light extraction optical element. The external coupling optical elements 570, 580, 590, 600, 610 may be gratings, for example, including diffractive optical features as further discussed herein. For the sake of clarity and to facilitate the explanation, they are shown positioned on the bottom main surfaces of the waveguides 270, 280, 290, 300, 310, but in some embodiments, the external coupling optical elements 570, 580, 590, 600, 610 may be positioned on the top and / or bottom main surfaces, and / or directly within the volume of the waveguides 270, 280, 290, 300, 310, as further discussed herein. In some embodiments, the external coupling optical elements 570, 580, 590, 600, 610 may be mounted on a transparent substrate and formed within a layer of material that forms the waveguides 270, 280, 290, 300, 310. In some other embodiments, the waveguides 270, 280, 290, 300, 310 may be a monolithic piece of material, and the external coupling optical elements 570, 580, 590, 600, 610 may be formed on and / or inside the material piece.

[0732] Continuing with reference to Figure 6, as discussed herein, each waveguide 270, 280, 290, 300, 310 is configured to emit light and form an image corresponding to a specific depth plane. For example, the waveguide 270 closest to the eye may be configured to deliver collimated light (injected into such waveguide 270) to the eye 210. The collimated light may represent the optical infinity focal plane. The next upper waveguide 280 may be configured to emit collimated light that passes through a first lens 350 (e.g., a negative lens) before reaching the eye 210. Such a first lens 350 may generate some convex wavefront curvature so that the eye / brain interprets the light originating from the next upper waveguide 280 as originating from a first focal plane closer inward from optical infinity toward the eye 210. Similarly, the third upper waveguide 290 may pass its output light through both the first lens 350 and the second lens 340 before reaching the eye 210, and the combined refractive power of the first lens 350 and the second lens 340 may be configured to generate another gradually increasing wavefront curvature so that the eye / brain interprets the light originating from the third waveguide 290 as originating from a second focal plane that is closer inward toward the person from optical infinity than the light originating from the next upper waveguide 280.

[0733] Other waveguide layers 300, 310 and lenses 330, 320 are configured similarly, with the highest waveguide 310 in the stack emitting its output through all the lenses between it and the eye for a convergent focusing force representing the focal plane closest to the person. When viewing / interpreting light originating from the other side world 510 of the stacked waveguide assembly 260, a compensating lens layer 620 may be positioned on top of the stack to compensate for the convergent forces of the lower lens stacks 320, 330, 340, 350 to compensate for the stack of lenses 320, 330, 340, 350. Such a configuration provides the same number of perceived focal planes as there are available waveguide / lens pairs. Both the external coupling optical elements of the waveguides and the focusing sides of the lenses may be static (i.e., not dynamic or electroactive). In some alternative embodiments, one or both may be dynamic using electroactive features.

[0734] In some embodiments, two or more of the waveguides 270, 280, 290, 300, and 310 may have the same associated depth plane. For example, multiple waveguides 270, 280, 290, 300, and 310 may be configured to output images set in the same depth plane, or multiple subsets of waveguides 270, 280, 290, 300, and 310 may be configured to output images set in the same multiple depth planes, with one set for each depth plane. This may offer the advantage of forming tiled images that provide an extended field of view in those depth planes.

[0735] Continuing with Figure 6, the external coupling optical elements 570, 580, 590, 600, and 610 may be configured to redirect light outward from their individual waveguides for specific depth planes associated with the waveguides, and to output the light with an appropriate amount of divergence or collimation. As a result, waveguides having different associated depth planes may have external coupling optical elements 570, 580, 590, 600, and 610 with different configurations, outputting light with different amounts of divergence depending on the associated depth plane. In some embodiments, the light extraction optical elements 570, 580, 590, 600, and 610 may be three-dimensional or surface features that can be configured to output light at specific angles. For example, the light extraction optical elements 570, 580, 590, 600, and 610 may be three-dimensional holograms, surface holograms, and / or diffraction gratings. In some embodiments, features 320, 330, 340, and 350 do not have to be lenses; rather, they may simply be spacers (e.g., cladding layers and / or structures for forming voids).

[0736] In some embodiments, the external coupling optical elements 570, 580, 590, 600, 610 are diffraction features or “diffractive optical elements” (also referred to herein as “DOEs”) that form a diffraction pattern. Preferably, the DOEs have sufficiently low diffraction efficiency such that only a portion of the beam light is deflected toward the eye 210 at each intersection of the DOEs, while the remainder continues to travel through the waveguide via the TIR. The light carrying the image information is therefore split into several associated emission beams that exit the waveguide at multiple locations, resulting in a very uniform pattern of emission toward the eye 210 with respect to this particular collimated beam bouncing within the waveguide.

[0737] In some embodiments, one or more DOEs may be switchable between an "on" state in which they actively diffract and an "off" state in which they do not significantly diffract. For example, a switchable DOE may comprise a layer of polymer-dispersed liquid crystal where microdroplets have a diffraction pattern within the host medium, and the refractive index of the microdroplets may be switched to substantially match the refractive index of the host material (in which case the pattern does not significantly diffract incident light), or the microdroplets may be switched to a refractive index that does not match that of the host medium (in which case the pattern actively diffracts incident light).

[0738] In some embodiments, a camera assembly 630 (e.g., a digital camera including visible and infrared cameras) may be provided to capture images of the eye 210 and / or the surrounding tissues, for example, to detect user input and / or monitor the user's physiological state. As used herein, the camera may be any image-capturing device. In some embodiments, the camera assembly 630 may include the image-capturing device and a light source that projects light (e.g., infrared light) onto the eye, which is then reflected by the eye and can be detected by the image-capturing device. In some embodiments, the camera assembly 630 may be mounted on a frame 80 (Figure 2) and may communicate with processing modules 140 and / or 150 that can process image information from the camera assembly 630. In some embodiments, one camera assembly 630 may be used per eye to monitor each eye separately.

[0739] Referring here to Figure 7, an embodiment of an outgoing beam output by a waveguide is shown. Although one waveguide is illustrated, other waveguides within the waveguide assembly 260 (Figure 6) may function similarly, and it should be understood that the waveguide assembly 260 includes multiple waveguides. Light 640 is introduced into the waveguide 270 at the input surface 460 of the waveguide 270 and propagates through the waveguide 270 by TIR. At the point where the light 640 collides on the DOE 570, a portion of the light exits the waveguide as an outgoing beam 650. The outgoing beam 650 is illustrated as substantially parallel, but may be redirected to propagate to the eye 210 at a certain angle (e.g., forming a divergent outgoing beam), depending on the depth plane associated with the waveguide 270, as discussed herein. It should be understood that a nearly parallel emitted beam may represent a waveguide with an externally coupled optical element that externally couples the light to form an image that appears to be set in the depth plane at a distance from the eye 210 (e.g., optical infinity). Other waveguides or other sets of externally coupled optical elements may output a more divergent emitted beam pattern, which would require the eye 210 to adjust to a closer distance and focus onto the retina, and would be interpreted by the brain as light from a distance closer to the eye 210 than optical infinity.

[0740] In some embodiments, a full-color image may be formed in each depth plane by overlaying an image onto each of primary colors, for example, three or more primary colors. Figure 8 illustrates an embodiment of a stacked waveguide assembly in which each depth plane includes an image formed using multiple different primary colors. The illustrated embodiment shows depth planes 240a–240f, but more or fewer depths may also be considered. Each depth plane may have three or more associated primary color images, including a first image of a first color G, a second image of a second color R, and a third image of a third color B. Different depth planes are indicated in the figure by different numbers relating to diopters (dpt) following the letters G, R, and B. As merely an embodiment, the numbers following each of these letters indicate diopters (1 / m), i.e., the inverse distance of the depth plane from the viewer, and each box in the figure represents an individual primary color image. In some embodiments, the precise location of the depth plane for different primary colors may vary to account for differences in the focusing of light of different wavelengths in the eye. For example, different primary color images for a given depth plane may be placed on depth planes corresponding to different distances from the user. Such arrangements may increase visual acuity and user comfort and / or reduce chromatic aberration.

[0741] In some embodiments, each primary color light may be output by a single dedicated waveguide, and as a result, each depth plane may have multiple waveguides associated with it. In such embodiments, each box in the figure, including the letters G, R, or B, can be understood to represent an individual waveguide, and three waveguides may be provided per depth plane, with three primary color images provided per depth plane. The waveguides associated with each depth plane are shown adjacent to each other in this drawing for ease of explanation, but it should be understood that in a physical device, all waveguides may be arranged in a stack with one waveguide per level. In some other embodiments, multiple primary colors may be output by the same waveguide, for example, so that only a single waveguide may be provided per depth plane.

[0742] Continuing to refer to Figure 8, in some embodiments, G is green, R is red, and B is blue. In some other embodiments, other colors associated with other wavelengths of light, including magenta and cyan, may be used in addition to or replace one or more of red, green, or blue.

[0743] It should be understood that any reference to a given color of light throughout this disclosure will be understood to encompass light of one or more wavelengths within a range of wavelengths that are perceived by the viewer as that given color. For example, red light may include light of one or more wavelengths in the range of approximately 620–780 nm, green light may include light of one or more wavelengths in the range of approximately 492–577 nm, and blue light may include light of one or more wavelengths in the range of approximately 435–493 nm.

[0744] In some embodiments, the light source 540 (Figure 6) may be configured to emit light of one or more wavelengths outside the viewer's visual perception range, such as infrared and / or ultraviolet wavelengths. In addition, internal coupling, external coupling, and other light redirection structures of the waveguide of the display 250 may be configured to direct and emit this light from the display towards the user's eye 210, for example, for imaging and / or user stimulation applications.

[0745] Referring here to Figure 9A, in some embodiments, light impacting a waveguide may need to be redirected to internally couple that light into the waveguide. Internal coupling optical elements may be used to redirect and internally couple the light into its corresponding waveguide. Figure 9A illustrates cross-sectional side views of embodiments of multiple or set 660 stacked waveguides, each including an internal coupling optical element. Each waveguide may be configured to output light of one or more different wavelengths or one or more different wavelength ranges. Stack 660 may correspond to stack 260 (Figure 6), and the illustrated waveguides of stack 660 may correspond to a portion of multiple waveguides 270, 280, 290, 300, 310, but it should be understood that light from one or more of the image input devices 360, 370, 380, 390, 400 is input into the waveguide from a position where the light is required to be redirected for internal coupling.

[0746] The illustrated set of stacked waveguides 660 includes waveguides 670, 680, and 690. Waveguide 670 is ahead of waveguide 680 or closer to the image light source than waveguide 680, and waveguide 690 is behind waveguide 680 or further away from the image light source than waveguide 680. Each waveguide includes associated internal coupling optical elements (which may also be referred to as optical input areas on the waveguide), for example, internal coupling optical element 700 is located on the main surface of waveguide 670 (e.g., the upper main surface), internal coupling optical element 710 is located on the main surface of waveguide 680 (e.g., the upper main surface), and internal coupling optical element 720 is located on the main surface of waveguide 690 (e.g., the upper main surface). In some embodiments, one or more of the internally coupled optical elements 700, 710, 720 may be located on the bottom main surface of individual waveguides 670, 680, 690 (in particular, one or more internally coupled optical elements are reflective deflection optical elements). As shown, the internally coupled optical elements 700, 710, 720 may also be located on the upper main surface of their individual waveguides 670, 680, 690 (or the upper part of the following lower waveguide), in particular, their internally coupled optical elements are transmissive deflection optical elements. In some embodiments, the internally coupled optical elements 700, 710, 720 may be located within the body of individual waveguides 670, 680, 690. In some embodiments, as discussed herein, the internally coupled optical elements 700, 710, 720 are wavelength-selective, selectively redirecting one or more wavelengths of light while transmitting other wavelengths of light. Although illustrated on one side or corner of those individual waveguides 670, 680, 690, it should be understood that in some embodiments, the internal coupling optical elements 700, 710, 720 may be located within other areas of those individual waveguides 670, 680, 690.

[0747] As illustrated, the internally coupled optical elements 700, 710, and 720 may be offset laterally from one another. In some embodiments, each internally coupled optical element may be offset so that it receives light without its light passing through another internally coupled optical element. For example, each internally coupled optical element 700, 710, and 720 may be configured to receive light from different image input devices 360, 370, 380, 390, and 400, as shown in Figure 6, and may be separated from other internally coupled optical elements 700, 710, and 720 (e.g., separated laterally) so that it substantially does not receive light from the other internally coupled optical elements 700, 710, and 720.

[0748] Each waveguide also includes associated optical dispersion elements, for example, optical dispersion element 730 is located on the main surface (e.g., upper main surface) of waveguide 670, optical dispersion element 740 is located on the main surface (e.g., upper main surface) of waveguide 680, and optical dispersion element 750 is located on the main surface (e.g., upper main surface) of waveguide 690. In some other embodiments, optical dispersion elements 730, 740, and 750 may be located on the bottom main surfaces of the associated waveguides 670, 680, and 690, respectively. In some other embodiments, optical dispersion elements 730, 740, and 750 may be located on both the top and bottom main surfaces of the associated waveguides 670, 680, and 690, respectively, or optical dispersion elements 730, 740, and 750 may be located on different top and bottom main surfaces within different associated waveguides 670, 680, and 690, respectively.

[0749] Waveguides 670, 680, and 690 may be separated and isolated by, for example, gaseous, liquid, and / or solid layers of material. For example, as shown, layer 760a may separate waveguides 670 and 680, and layer 760b may separate waveguides 680 and 690. In some embodiments, layers 760a and 760b are formed from a low refractive index material (i.e., a material having a lower refractive index than the material forming the nearest waveguide among 670, 680, and 690). Preferably, the refractive index of the material forming layers 760a and 760b is 0.05 or greater, or 0.10 or less, than the refractive index of the material forming waveguides 670, 680, and 690. Advantageously, the lower refractive index layers 760a, 760b may function as cladding layers that promote total internal reflection (TIR) ​​of light through the waveguides 670, 680, 690 (e.g., TIR between the top and bottom main surfaces of each waveguide). In some embodiments, layers 760a, 760b are formed from air. It should be understood that the top and bottom of the illustrated set of waveguides 660 may include an immediate cladding layer, although not shown.

[0750] Preferably, to facilitate manufacturing and other considerations, the materials forming waveguides 670, 680, and 690 are similar or identical, and the materials forming layers 760a and 760b are similar or identical. In some embodiments, the materials forming waveguides 670, 680, and 690 may differ between one or more waveguides, and / or the materials forming layers 760a and 760b may still differ while maintaining the various refractive index relationships described above.

[0751] Continuing to refer to Figure 9A, rays 770, 780, and 790 are incident on the set of waveguides 660. It should be understood that rays 770, 780, and 790 may be injected into waveguides 670, 680, and 690 by one or more image input devices 360, 370, 380, 390, and 400 (Figure 6). Rays 770, 780, and 790 may constitute image light, i.e., light encoded with image information. For example, the light may be spatially modulated or provided in different ways with different intensities and / or different wavelengths at different locations, for example, to form pixels that form an image.

[0752] In some embodiments, the rays 770, 780, and 790 may have different properties, such as different wavelengths or different wavelength ranges, which may correspond to different colors. The internal coupling optical elements 700, 710, and 720 each deflect the incident light so that the light propagates through one of the waveguides 670, 680, and 690 by TIR. In some embodiments, the internal coupling optical elements 700, 710, and 720 each selectively deflect one or more specific wavelengths of light while allowing other wavelengths to pass through the lower waveguide and associated internal coupling optical elements.

[0753] For example, the internally coupled optical element 700 may be configured to transmit rays 780 and 790 having different second and third wavelengths or wavelength ranges, while deflecting a ray 770 having a first wavelength or wavelength range. The transmitted ray 780 collides with an internally coupled optical element 710 configured to deflect light of the second wavelength or wavelength range, and is thereby deflected. The ray 790 is deflected by an internally coupled optical element 720 configured to selectively deflect light of a third wavelength or wavelength range.

[0754] Continuing with Figure 9A, the deflected rays 770, 780, and 790 are deflected so that they propagate through the corresponding waveguides 670, 680, and 690. That is, the internal coupling optical elements 700, 710, and 720 of each waveguide deflect the light into their corresponding waveguides 670, 680, and 690, and internally couple the light into their corresponding waveguides. The rays 770, 780, and 790 are deflected at an angle that causes the light to propagate through the individual waveguides 670, 680, and 690 by TIR. The rays 770, 780, and 790 propagate through the individual waveguides 670, 680, and 690 by TIR until they collide with the corresponding optical dispersion elements 730, 740, and 750 of the waveguides.

[0755] Referring now to Figure 9B, a perspective view of an embodiment of the multiple stacked waveguides shown in Figure 9A is illustrated. As described above, the internally coupled rays 770, 780, and 790 are deflected by the internally coupled optical elements 700, 710, and 720, respectively, and then propagate by TIR within waveguides 670, 680, and 690, respectively. The rays 770, 780, and 790 then collide with the optical dispersion elements 730, 740, and 750, respectively. The optical dispersion elements 730, 740, and 750 deflect the rays 770, 780, and 790 so that they propagate toward the externally coupled optical elements 800, 810, and 820, respectively.

[0756] In some embodiments, the light dispersion elements 730, 740, and 750 are orthogonal pupil expanders (OPEs). In some embodiments, the OPEs deflect or disperse light to the external coupling optical elements 800, 810, and 820, and in some embodiments, they can also increase the beam or spot size of the light as it propagates to the external coupling optical elements. In some embodiments, the light dispersion elements 730, 740, and 750 may be omitted, and the internal coupling optical elements 700, 710, and 720 may be configured to deflect light directly to the external coupling optical elements 800, 810, and 820. For example, referring to Figure 9A, the light dispersion elements 730, 740, and 750 may be replaced by the external coupling optical elements 800, 810, and 820, respectively. In some embodiments, the external coupling optical elements 800, 810, 820 are exit pupils (EPs) or exit pupil expanders (EPEs) that direct light towards the viewer's eye 210 (Figure 7). It should be understood that the OPEs may be configured to increase the dimensions of the eyebox along at least one axis, and the EPEs may increase the eyebox along an axis intersecting, for example, orthogonal to the axis of the OPE. For example, each OPE may be configured to redirect a portion of the light impacting the OPE to an EPE in the same waveguide, while allowing the rest of the light to continue propagating along the waveguide. In response to impacting the OPE again, another portion of the remaining light is redirected to the EPE, and the rest of that portion continues to propagate further along the waveguide, etc. Similarly, in response to impacting the EPE, a portion of the impacting light may be directed out of the waveguide toward the user, and the rest of that light may continue propagating through the waveguide until it impacts the EP again, at which point another portion of the impacting light may be directed out of the waveguide, and so on. As a result, the internally coupled single beam of light is "duplicated" each time a portion of its light is redirected by the OPE or EPE, thereby forming a cloned beam field of light, as shown in Figure 6. In some embodiments, the OPE and / or EPE may be configured to modify the size of the beam of light.

[0757] Therefore, referring to Figures 9A and 9B, in some embodiments, the set of waveguides 660 includes, for each primary color, waveguides 670, 680, 690, internally coupled optical elements 700, 710, 720, optical dispersion elements (e.g., OPE) 730, 740, 750, and externally coupled optical elements (e.g., EP) 800, 810, 820. Waveguides 670, 680, 690 may be stacked with air gaps / cladding layers between each one. The internally coupled optical elements 700, 710, 720 redirect or deflect the incident light into their waveguides (using different internally coupled optical elements that receive light of different wavelengths). The light then propagates within the individual waveguides 670, 680, 690 at angles that will result in a TIR. In the embodiment shown, a ray 770 (e.g., blue light) is polarized by the first internal coupling optical element 700 in the manner described above, and then continues to bounce along the waveguide, interacting with the optical dispersion element (e.g., OPE) 730 and then the external coupling optical element (e.g., EP) 800. Rays 780 and 790 (e.g., green and red light, respectively) pass through waveguide 670, with ray 780 colliding with the internal coupling optical element 710, thereby being deflected. Ray 780 will then bounce along waveguide 680 via TIR, proceeding to its optical dispersion element (e.g., OPE) 740 and then the external coupling optical element (e.g., EP) 810. Finally, ray 790 (e.g., red light) passes through waveguide 690 and colliding with the optical internal coupling optical element 720 of waveguide 690. The internal optical coupling element 720 deflects the ray 790 so that it propagates by TIR to the optical dispersion element (e.g., OPE) 750, and then by TIR to the external coupling optical element (e.g., EP) 820. The external coupling optical element 820 then finally externally couples the ray 790 to a viewer who also receives externally coupled light from other waveguides 670, 680.

[0758] Figure 9C illustrates upper and lower plan views of embodiments of the multiple stacked waveguides shown in Figures 9A and 9B. As shown, waveguides 670, 680, and 690 may be vertically aligned with the associated optical dispersion elements 730, 740, and 750 and associated external coupling optical elements 800, 810, and 820 of each waveguide. However, as discussed herein, the internal coupling optical elements 700, 710, and 720 are not vertically aligned. Rather, the internal coupling optical elements are preferably non-overlapping (e.g., laterally spaced, as seen in the upper and lower figures). As further discussed herein, this non-overlapping spatial arrangement facilitates the ingress of light from different resources into different waveguides on a one-to-one basis, thereby enabling a specific light source to be uniquely coupled to a specific waveguide. In some embodiments, arrangements including non-overlapping, spatially separated internal coupling optical elements may be referred to as a shifted or split pupil system, where the internal coupling optical elements in these arrangements may correspond to subpupils.

[0759] As discussed above, various embodiments of the display system 60 or the display system 250 may include waveguides with high refractive index materials. For example, various embodiments of the display system 60 or the display system 250 may include one or more waveguides with a material having a refractive index higher than that of glass. Various embodiments of the display system 60 or the display system 250 may include one or more waveguides with a material having a refractive index of about 1.8 or higher and about 4.5 or lower. For example, various embodiments of the display system 60 or the display system 250 include: 1.8 or more and 2.1 or less, 2.1 or more and 2.2 or less, 2.2 or more and 2.3 or less, 2.3 or more and 2.4 or less, 2.4 or more and 2.5 or less, 2.5 or more and 2.6 or less, 2.6 or more and 2.7 or less, 2.7 or more and 2.8 or less, 2.8 or more and 2.9 or less, 2.9 or more and 3.0 or less, 3.0 or more and 3 A waveguide may be provided with a material having a refractive index of 0.1 or less, 3.1 or more and 3.2 or less, 3.2 or more and 3.3 or less, 3.3 or more and 3.4 or less, 3.4 or more and 3.5 or less, 3.5 or more and 3.6 or less, 3.6 or more and 3.7 or less, 3.7 or more and 3.8 or less, 3.8 or more and 3.9 or less, 3.9 or more and 4.0 or less, or any value within any range / sub-range defined by these values. Without loss of generality, the high refractive index materials considered in this application may be transmittable to visible light. For example, the high refractive index materials considered in this application may be configured to transmit visible light in the spectral range between approximately 450 nm and approximately 750 nm with an efficiency of 90% or more. However, Fresnel reflection may occur at the waveguide interface in some implementations.

[0760] As discussed above, various embodiments of the display system 60 or display system 250 comprising one or more waveguides with a high refractive index material (e.g., with a refractive index higher than that of glass and / or with a refractive index of about 1.8 or higher) can have an increased field of view compared to embodiments of the display system 60 or display system 250 comprising one or more waveguides with glass and / or materials with a refractive index of less than about 1.8. Furthermore, as discussed above, different colors or wavelengths of light (e.g., two or possibly three colors) can be coupled into a single waveguide made of a high refractive index material. Thus, various embodiments of the display system 60 or display system 250 can comprise different waveguides associated with different depth planes, and the waveguides associated with the depth planes can be made of a high refractive index material such that different colors or wavelengths of incident light (e.g., red, green, and blue wavelengths), etc., are coupled into their single waveguide. Therefore, the associated waveguide has the ability to project a multicolor image consisting of light of different wavelengths (e.g., red, green, and blue wavelengths) toward the viewer. The various high refractive index materials considered in this application consist of materials such as lithium niobate (LiNbO3) with a refractive index of about 2.3, silicon carbide (SiC) with a refractive index of 2.6 to 3.0, or other similar materials.

[0761] As discussed above, one or more waveguides in various implementations of the display system 60 or the display system 250 may comprise internal coupling optical elements (e.g., internal coupling optical elements 700, 710, 720) for internally coupling light into one or more waveguides, and / or external coupling optical elements (e.g., 570, 580, 590, 800, 810, 820) from one or more waveguides. In various embodiments of the display system 60 or the display system 250, one or more waveguides may comprise optical dispersion elements (e.g., optical dispersion elements 730, 740, 750). In various embodiments, the optical dispersion elements (e.g., optical dispersion elements 730, 740, 750) may be configured as orthogonal pupil expanders (OPEs), and / or the external coupling elements (e.g., 800, 810, 820) may be configured as exit pupil expanders (EPEs). The eyepiece may include one of the following: an internal coupling optical element (ICG), an orthogonal pupil expander (OPE), and an exit pupil expander (EPE), or a combination thereof. Therefore, a wide range of configurations is possible. For example, some eyepieces do not include an orthogonal pupil expander (OPE). The internal coupling optical element, external coupling optical element, and optical dispersion element may have diffraction features. The diffractive optical element may have microscale and / or nanoscale features. In various embodiments, the diffractive optical element may have variable height, pitch, and / or shape features. Without loss of generality, the internal coupling optical element, external coupling optical element, and / or optical dispersion element may be provided on one or both surfaces of the waveguide in different embodiments of the display system 60 or the display system 250. For example, various embodiments of the waveguide described herein may have a diffractive structure disposed on both surfaces of the waveguide.

[0762] Waveguides, with internally coupled optical elements, externally coupled optical elements, and / or optically dispersed elements, can be fabricated using various manufacturing processes, such as lithography, etching, patterning, and physical and / or chemical deposition methods. It may be advantageous that the manufacturing methods and techniques used to fabricate the internally coupled optical elements, externally coupled optical elements, and / or optically dispersed elements are capable of achieving uniform pattern fidelity over large areas, enabling efficient internal coupling of light into the waveguide, efficient and / or uniform distribution of light along one or more desired directions within the waveguide, efficient and / or uniform external coupling of light propagating within the waveguide, or any combination thereof. Without losing any generality, pattern fidelity may refer to the fidelity with which an imprinted pattern is transferred from a master to the surface of the substrate. Pattern fidelity is determined based on the following characteristics:

[0763] 1) Variation of the pattern on the substrate from the pattern on the master. For example, pattern fidelity may be considered high if the variation in characteristics (e.g., length, width, height, depth, angle, or surface roughness) of features (e.g., lines, holes, grooves, columns, sidewalls) is within a threshold. For example, pattern fidelity may be considered high if the variation in line width, hole diameter or column diameter, feature height or depth, sidewall angle, or line edge roughness between the pattern on the substrate and the pattern on the master is within approximately + / - 5%.

[0764] 2) The number of defects per 100 square μm or 1 square cm. In some embodiments, a variation in the characteristics of a feature may be considered a defect if it exceeds a threshold. A defect can be assigned to one of the defect size bins based on the amount of variation. For example, different defect size bins may include variation <1 μm, <5 μm, <20 μm, <50 μm, <100 μm, etc. Pattern fidelity may be considered high if the number of defects per 100 square μm or 1 square cm in the pattern on the substrate is below the threshold.

[0765] 3) Alignment of patterns across the surface of the substrate and between edges within the area of ​​the pattern. For example, pattern fidelity may be considered high if there is no distortion of one or more alignment marks and / or distortion at the edge boundaries.

[0766] Various embodiments of the display devices considered in this application may comprise a waveguide having a diffractive structure positioned on one or both surfaces of the waveguide. The diffractive structure may have a variable height and / or pitch. Such a waveguide may be configured to internally couple external light, disperse the internally coupled light along one or more desired directions, and / or externally couple the internally coupled light. In various embodiments of the display devices, such a waveguide may be configured to mitigate undesirable optical artifacts. Different methods for fabricating a waveguide having one or more surfaces having diffractive features (e.g., diffractive features with variable height and / or pitch) are described in this application. One or more of the different methods described in this application may be suitable for mass production. Some of the methods for fabricating a waveguide having one or more surfaces having diffractive features (e.g., diffractive features with variable height and / or pitch) described in this application may employ at least two different materials that are etched by an etching solution at different rates. I. Imprinted polymer patterning

[0767] One method for fabricating a diffraction structure on one or both surfaces of a waveguide includes the step of patterning one or both surfaces of the waveguide with a patternable layer. The patternable layer may consist of a polymer. For example, the patternable layer may consist of an ultraviolet (UV) curable polymer. In another embodiment, the patternable layer may consist of a resist (e.g., a polymer resist). The waveguide may consist of a material with a high refractive index (e.g., a refractive index of 1.8 or higher and / or a refractive index higher than that of glass). The patternable layer may have a refractive index lower than that of the waveguide material (e.g., a refractive index less than 1.8). For example, the refractive index of the patternable layer may be about 1.2 to about 1.8. In various embodiments, the refractive index of the patternable layer can be about 1.2 or greater and about 1.3 or less, about 1.3 or greater and about 1.4 or less, about 1.4 or greater and about 1.5 or less, about 1.5 or greater and about 1.6 or less, about 1.6 or greater and about 1.7 or less, about 1.7 or greater and about 1.8 or less, or any range / subrange between any of these values.

[0768] Patternable layers can be deposited across one or more surfaces of a waveguide using jet deposition techniques (e.g., inkjet deposition). Jet deposition techniques employ the step of dispensing a certain volume of patternable material (e.g., polymer, resist) across the waveguide using an inkjet printer head. For example, an inkjet printer head can dispense droplets of patternable material (e.g., polymer, resist) across the waveguide. In various embodiments, the dispensed volume of patternable material (e.g., polymer, resist) may vary across the waveguide surface. The accuracy in the placement of the dispensed volume of patternable material across the waveguide can be high when deposited using jet deposition techniques. In addition, jet deposition techniques allow different volumes of patternable material (e.g., polymer, resist) to be deposited in different regions of the waveguide surface. As discussed below, this characteristic of jet deposition techniques can be advantageous when fabricating features with variable height and / or pitch. Jet deposition technology can also reduce waste of patternable material (e.g., polymers, resists) compared to other deposition technologies, such as spin coating. In addition, the step of depositing patternable material (e.g., polymers, resists) using jet deposition technology can be faster compared to other deposition technologies, such as spin coating. Therefore, in some implementations, jet deposition technology can increase throughput. Using jet deposition, the thickness of the patternable layer can be controlled. For example, a patternable layer deposited by jet deposition technology may have a thickness of approximately 10 nm to approximately 1 micron (e.g., approximately 10 nm to approximately 50 nm, approximately 25 nm to approximately 75 nm, approximately 40 nm to approximately 100 nm, approximately 80 nm to approximately 300 nm, approximately 200 nm to approximately 500 nm, approximately 400 nm to approximately 800 nm, approximately 500 nm to approximately 1 micron, or any value within the range / sub-range defined by any of these values). Controlling the thickness of the deposited patternable layer can be advantageous when fabricating diffraction features with varying heights, as discussed below.In addition, patternable layers of different compositions can be deposited on different parts of the waveguide using jet deposition techniques. Patternable layers of different compositions can be etched at different rates when exposed to etching solutions. Therefore, depositing patternable layers of different compositions on different parts of the waveguide using jet deposition techniques may be advantageous when fabricating diffraction features with different heights and / or pitches, as discussed below. In various embodiments of the fabrication, other deposition methods, such as coating, spin coating, spraying, or other pre-metering coating techniques, such as slot dies, doctor blades, knife edges, screens, etc., may be employed to deposit the patternable material (e.g., polymer, resist).

[0769] For example, certain high refractive index materials such as lithium niobate (LiNbO3), lithium tantalate (LiTaO3), and barium titanate (BaTiO3) can be piezoelectric, ferroelectric, and / or pyroelectric. Waveguides made of such high refractive index materials, such as LiNbO3 or LiTaO3, may develop substantial surface charges due to their piezoelectric, ferroelectric, and / or pyroelectric properties as they are prepared for the deposition of patternable materials (e.g., polymers, resists). Furthermore, the dispensed volumes of patternable materials (e.g., polymers, resists) using jet deposition techniques may also be charged. Under certain conditions, charged volumes of patternable materials (e.g., polymers, resists) may diffuse asymmetrically when dispensed onto a charged surface using jet deposition techniques. This can result in the dispensed volume deviating from the desired volume and / or causing undesirable fusion of different dispensed volumes. Therefore, in some embodiments, the patternable material (e.g., polymer, resist) may be deposited on the charged surface of the waveguide using other deposition techniques, e.g., coating, spin coating, spraying, or other pre-metering coating techniques, e.g., slot dies, doctor blades, knife edges, screens, etc. An exemplary method for patterning the waveguide 1001, consisting of a material with a high refractive index (e.g., refractive index of about 1.8 or higher), is shown. As shown in block (I), an uncured patternable layer 1011, consisting of the patternable material (e.g., polymer, resist) having a desired thickness, is deposited across the surface of the waveguide 1001. In various embodiments, an adhesion promoter layer 1003 may be deposited across the surface of the waveguide 1001 before the deposition of the uncured patternable layer 1011. The uncured patternable layer 1011 can be patterned using an imprint template 1007 having multiple imprint features and cured by irradiation with light such as ultraviolet (UV) light 1009, as shown in block (II) of Figure 10A. Alternatively, the imprinted patternable layer 1011 can also be cured by other methods such as heating.In this implementation, once the patternable layer 1011 is cured, the imprint template 1007 is removed, and the patterned layer 1005 can be obtained as shown in block (III) of Figure 10A. As discussed above, in some cases, for example, coating, spin coating, spraying, or other pre-metering coating techniques, such as slot dies, doctor blades, knife edges, and screens, may not be able to deposit different volumes of patternable material (e.g., polymers, resists) onto different parts of the waveguide surface, enabling the fabrication of diffraction features with variable height and / or pitch. Furthermore, the step of depositing patternable material (e.g., polymers, resists) using, for example, coating, spin coating, spraying, or other pre-metering coating techniques, such as slot dies, doctor blades, knife edges, and screens, may result in waste of patternable material.

[0770] Another method for fabricating patterned waveguides made of high refractive index materials exhibiting piezoelectric, ferroelectric, and / or pyroelectric behavior is illustrated in Figure 10B. In this method, one or more surfaces of waveguide 1001 made of high refractive index materials exhibiting piezoelectric, ferroelectric, and / or pyroelectric behavior are provided with a layer of dielectric material 1013 that facilitates the deposition of an uncured patternable layer 1011 using jet deposition techniques, as shown in block I(a) of Figure 10B (e.g., deposited thereon, coated, etc.). Optionally, the layer of dielectric material 1013 can be placed on / over one or more surfaces of the waveguide. In some implementations, the layer of dielectric material 1013 can have a thickness of approximately 5 nm to approximately 200 nm. The dielectric material can be transparent to visible wavelengths of light. In some implementations, the dielectric material can have a refractive index substantially similar to that of the high refractive index material of the waveguide. For example, the difference between the refractive index of the dielectric material and the high refractive index material of the waveguide can be about 20% or less in some implementations. However, it is also conceivable that the difference between the refractive index of the dielectric material and the high refractive index material of the waveguide can exceed about 20% in some implementations. In various embodiments, the dielectric material layer 1013 can consist of silicon carbide (SiC), titanium dioxide (TiO2), zirconium dioxide (ZrO2), silicon nitride (Si3N4), or silicon dioxide (SiO2). In some embodiments, the dielectric material can be disposed across one or more surfaces of the waveguide, consisting of a high refractive index material exhibiting piezoelectric, ferroelectric, and / or pyroelectric behavior, using, for example, a physical deposition process such as sputtering or evaporation. In some embodiments, the dielectric material can be distributed across one or more surfaces of a waveguide, consisting of a high refractive index material exhibiting piezoelectric, ferroelectric, and / or pyroelectric behavior, using chemical vapor deposition (CVD) processes such as plasma-enhanced chemical vapor deposition (PECVD), atmospheric pressure plasma-enhanced chemical vapor deposition (APPECVD), or atomic layer deposition (ALD). The use of other approaches may also be considered as possibilities.

[0771] The dielectric material layer 1013 can consist of a material that does not exhibit piezoelectric, ferroelectric, and / or pyroelectric behavior. Therefore, the surface of the dielectric material layer 1013 cannot accumulate charge in various implementations, for example, as the waveguide 1001 is placed on the chuck of a lithography tool or moved relative to the print head of a jet deposition device. Consequently, the dispensed volumes of patternable material (e.g., polymer, resist) deposited on the surface of the dielectric material using jet deposition techniques may not diffuse asymmetrically or fuse with adjacent volumes in some implementations, as shown in block I(a) of Figure 10B. For example, droplets may fuse beforehand instead of remaining at the droplet location where they are dispensed. Therefore, the predefined spacing between dispensed droplets required to achieve a controlled residual layer thickness (RLT) of the patterned layer cannot be maintained. If the dispensed droplets are pre-fused prior to being imprinted by the template, the thickness of the RLT can be random and uncontrolled. The resulting pattern obtained after imprinting and curing may have variable thickness and / or other non-uniformity. Such variations and non-uniformity in thickness may not be reproducible and may cause distortion in the virtual image. For example, the sharpness, contrast, uniformity, and / or brightness of the virtual image may be reduced in some embodiments. The uncured patternable material can also be deposited using deposition techniques such as jet deposition, coating, spin coating, spraying, or other pre-metering coating techniques, e.g., slot dies, doctor blades, knife edges, screens, etc., as shown in block I(b) of Figure 10B. The dispensed volume of patternable material 1011 or uncured patternable layer 1011 can be patterned by bringing an imprint template 1007 with an imprint pattern into contact with the dispensed volume of patternable material 1011 or uncured patternable layer 1011, as shown in Block II of Figure 10B. As discussed above, this imprinting process may be referred to as contact imprint lithography.The imprint template may have nanoscale or microscale features. The features of the imprint template can have variable height, depth, pitch, shape, arrangement, and / or location of the imprint features, or any combination thereof. In some other embodiments, the dispensed volume of the patternable material 1011 or the uncured patternable layer 1011 can also be patterned by other lithography techniques. The patterned material can be cured by light 1009, such as from an ultraviolet (UV) source, and / or by heating, as shown, for example, in block (II) of Figure 10B. The imprint template can be removed after the patterned material has been cured and a patterned layer 1005 has been obtained, as shown in block (III) of Figure 10B. Thus, the patternable material is patterned and forms a patterned layer 1005.

[0772] In some embodiments, the patterned layer 1005 can be used as an etching mask to etch a waveguide made of a high refractive index material. In some embodiments, the etching process can be configured to etch through a layer of dielectric material 1013 and the surface of the waveguide 1001 made of the high refractive index material. In various embodiments, the patterned layer of dielectric material can be removed using different wet or dry etching processes after the waveguide 1001 made of the high refractive index material has been etched. However, in some embodiments, the patterned layer of dielectric material can be left so that the patterned surface of the waveguide 1001 includes the patterned layer of dielectric material. In various embodiments, the patterned surface of the waveguide 1001 can be provided with a layer of material, a film of material, a coating of material, or a nanoarchitecture configured to reduce ambient light and optical artifacts in the user's field of view. For example, in some embodiments, an anti-reflective (AR) coating can be used to reduce ambient light and optical artifacts in the user's field of view. In some implementations, a coating consisting of titania (TiO2), silica (SiO2), magnesium fluoride (MgF2), or alternating layers thereof can be used to reduce ambient light and optical artifacts in the user's field of view. In some embodiments, the waveguide 1001 may be colored to reduce ambient light and optical artifacts in the user's field of view. In some embodiments, optical elements that provide additional functions (e.g., focusing, diverging, collecting light) can be integrated with the patterned surface of the waveguide. For example, a Fresnel lens or a plano-convex lens may be arranged across the patterned waveguide 1001, as discussed below with reference to Figure 27.

[0773] Another method for fabricating a patterned waveguide made of a high refractive index material exhibiting piezoelectric, ferroelectric, and / or pyroelectric behavior is depicted in Figure 10C. This method includes the step of providing an adhesion promoter layer 1003 over one or more surfaces of a waveguide 1001 made of a high refractive index material exhibiting piezoelectric, ferroelectric, and / or pyroelectric behavior, as shown in block I(b) of Figure 10C. In some embodiments, the adhesion promoter layer may consist of 2-[(trimethylsilyl)oxy)ethyl acrylate. The adhesion promoter layer can be placed on the surface of the waveguide, for example, by spin coating or by a physical or chemical vapor deposition method. The patterned layer can be placed over the adhesion promoter layer using a template coating pattern transfer method. The template coating pattern transfer method includes the step of placing an uncured patternable material 1011 (e.g., polymer or resist) onto an imprint template 1007 having an imprint pattern, as shown in block I(a) of Figure 10C. An uncured patternable material 1011 (e.g., a polymer or resist) can be placed across the patterned surface of an imprint template 1007 using jet deposition techniques, or other deposition methods such as coating, spin coating, spraying, or other pre-metering coating techniques, e.g., slot dies, doctor blades, knife edges, screens. The imprint pattern may have nanoscale or microscale features. Once the uncured patternable material 1011 (e.g., a polymer or resist) is placed across the patterned surface of the imprint template 1007 using jet deposition techniques, the droplet pattern may be designed so that dispensed polymer droplets diffuse across the patterned surface as a result of capillary action, as shown in block I(a) of Figure 10C.The patterned surface of an imprint template 1007, comprising an uncured patternable material 1011 (e.g., polymer or resist) dispensed, is brought into contact with the surface of a waveguide 1001, which is coated with an adhesion promoter layer, as shown in block II of Figure 10C, and cured using light such as UV illumination 1009. In some embodiments, the patternable material can be cured using thermocuring. During the curing process, the patternable material 1011 (e.g., polymer or resist) is transferred from the template 1007 to the adhesion promoter layer 1003. The template 1007 is removed once the patterned patternable material (e.g., polymer or resist) has been transferred to the surface of the waveguide 1001 and the waveguide 1001, comprising a patterned layer 1005, is obtained, as shown in block (III) of Figure 10C. As discussed above, in some embodiments, the patterned layer 1005 can be used as an etching mask to etch the surface of the waveguide 1001, which is made of a high refractive index material. In some embodiments, the etching process may be configured to etch into the surface of the waveguide 1001, which is made of a high refractive index material, through an adhesion promoter layer 1003. In various embodiments, the adhesion promoter layer 1003 may be removed after the waveguide 1001, which is made of a high refractive index material, has been etched. As discussed above, in various embodiments, the patterned surface of the waveguide 1001 may be provided with a layer of material, a film of material, a coating of material, or a nanoarchitecture configured to reduce ambient light and optical artifacts in the user's field of view. For example, in some embodiments, an anti-reflective (AR) coating may be used to reduce ambient light and optical artifacts in the user's field of view. In some implementations, a coating consisting of titania (TiO2), silica (SiO2), magnesium fluoride (MgF2), or an alternating layer thereof may be used to reduce ambient light and optical artifacts in the user's field of view. In some embodiments, the waveguide 1001 may be colored to reduce ambient light and optical artifacts in the user's field of view.In some embodiments, optical elements that provide additional functions (e.g., focusing, diverging, or collecting light) can be integrated with the patterned surface of the waveguide.

[0774] In some embodiments, it may be desirable to dissipate surface charges that may arise on various waveguides made of high refractive index materials exhibiting piezoelectric, ferroelectric, and / or pyroelectric behavior. In some embodiments, charges on one or more surfaces of the waveguide can be reduced or dissipated by using an ionizer that can neutralize the charges on one or more surfaces of the waveguide using bipolar clean air ionization or negative or positive ion-rich gas, depending on the surface charges generated. For example, ions provided through ionization can be directed towards the waveguide and reduce the charge on it. In some embodiments, charges on one or more surfaces of the waveguide can be reduced or dissipated using plasma. In some embodiments, a secondary charged or grounded surface can be brought into close proximity with one or more surfaces of the waveguide to dissipate surface charges generated on one or more surfaces of the waveguide. In some embodiments, a secondary charged surface can be brought into close proximity with one or more surfaces of the waveguide as the waveguide and / or printheads of jet deposition technology move relative to each other. In some embodiments, the waveguide can be electrically contacted with a grounded chuck, which may help dissipate charge accumulation on one or more surfaces of the waveguide. In some embodiments, a metallic coating (e.g., iridium (Ir), chromium (Cr), or nickel (Ni) coating) or other conductive coating can be placed over at least a portion of one or more charged surfaces of the waveguide to dissipate surface charge. While not endorsed by any particular theory, the metallic coating can act as a conductive film to dissipate surface charge accumulation, for example, uniformly. In some embodiments, a conductive oxide (e.g., a transparent conductive oxide such as indium tin oxide (ITO)) can be placed over at least a portion of the waveguide surface to dissipate surface charge that may accumulate on one or more surfaces of the waveguide. Other conductive films and other methods of discharge or charge dissipation may be used.

[0775] In some implementations, depending on the dissipation of surface charge in the manner discussed above, the patternable material can be dispensed using jet deposition techniques and patterned using an imprint template, as discussed above. The patterned patternable material can be cured using UV curing, thermal curing, or other curing processes. In some embodiments, the patterned patternable material can be etched and used to pattern one or more surfaces of a waveguide made of a high refractive index material. In embodiments of the manufacturing method that employ the step of dissipating surface charge by placing a conductive coating, such as a metallic coating, over one or more surfaces of the waveguide, the patternable material can be dispensed over the conductive or metallic coating and patterned using an imprint template, as discussed above. In some embodiments, both the patterned patternable material and the conductive or metallic layer can be used as an etching mask and etched into one or more surfaces of the waveguide.

[0776] In some embodiments, charge buildup on the waveguide surface can be reduced before the deposition of the patternable material, in order to facilitate the deposition of patternable material onto the charged surface of the waveguide, which is made of a high refractive index material exhibiting piezoelectric, ferroelectric, and / or pyroelectric behavior. For example, hydrothermal stress / strain on the waveguide can be reduced during cleaning of the waveguide surface prior to the deposition of the patternable material and / or other processes undertaken to prepare the waveguide surface for patternable material deposition. In various embodiments, charge dissipation and surface cleaning can be performed together by exposing the surface of the LiNbO3 wafer to a plasma. For example, atmospheric pressure plasma can be used to dissipate surface charge and clean the surface. In some implementations, the plasma can be at a temperature of about 20–50 degrees Celsius. In this temperature range, the plasma can consist of argon (Ar) and oxygen (O) ions and radicals. Furthermore, it is desirable to avoid large temperature fluctuations between different processes during the processing of a lattice structure onto a waveguide, for example, made of a high refractive index material such as LiNbO3. For example, if the temperature fluctuation between different processes during the processing of a lattice structure onto a waveguide, made of a high refractive index material such as LiNbO3, exceeds approximately 30 degrees Celsius, the risk of cracking of the waveguide substrate (e.g., wafer) increases. Cracks in the waveguide substrate (e.g., wafer) can degrade the surface of the waveguide. In some cases, for example, debris from cracks can contaminate the surface of the waveguide. In some embodiments, it may be desirable to reduce mechanical stress / strain on the waveguide during handling and placement on the chuck prior to the deposition of the patternable material. Chuck designs, including but not limited to cavity chucks, grounded chucks, and / or chucks configured to reduce surface charge accumulation on the waveguide surface, may be advantageously employed. For example, non-contact imprint chucks, such as hollow chucks, can be used to reduce mechanical stress on the waveguide and / or to reduce or avoid scratches on the waveguide surface.In another embodiment, a chuck having a flexible chuck design can be used to support the waveguide during polymer deposition. A benefit of the flexible chuck design is that, during contact-based imprinting, the load can be transferred from the imprint template to the chuck system instead of being transferred to the waveguide. Another embodiment for reducing charge accumulation on the waveguide surface before deposition of patternable material may include a step in contact-based imprint lithography to reduce the mechanical stress generated during polymer curing (e.g., UV curing or thermal curing). This can be accomplished by releasing the mechanical constraints on the waveguide from the chuck during curing (e.g., releasing the vacuum held on the waveguide), and then reapplying them after the patternable material has cured, for other processes such as template separation. Thus, in various implementations, charge accumulation can be reduced by releasing or applying mechanical pressure on the waveguide.

[0777] Not all high refractive index materials exhibiting piezoelectric, ferroelectric, and / or pyroelectric behavior are afflicted with the surface charge accumulation problem discussed above. For example, volumes of patternable material can be dispensed onto the surface of a waveguide consisting of silicon carbide, Z-cut, X-cut, or Y-cut LiNbO3 using jet deposition techniques without the risk of undesirable diffusion of the patternable material or fusion of adjacent volumes. Therefore, it may not be necessary to provide additional layers, coatings, or films (e.g., conductive layers such as metals or conductive oxides) on the surface of such a waveguide before dispensing the patternable material using jet deposition techniques. It may also not be necessary to dissipate surface charge using the various techniques described above before dispensing the patternable material using jet deposition techniques in such waveguides. In various implementations, it may be advantageous to place one or more layers on the surface of the waveguide to make the intermediate layer or surface scratch-resistant and / or low-reflectivity, for example, an adhesion-enhancing material to promote adhesion. The intermediate adhesion-promoting material may include SiC with a refractive index of about 2.6–3.0, TiO2 with a refractive index of about 2.3, or silicon dioxide with a refractive index of about 1.45. In some implementations, the intermediate functional layer may be configured to have a high surface energy, which, when deposited using jet deposition techniques, can introduce desirable diffusion of the material (e.g., polymer). In some implementations, the diffusion behavior of the dispensed patternable material can be used to improve the rapid and controlled pre-diffusion of the patternable material (e.g., resist solution) for nanoscale patterning. In some embodiments, the patternable material may be configured not to diffuse across the surface of the adhesion-promoting layer. This property may be advantageous for avoiding or reducing evaporation of the patternable material during the patterning process. Therefore, for example, in various embodiments, the adhesion-promoting material or other intermediate layer may have certain functional groups that make the layer of adhesion-promoting material or other intermediate layer hydrophobic so that the dispensed patternable material beads up, or hydrophilic so that the dispensed patternable material diffuses.Thus, the surface energy of the adhesion-enhancing layer or other intermediate layer can be adjusted to control the amount of droplet diffusion. The adhesion-enhancing layer or other intermediate layer can act as a site for bonding to cured polymers and / or uncured polymers. In some embodiments, the adhesion-enhancing layer or other intermediate layer can be deposited across a waveguide made of a higher refractive index material by spin coating, microgravure printing, dipping coating, or atomization (spraying) followed by a drying step (e.g., heat-assisted drying). Other deposition methods may also be used. In some embodiments, the adhesion-enhancing layer or other intermediate layer can be deposited across a waveguide made of a higher refractive index material by vapor deposition using an inert carrier gas such as nitrogen (N2), argon (Ar), or helium (He). In some embodiments, vapor deposition can be carried out in the presence of water, which can facilitate bridging between the adhesion-enhancing layer and the waveguide made of the high refractive index material. The layer of adhesion-enhancing material or other intermediate layer may have a thickness of 10 nm or less in some implementations. For example, the thickness of the adhesion-promoting material layer or other intermediate layer can be approximately 0.5 nm or more and approximately 1 nm or less, 0.5 nm or more and 1.5 nm or less, 1.0 nm or more and 3.0 nm or less, 1.8 nm or more and 4.0 nm or less, 3.0 nm or more and 5.0 nm or less, 4.0 nm or more and 6.0 nm or less, 5.0 nm or more and 7.5 nm or less, 7.5 nm or more and 10.0 nm or less, 10 nm or more and 20.0 nm or less, 20 nm or more and 40.0 nm or less, or any value within any range / sub-range defined by these values.

[0778] Waveguides made of high refractive index material (e.g., refractive index above about 1.8) with a patterned surface can be used in display devices to provide a wider field of view compared to patterned waveguides made of glass or material with a refractive index below 1.8 (e.g., sapphire (Al2O3) with a refractive index of about 1.76). For example, such a waveguide can be incorporated into the eyepiece of a head-mounted display to direct light into the eye and form an image therein. Furthermore, a single patterned waveguide made of high refractive index material (e.g., refractive index above about 1.8) can be used to internally couple two or more (e.g., two or three) different colors or wavelengths of light (e.g., green and blue light) output from an optical source (e.g., a projection device) and project two or more (e.g., two or three) different colors or wavelengths of light toward the viewer.

[0779] Figure 10D shows an implementation of a waveguide 1001 made of a high refractive index material, such as LiNbO3, which is fabricated using the various methods discussed above. A patterned layer 1005 is placed across the surface of the waveguide 1001. The patterned layer 1005 can be made of a patternable material that can be patterned by contact imprint lithography, optical lithography, or other lithography methods. For example, the patterned layer 1005 can be made of a polymer such as a resist or photoresist. The patterned layer 1005 can be made of a material having a refractive index less than that of the waveguide 1001. For example, the patterned layer 1005 can have a refractive index less than 1.8 (e.g., refractive index about 1.2 to 1.7). The patterned layer 1005 can have multiple diffraction features 1007. The thickness of the patterned layer 1005 can be less than 20 nm in some implementations. Multiple diffraction features 1007 can be configured to diffract both blue and green light through the waveguide 1001. In some such embodiments, a second waveguide made of a material with a high refractive index, with a second patterned layer having multiple diffraction features configured to diffract red light, can be used to project a red image out of the second waveguide. In some embodiments, multiple diffraction features 1007 can be configured to diffract red, green, and blue light so that virtual red, green, and blue images of an object can be projected out of the waveguide 1001. II. Direct Patterning of Waveguides with High Refractive Index Materials

[0780] Another method for fabricating a patterned surface on a waveguide made of a high refractive index material (e.g., SiC, LiNbO3, or other optically transparent material having a refractive index of 1.8 or greater) may include the step of directly patterning one or more surfaces of the waveguide made of the high refractive index material. This step of directly patterning one or more surfaces of the waveguide made of the high refractive index material can be carried out by using etching techniques, such as dry reactive ion etching (RIE), inductively coupled plasma (ICP) etching, or ion beam etching.

[0781] The step of directly patterning one or more surfaces of a waveguide made of a high refractive index material includes the step of placing an etching mask having a pattern over the waveguide surface to be patterned. The pattern of the etching mask can be a positive pattern corresponding to a pattern to be etched on the waveguide surface, or a negative pattern corresponding to a pattern opposite to a pattern to be etched on the waveguide surface. Using appropriate etching techniques and appropriate etching chemistry, the waveguide surface can be etched through the etching mask.

[0782] In some embodiments, a patterned polymer, which is placed across the surface of a waveguide using optical lithography or contact imprint lithography as described above, can be used as an etching mask. The pattern of the patterned polymer is transferred onto the surface of the waveguide substrate using a different etching process (e.g., dry etching). Figures 11A–11D illustrate different methods of directly patterning the surface of a waveguide made of a high refractive index material using an etching mask, as discussed above.

[0783] Figure 11A illustrates a method for directly patterning a waveguide 1101 made of, for example, LiNbO3, using an etching mask 1103a. The etching mask 1103a may consist of a patterned patternable material (e.g., a polymer acrylate-based resist). For example, the etching mask 1103a may comprise a patterned layer 1005 as described above. In such embodiments, the etching mask 1103a may consist of a polymer or resist material. For example, the etching mask 1103a may consist of a polymer acrylate-based resist. The etching mask 1103a has a base 1104a having a certain height and a plurality of features 1105a extending above the base 1104a. In various embodiments, the height of the base 1104a may be about 5 nm to 60 nm, but different thicknesses outside this range may also be used. The waveguide 1101 and etching mask 1103a, made of LiNbO3, can be etched using dry etching or ICP with one or more of the following gases: CBrF3, HBr, CHF3, CF4, C4F8, CH4, SF6, He, H2, Ar, and O2. The etching conditions (e.g., etching time and other etching parameters) can be controlled so that the base 1104a of the etching mask is completely etched, exposing a portion of the waveguide 1101 made of LiNbO3. The height of the multiple features 1105a of the etching mask 1103b from the surface of the waveguide 1101, on which they are placed, can be reduced, but the multiple features 1105a are reserved. A second etching using the chemical properties of F, Br, Ar, and CH is used to etch through the exposed portion of the waveguide 1101 made of LiNbO3 and the remaining portion of the multiple features 1105a. If the remaining portion of the multiple features 1105a consists of a polymer acrylate-based resist, they can be etched at a rate approximately three times higher than the rate at which the exposed portion of the waveguide 1101 is etched by the second etching process. Therefore, the height of the multiple features 1106a fabricated on the surface of the waveguide 1101 can be small.In embodiments of a display device comprising a waveguide 1101 in which a plurality of features 1106a formed within the waveguide 1101 are configured as internal coupling optical elements, external coupling optical elements, or optical dispersion elements, the efficiency of optical internal coupling, optical external coupling, and / or optical distribution may be reduced if the height of the plurality of features 1106a is small. To increase the height of the plurality of features 1106a, the etching mask may consist of a material having a different composition from "polymer resist: LiNbO3" that can be etched at a rate comparable to the etching rate of the waveguide material 1101. For example, in some embodiments, the etching mask 1103a may consist of a resist made of some silicon (Si), such as about 1% to about 25% by weight of silicon. Adding silicon to the resist can reduce the etching rate of the etching mask 1103a and, as a result of the reduction in the etching rate, can increase the etching selectivity. For example, adding silicon to certain parts of the resist can reduce the etching rate in those parts of the resist. Therefore, the control of the etching depth can be improved in those parts of the resist. Various physical and chemical components of RIE etching can be changed in various implementations to modify the etching rate and increase or decrease the etching selectivity. Similarly, the etching rate of the etching mask 1103a may depend on the etching chemical properties. Etching chemical properties that reduce the etching rate of the etching mask compared to the waveguide may be used to reduce the etching rate of the mask without reducing the etching rate of the waveguide, or without reducing the etching rate of the waveguide as much. In some embodiments, the height of multiple features 1106a may depend on the height of the pattern of the etching mask 1103a. Therefore, in various embodiments, the height of multiple features 1106a in the waveguide can be adjusted by selecting the height of the pattern of the etching mask 1103a, the polymer composition, and / or the etching chemical properties.

[0784] Figure 11B illustrates a method for directly patterning a waveguide 1101 made of LiNbO3 using an etching mask 1103b. The etching mask 1103b may consist of an imprint resist comprising a certain amount of silicon. As discussed above, the addition of silicon to the patternable material can reduce the etching rate of the etching mask 1103b and increase its etching selectivity. A general class of imprint resists comprising silicon is described in U.S. Patent No. 7,282,550 (which is incorporated herein by reference as a whole). The composition of the etching mask 1103b may be analogous to compositions 1, 2, 3, 4, 5, 6, 7, and 8 described in U.S. Patent No. 7,282,550 (which is incorporated herein by reference as a whole). The etching mask 1103b has a base 1104b and a plurality of features 1105b extending above the base 1104b. When the organo-silicon bond of an imprint resist made of silicon is exposed to oxygen during the RIE etching process, inorganic SiO xIt can be converted to form a mask. The waveguide 1101 made of LiNbO3 and the etching mask 1103b can be etched using a first etching process based on the chemical properties of F, CH, Ar, O, which completely etches the base 1104b of the etching mask 1103b and the exposed portion of the waveguide 1101 made of LiNbO3. The height of multiple features 1105b on the etching mask from the surface of the waveguide 1101, on which they are placed, is reduced, but multiple features 1105b are reserved. A second etching using the chemical properties of F, Br, Ar, CH is used to etch through the exposed portion of the waveguide 1101 made of LiNbO3 and the remaining portion of the multiple features 1105b. The etching rate of a patternable material (e.g., resist) made of silicon is lower than the etching rate of the patternable material (e.g., resist) alone. Similarly, the etching selectivity of a resist made of silicon is higher than the etching selectivity of the resist alone. Therefore, the height of the multiple features 1106b processed on the surface of the waveguide 1101, as shown in Figure 11B, can exceed the height of the multiple features 1106a processed on the surface of the waveguide 1101, as shown in Figure 11A. Similarly, the height of the multiple features 1106b within the waveguide can be increased by slowing down the etching rate of the patternable material constituting the etching mask 1105b and matching it to more closely approximate the etching rate of the waveguide 1101.

[0785] Figure 11C illustrates a method for directly patterning a waveguide 1101 made of LiNbO3 using an etching mask 1103c. The etching mask 1103c has a base 1104c having a certain height and a number of features 1105c extending above the base 1104c. The etching mask 1103c can be an imprint resist having a certain amount of silicon. The etching mask 1103c is placed on a transfer layer such as an organic transfer layer 1107c. The organic transfer layer 1107c can consist of a material such as another acrylate or epoxy-based polymer. The transfer layer (e.g., organic transfer layer) 1107c can be deposited over the surface of the waveguide 1101 using a deposition technique, including but not limited to coating, spin coating, spraying, or other pre-metering coating techniques, such as slot dies, doctor blades, knife edges, screens, etc. The thickness of the transfer layer 1107c can be about tens to hundreds of nanometers (nm) in some implementations. The direct patterning process uses fluorine chemical properties, undergoes descam treatment, then switches to Ar / O2, and SiO xThe process may include constructing a mask and then etching the exposed portion of the waveguide 1101 through the etching mask 1103c and transfer layer (e.g., organic transfer layer) 1107c using the chemical properties of F, CH, Ar, O, and He. A portion of the etching mask 1103c and transfer layer 1107c is still reserved. Subsequently, the exposed portion of the waveguide 1101 and the remaining portions of the etching mask 1103c and transfer layer (e.g., organic transfer layer) 1107c can be etched using the chemical properties of F, Br, Ar, and CH to form multiple features 1106c. While not endorsed by any particular theory, there may be limits to the height of the resist layer that can be imprinted using contact imprint lithography without encountering defects such as nano-feature shear, line sidewall inclination, and line contact / fusion. In some implementations, imprint features (also referred to as height features) that have a height exceeding a threshold height, obtained through contact-based imprinting using an imprint template with similar or equal height features, can reduce pattern fidelity. Therefore, the organic transfer layer 1107c can be used to create an etching mask with height features obtained through contact-based imprinting using an imprint template with features having a height less than the height of the etching mask features. This may be useful to obtain a higher etching mask when it is required to overcome certain process constraints in imprint patterning.

[0786] Figure 11D illustrates a method for directly patterning a waveguide 1101 made of LiNbO3 using an etching mask 1103d. The etching mask 1103d is formed by depositing a transfer layer (e.g., an organic transfer layer) 1107d onto the surface of the waveguide 1101. As discussed above, the organic transfer layer 1107d can be made of a material such as Transpin or BARC. The transfer layer 1107d can be deposited using jet deposition techniques, or, but is not limited to, coating, spin coating, spraying, or other pre-metering coating techniques, including slot dies, doctor blades, knife edges, screens, etc. The thickness of the transfer layer 1107d can be about tens to hundreds of nanometers (nm) in some implementations. The transfer layer 1107d can be structurally and functionally similar to the transfer layer 1107c. The transfer layer 1107d can be patterned using a lithography technique such as contact imprint lithography. The patterned transfer layer 1107d may have multiple features 1105d. An etching layer 1108d may be deposited over the imprinted transfer layer 1107d and planarized using a planarization template. The etching layer 1108d may consist of silicon, for example, SilSpin. This process may be referred to as jet and flash imprint lithography reversal stone (J-FIL-R). A portion of layer 1108d that spans multiple features 1105d of the patterned transfer layer 1107d can be removed by etching, resulting in the structure shown at the top of Figure 11D. For example, the chemical properties -F, -CH, Ar, and -O can be used to remove a portion of layer 1108d that spans multiple features 1105d of the patterned organic transfer layer 1107d. Subsequently, the exposed portion of the transfer layer 1107d can be etched downward to the waveguide. For example, the chemical property Ar / O2 can be used, for example, SiO xIt can be used to remove a transfer layer (e.g., an organic transfer layer) while oxidizing a portion of the etching layer 1108d, which may consist of Si, in order to form an etching mask. Subsequently, the exposed portion of the waveguide 1101 and the oxidized SiO x The mask and the remaining portion of the organic transfer layer 1107d can be etched using -F, -Br, Ar, and -CH chemical properties to form multiple features 1106d within the waveguide. This approach has the advantage of using the composition of an organic resist for imprinting. Organic resists can be mechanically stronger than Si resists. Therefore, defects in the imprint process can be reduced. III. Etching into a high-refractive-index coating placed across the surface of a waveguide containing a high-refractive-index material.

[0787] Various embodiments of waveguides made of high refractive index materials can be patterned by depositing a layer of such high refractive index material (n>1.8) with a low absorption coefficient (k<0.001) having a high refractive index over the surface of the waveguide, depositing a patternable layer (e.g., a resist layer) over a layer of dielectric material, patterning the patternable layer (e.g., a resist layer), etching the deposited layer of high refractive index material, and obtaining a patterned layer of dielectric material. In various embodiments, the deposited material, i.e., the layer of high refractive index material, can consist of SiC, TiO2, ZrO2, or Si3N4. In some embodiments, the refractive index of the deposited material can be substantially similar to that of the waveguide material. For example, in some implementations, the difference in refractive index between the deposited material and the waveguide material can be less than about 20%. However, in some embodiments, the difference in refractive index between the deposited material and the waveguide material can be about 20% or more. In some embodiments, the refractive index of the dielectric material can exceed that of the waveguide material. A deposited material with a high refractive index can be selected based on the desired height / depth of the features to be etched and the etching chemical properties used for etching. For example, a TiO2 layer etches faster than LiNbO3 with respect to certain etching chemicals. Therefore, if the waveguide is made of LiNbO3, the waveguide surface can act as an etching stop layer with respect to those etching chemicals, since TiO2 etches faster than LiNbO3. The resulting product can be a waveguide with diffracting features consisting of dielectric or dielectric portions of the waveguide material. IV. Use of multiple mask layers for etching inside a waveguide

[0788] For example, various embodiments of waveguides made of high refractive index materials such as LiNbO3, LiTaO3, or SiC can be patterned by using multiple masks. One or more of the multiple masks can be etched using etching chemistry different from that used to etch the waveguide material. For example, an embodiment of a method for patterning a waveguide made of a high refractive index material such as LiNbO3, LiTaO3, or SiC includes the step of arranging a layer of material that can be etched using etching chemistry different from that used to etch the waveguide material. For example, if the waveguide is made of TiO2, a layer made of chromium (Cr) or nickel (Ni) is deposited over the surface of the waveguide to be etched. The layer made of chromium (Cr) or nickel (Ni) can be deposited using deposition techniques such as sputtering or evaporation. In some embodiments, layers made of chromium (Cr) or nickel (Ni) can be deposited under low-pressure plasma conditions in an oxygen-rich environment, with or without the use of high temperatures, and then oxidized under an accelerated oxidation process. Layers made of chromium (Cr), nickel (Ni), or their oxides Cr2O3, NiO can be etched using chlorine-based chemistry, while waveguides made of TiO2 can be etched using fluorine-based chemistry. Layers made of chromium (Cr), nickel (Ni), or their oxides Cr2O3, NiO can be patterned to form a first etching mask. Portions of the TiO2 waveguide not covered by the first etching mask can be etched using fluorine-based chemistry. After processing the features on the waveguide surface, the first etching mask can be etched using chlorine-based chemistry.

[0789] One method for patterning layers consisting of chromium (Cr), nickel (Ni), or their oxides, e.g., Cr2O3, NiO, involves the step of depositing a layer of silicon dioxide (SiO2) over a layer consisting of chromium (Cr), nickel (Ni), or their oxides, Cr2O3, NiO. A layer of polymer (e.g., SiO2: resist polymer) that can be imprinted is placed over the SiO2 layer using various deposition techniques, e.g., jet deposition or spin coating. The polymer layer can be imprinted using an imprint template or by photolithography. The SiO2 layer can be etched using the -F, -CH, Ar, and O chemical properties to form a patterned SiO2 layer. A layer consisting of chromium (Cr), nickel (Ni), or their oxides is then etched using the -Cl, Ar, and O chemical properties to form a patterned layer consisting of chromium (Cr), nickel (Ni), or their oxides.

[0790] Therefore, the waveguide can be etched by depositing a first etching mask, which may consist of a metal or an oxidized metal. A second etching mask may be deposited over layers of the material constituting the first etching mask, patterning the first etching mask from the layers of material used to form the first etching mask. The second etching mask may consist of an oxide such as SiO2. Possibly, a third etching mask, consisting of a polymer, may be used to etch and pattern the second etching mask from layers of material consisting of the second etching mask material. Different etching chemicals may be employed to etch different etching mask layers. More or fewer layers may also be used. V. Stepwise etching

[0791] Stepwise etching techniques can be useful for processing diffraction features across the waveguide surface, involving stepwise alteration of the pitch and / or height of the diffraction features. Stepwise alteration of the pitch and / or height of diffraction features across the waveguide surface can be advantageous, for example, in increasing the uniformity and intensity of light output from the waveguide. For instance, diffraction features in regions of the waveguide with higher light intensity can be made shorter to reduce diffraction efficiency, while diffraction features in regions of the waveguide with lower light intensity can be made taller to increase diffraction efficiency. Thus, the uniformity of light output from the waveguide can be increased while maintaining the intensity of the light output. Several stepwise etching techniques are described below. A. Use of stepped polymer layers

[0792] One method for fabricating a waveguide having features with variable height traversing the waveguide surface includes the step of placing a sloped or stepped patternable layer made of a patternable material (e.g., polymer, resist) across the waveguide surface, which is imprinted using an imprint template having features with constant height. The patternable layer is deposited so as to be sloped with respect to the waveguide surface. The patternable layer may consist of a resist material that can be imprinted using an imprint template. The slope of the patternable layer may be configured to correspond to a desired stepping in the height of the features. For example, the patternable layer may be sloped such that the height of the patternable layer is higher in the portion of the waveguide that will be etched to a shallower (e.g., not very deep) depth. Without loss of generality, the height of the patternable layer corresponds to the distance from the waveguide surface to the exposed surface of the patternable layer opposite the waveguide surface. The patternable layer that can be sloped can be configured to be used as a negative or positive mask, as discussed below with reference to Figures 12A, 12B-1, 12B-2, and 12C.

[0793] Jet deposition technology implemented by inkjet printing devices can be used to deposit inclined patternable layers. For example, the volume of the patternable layer dispensed from the printhead of the inkjet printing device can be varied across the surface of the waveguide. In various embodiments, the printhead of the inkjet printing device can be configured to dispense droplets having a size in the range of about 50 microns to about 150 microns. For example, the dispensed droplets can have sizes ranging from approximately 50 to 60 microns, 55 to 65 microns, 60 to 70 microns, 65 to 75 microns, 70 to 80 microns, 75 to 85 microns, 80 to 90 microns, 85 to 95 microns, 90 to 100 microns, 100 to 110 microns, 110 to 120 microns, 120 to 130 microns, 130 to 140 microns, 140 to 150 microns, or any range between these values. The volume of the dispensed droplets can vary as the print head of the inkjet printing device moves across the surface of the waveguide. For example, in some embodiments, the volume of patternable material (e.g., the volume of material in a droplet, based on the size and / or density of the droplet) can be varied as the printhead of an inkjet printing device moves across the surface of the waveguide, which becomes the patterned area, to deposit or dispense a variable volume of polymer patternable layer. As discussed above, the inclined patternable layer is patterned by contact with an imprint template having features with a constant height. Thus, the height of the features in the patterned inclined patternable layer varies across the surface of the waveguide.

[0794] Two different methods for fabricating stepwise diffraction features onto a waveguide surface using a patternable layer with a patterned tilt are described below. Figure 12A illustrates an exemplary embodiment of a patternable layer with a patterned tilt 1203 placed on the surface of a waveguide 1201. The waveguide 1201 may be made of a high refractive index material such as SiC or LiNbO3. The patternable layer with a patterned tilt 1205 comprises a tilted base 1204 and a plurality of features 1205. The distance between the exposed surface of the plurality of features 1205 and the surface of the waveguide 1201 varies across the waveguide surface. Variation in the distance 1209 between the exposed surface of the plurality of features 1205 and the surface of the waveguide 1201 may correspond to the tilt of the tilted base 1204.

[0795] In a first method for fabricating a waveguide with stepped features, a patterned patternable layer 1203 is used as a positive mask so that height variations in multiple features 1205 are transferred to the surface of the waveguide 1201. The first method for fabricating a waveguide with stepped features includes a first step in which a sloped base layer 1204 is etched to expose the surface of the waveguide 1201 between the multiple features 1205, as shown in Figure 12B-1. In various embodiments, an etching process that etches only the material of the polymer layer 1203 without etching the material of the waveguide 1201 may be used to etch the sloped base layer 1204. The heights of the multiple features 1205 shown in Figure 12B-1 may be reduced during the process of etching the sloped base layer 1204, although some of the multiple features 1205 may be retained with respect to at least the majority of the features. A first method for fabricating a waveguide with stepped features includes a second step of fabricating a waveguide having multiple features 1206, as shown in Figure 12B-2, by etching the reserved portions of multiple features 1205 and the exposed portions of the waveguide 1201. In this embodiment, short lattice features are formed as a result of over-etching. Over-etching refers to the etching of lattice features after the etching mask (e.g., patterned patternable layer 1203) has been completely etched during the etching process. This leaves the lattice features exposed to the etching material. The lattice thus loses height and width as the etching process progresses, with increasing rounding of the sidewalls and corners. The linewidth reduction and height reduction resulting from over-etching are advantageous for fabricating a stepped lattice structure having lattice features of different heights, arranged on a tilted surface, as shown in Figure 12B-2. A patterned waveguide 1201, fabricated using the first method described above, has a base 1207 and a slanted surface 1208 opposite the base. The slanted surface 1208 comprises a plurality of features 1206. The distance between the base 1207 and the exposed surface of the plurality of features 1206 varies across the surface of the waveguide, as can be seen in Figure 12B-2.

[0796] In a second method for fabricating a waveguide with stepped features, the patterned patternable layer 1203 is used as a negative mask to form grooves with variable depths within the surface of the waveguide 1201. The second method includes the step of etching the sloped base layer 1204 and multiple features 1205 using an etching process that etches the material of the patternable layer 1203 and the material of the waveguide 1201, as shown in Figure 12C. In the second method of fabrication, the surface of the waveguide 1201 is etched, and the depth varies with the variation in the height of the patternable layer 1203. For example, as shown in Figure 12C, the depth of etching the surface of the waveguide 1201 is deeper in parts of the surface of the waveguide 1201 where the height of the patternable layer is lower. The patterned waveguide 1201 depicted in Figure 12C comprises a base 1207 and a plurality of grooves 1210, the depth 1211 of the plurality of grooves varying across the surface of the waveguide.

[0797] The pitches of the multiple features 1206 and the multiple grooves 1210 are depicted as constant or nearly constant in the patterned waveguide embodiments illustrated in Figures 12B-2 and 12C, however, the pitch, height, and arrangement of the diffraction features within the waveguide may vary depending on the pattern used, in various embodiments of the waveguide having a stepped pattern. The height and arrangement also differ. B. Using a step-by-step imprint template

[0798] Another method for fabricating a waveguide having features with variable height across the waveguide surface includes the steps of: placing a patternable layer having a constant height across the waveguide surface; and imprinting the patternable layer having a constant height using an imprint template having inclined or stepped imprint features. The imprint template having stepped imprint features can be fabricated using lithography techniques. The patternable layer may consist of a resist material that can be imprinted using a stepped imprint template, such as the stepped imprint template 1320 illustrated in F. The stepped imprint template 1320 comprises a plurality of grooves 1330 with variable depth 1330.

[0799] Figures 13B-13D illustrate various steps for fabricating a waveguide with variable height features. As discussed above, the waveguide 1301 can be made of an optically transparent material with a refractive index greater than 1.8. In some embodiments, the waveguide 1301 can be made of SiO2, Si3N4, ZrO2, TiO2, etc., across a substrate made of, for example, LiTaO3, LiNbO3, SiC, etc. A first step may include forming a patternable layer 1303 across the surface of the waveguide 1301. The height of the patternable layer 1303 can be constant across the surface of the waveguide 1301. The patternable layer 1303 of constant height is imprinted using a stepped imprint template 1320. The imprint template 1320 includes a plurality of grooves or trenches with variable depth. In the embodiments shown, the grooves or trenches have a gradually decreasing depth. The resulting patterned patternable layer 1303, formed by imprinting a layer of patternable material using the imprint template 1320, is shown in Figure 13B. The patterned patternable layer 1303 comprises a base 1304 and a plurality of features 1306 as a result of being imprinted using the imprint template 1320. In the implementations shown in Figures 13A and 13B, grooves or trenches in the imprint template 1320, having variable depth, correspond to and produce the features 1306 in the patternable layer, which have variable height 1309. The height 1308 of the base 1304 from the surface of the waveguide 1301 is constant or nearly constant across the surface of the waveguide 1301. The height 1309 between the exposed surface of the plurality of features 1306 and the exposed surface of the base 1304 varies across the surface of the waveguide 1301.

[0800] In the first method, a stepped height pattern can be transferred to the surface of waveguide 1301 by etching through the surface of patternable layer 1303 and waveguide 1301, as shown in Figure 13D, to obtain a waveguide having a surface with multiple features 1310 with stepped heights. In some implementations, for example, the stepped height pattern can be etched onto the surface of waveguide 1301 using RIE, ICP, or atmospheric plasma (AP) etching processes. In some implementations, -F, Ar, O, and -CH chemical properties can be used to etch through the surface of patternable layer 1303 and waveguide 1301. Using this method, a stepped height pattern can be transferred to the surface of waveguide 1301 in a single step.

[0801] A second method for transferring a stepped height pattern to the surface of the waveguide 1301 comprises two steps. The first step includes etching the base 1304 of the patternable layer to the exposed portion of the surface of the waveguide 1301, as shown in Figure 13C. In one implementation, for example, the first step includes etching the base 1304 of the patternable layer using an RIE, ICP, or atmospheric plasma (AP) etching process with Ar, O chemical properties. The height 1309 of the multiple features 1306 can be reduced during the process of etching the base 1304. The second step includes etching the remaining portion of the multiple features 1306 and through the surface of the waveguide 1301. The second step may include etching the remaining portion of the multiple features 1306 and through the surface of the waveguide 1301 using an RIE, ICP, or atmospheric plasma (AP) etching process with F, Ar, O, CH chemical properties. The etching depth on the surface of the waveguide 1301 can vary depending on the etching chemical properties and the height of the feature size. For example, in various embodiments, the etching depth can be directly proportional to the height of the feature, such that the highest imprint feature can produce the deepest etching depth and the lowest imprint height can produce the minimum etching depth, as shown in Figure 13D. The height of the shortest feature can be further reduced due to over-etching. The pitch of the multiple features 1310 is depicted as constant or nearly constant in the patterned waveguide embodiment illustrated in Figure 13D, but the pitch, height, and arrangement of features within the waveguide can vary depending on the pattern in various embodiments of the waveguide with a stepped pattern. C. Use of a stepped duty cycle

[0802] In various methods for etching the surface of a waveguide, the etching depth may depend on the area of ​​the waveguide surface exposed to the etching solution. Therefore, waveguide surfaces with multiple features of different heights can be obtained by varying the area of ​​the waveguide surface exposed to the etching solution. Figure 14 illustrates a method for fabricating a waveguide with a stepped height pattern. This method includes the step of depositing a patternable layer 1403 over the surface of the waveguide 1401. The waveguide can be made of a material with a refractive index of 1.8 or greater. The polymer layer 1403 can have multiple features with a variable pitch such that the gaps 1405 between the continuous features of the polymer layer 1403 vary across the surface of the waveguide, as shown in Figure 14A. Due to the dependence of the etching rate on the exposed surface area of ​​the waveguide 1401, features of different heights will be etched on the surface of the waveguide 1401. For example, the height of a feature formed within the surface portion of the waveguide 1401 corresponding to the portion of the patternable layer 1403 associated with a smaller gap between continuous features will be less than the height of a feature formed within the surface portion of the waveguide 1401 corresponding to the portion of the patternable layer 1403 associated with a larger gap between continuous features, as shown in Figure 14B. D. Use of resist materials with different compositions

[0803] Another method for fabricating waveguides with stepped height patterns involves depositing patternable materials (e.g., polymers, resists) of at least two different compositions onto different portions of the waveguide surface. The patternable materials of at least two different compositions have different etching rates when exposed to the same etching solution. Therefore, the different portions of the waveguide surface will have features of different sizes depending on the etching rates of the corresponding patternable materials (e.g., resists). Thus, waveguides with multiple features of different heights can be fabricated using a single etching process. Jet deposition techniques may be advantageous when dispensing different resist compositions across different portions of the substrate.

[0804] Figures 15A and 15B illustrate the various steps in manufacturing a waveguide with a stepped pattern by depositing patternable material of different compositions in different regions of the waveguide. The first step includes, as shown in Figure 15A, providing a first patterned layer 1503 consisting of a patternable material of a first composition (e.g., a first resist material or a first polymer) on a first portion of the waveguide 1501, and providing a second patterned layer 1505 consisting of a patternable material of a second composition (e.g., a second resist material or a second polymer) on a second portion of the waveguide 1501. The first patterned layer 1503 can be provided by depositing the patternable material of a first composition on a first portion of the waveguide 1501 (e.g., using jet deposition techniques). The second patterned layer 1505 can be provided by depositing a patternable material of a second composition onto the second portion of the waveguide 1501 (for example, using jet deposition techniques). The thicknesses of the deposited layer of the patternable material of the first composition and the deposited layer of the patternable material of the second composition can be identical, as shown in Figure 15A. However, in some embodiments, the heights of the deposited layer of the patternable material of the first composition and the deposited layer of the patternable material of the second composition may differ. The deposited layers of the patternable material of the first and second compositions can be patterned using an imprint template. The imprint template can be configured to imprint the same pattern onto the deposited layer of the patternable material of the first composition and the deposited layer of the patternable material of the second composition, as shown in Figure 15A. However, in other embodiments, the imprint template can be configured to imprint different imprint patterns onto the deposited layer of the patternable material of the first composition and the deposited layer of the patternable material of the second composition. In various embodiments, the patternable material of the first composition and the patternable material of the second composition may include patternable materials having different etching rates.A layer deposited with the first composition may etch more slowly, resulting in diffraction features with greater heights within the waveguide 1501, while a layer deposited with the first composition may etch more quickly, resulting in diffraction features with shorter heights. In various embodiments, the patternable material of the first composition and the patternable material of the second composition may have different percentage silicon (Si) weight ratios, such that the etching rates of the first and second resist materials differ in their -F, Ar, -CH, and O-based chemical properties. For example, the patternable material of the first composition and the patternable material of the second composition may be selected from a general class of imprint resists made of silicon, as described in U.S. Patent No. 7,282,550, which can be used to enhance etching selectivity. U.S. Patent No. 7,282,550 is incorporated herein by reference in its entirety. The compositions of the patternable material of the first composition and the patternable material of the second composition can be analogous to compositions 1, 2, 3, 4, 5, 6, 7, and 8 described in U.S. Patent No. 7,282,550 (which is incorporated herein by reference as a whole). Thus, in some implementations, waveguides with stepped patterns can be fabricated using a one-step etching recipe, as shown in Figure 15B. However, other methods may also be employed. E. Waveguides with multilayer coatings

[0805] Various embodiments of waveguides described herein can be provided with multilayer coatings patterned to have features with different heights, depths, and / or pitches by using different etching, possibly stepwise etching methods, as described above. In some implementations, the multilayer coating may include at least two layers made of materials with different refractive indices. Embodiments of such waveguides are shown in Figures 16A-2, 16B-2a, 16B-2b, and 16C-2. Advantageously, the multilayer coatings can reduce losses due to reflection and / or reduce visual artifacts. In some implementations, features with different heights and / or pitches may be useful in providing amplitude and / or phase modulation of light propagating through the waveguide by total internal reflection. Methods for fabricating such embodiments of waveguides are described below.

[0806] A first embodiment of a waveguide 1601 having multiple features 1610 is shown in Figure 16A-2. The multiple features 1610 comprises multiple layers of material having different refractive indices. The embodiment shown in Figure 16A-2 can be manufactured by providing a waveguide 1601 coated with a multilayer coating as shown in Figure 16A-1, and by forming a patterned layer 1603 across the multilayer coating. The multilayer coating may comprise multiple layers 1605, 1607, and 1609 having different refractive indices. For example, as shown in Figure 16A-1, the multilayer coating may comprise a first layer 1605 closest to the waveguide, made of TiO2 having a refractive index of approximately 2.2 to 2.3; a second layer 1607, a central layer, made of Si3N4 having a lower refractive index than the first layer, for example, approximately 1.9; and a third layer 1609 furthest from the waveguide, made of SiO2 having a lower refractive index than the second layer, for example, approximately 1.45. Therefore, the refractive index can be stepped from high to low refractive index values ​​from the layer closest to the waveguide to the layer furthest from the waveguide. Therefore, in some implementations, such multilayer coatings can gradually match the refractive index of the waveguide 1601 to that of the ambient environment (e.g., air), which can be about 2.3-2.4 for LiNbO3, thereby reducing optical losses related to light incident on the waveguide 1601 from the ambient environment due to Fresnel reflection, etc., and / or light propagating within the waveguide by total internal reflection. In such embodiments, the amplitude of light propagating through total internal reflection (TIR) ​​can be modulated by the multilayer coating. In addition, the amount of world light passing through the waveguide can be increased in such embodiments. Furthermore, the amount of afterimage reflection of virtual light can also be reduced in such embodiments.

[0807] The patterned layer 1603 can be obtained by depositing a layer of patternable material (e.g., polymer or resist) over a multilayer coating using various deposition techniques, including, but not limited to, jet deposition techniques, and then patterning the deposited layer of patternable material (e.g., resist) using an imprint template or other lithography method. In some implementations, the height of the deposited layer of patternable material may vary across the surface of the multilayer coating. The deposited layer of patternable material can be patterned using an imprint template, which has features with different heights, depths, pitches, and / or arrangements, as shown in Figure 16A-1, to obtain a patterned layer 1603 with features with different heights, depths, and / or pitches. The patterned layer 1603 can be etched using the single-step or multi-step etching techniques discussed above, for example, using the chemical properties of F, Ar, O, and CH. The results are shown in Figure 16A-2. As shown in the figure, the upper parts of the diffraction features formed within the waveguide are at the same height, but the depth between the diffraction features varies. In this design, for example, the depth gradually increases. This effect occurs because the etching rate of the material in the multilayer upper layer 1609 (e.g., SiO2 in this embodiment) is sufficiently slower than the e...

Claims

1. An optical device, A substrate made of a first material having a first refractive index greater than 2.0, wherein the substrate includes a waveguide that is transparent to visible light, A plurality of diffraction features formed on the substrate, wherein each of the plurality of diffraction features is a plurality of diffraction features that are separated laterally from each other on the substrate, A second material arranged across the plurality of diffraction features, wherein the second material has a second refractive index lower than the first refractive index. Equipped with, An optical device in which the thickness of the second material, arranged on the plurality of diffraction features, gradually increases along the lateral direction of the substrate.

2. The optical device according to claim 1, wherein the first material comprises at least one of lithium niobate or silicon carbide.

3. The optical device according to claim 1, wherein the first refractive index is at least 2.

3.

4. The optical device according to claim 1, wherein the second material is a photoresist.

5. The optical device according to claim 4, wherein the plurality of diffraction features are contained within an internally coupled optical element, and the internally coupled optical element is arranged to receive light and couple the light into the waveguide so as to be guided therein.

6. The optical device according to claim 5, wherein the plurality of diffraction features are contained within an external coupling optical element, the external coupling optical element is arranged to couple at least a portion of the light induced in the waveguide to the outside of the waveguide, and the external coupling optical element is spaced apart from the internal coupling optical element.

7. The optical device according to claim 1, wherein the second refractive index is less than 1.

8.

8. The optical device according to claim 1, wherein the plurality of diffraction features are arranged in a one-dimensional array.

9. The optical device according to claim 1, wherein the plurality of diffraction features are arranged in a two-dimensional array.

10. The optical device according to claim 1, wherein the plurality of diffraction features are contained within an internally coupled optical element, and the internally coupled optical element is arranged to receive light and couple the light into the waveguide so as to be guided therein.

11. The optical device according to claim 1, wherein the plurality of diffraction features are contained within an external coupling optical element, and the external coupling optical element is arranged to couple at least a portion of the light being induced in the waveguide to the outside of the waveguide.

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