Functional embossed optical structures for optical devices

Abstract

Embodiments of the present disclosure provide methods for forming optical device structures. An exemplary method generally includes disposing a first material device layer on a substrate; patterning a portion of the first material device layer to form a first plurality of device structures in the first material device layer; disposing a second material device layer on an unpatterned portion of the first device material layer; performing a nanoimprint lithography process on the second material device layer to form a second plurality of device structures on the first material device layer; and disposing a metal coating on the second plurality of device structures.

Description

Technical Field

[0001] The embodiments of the present invention are generally related to optical devices for augmented, virtual, and mixed reality. More specifically, the embodiments described herein provide optical device structures for forming blared or stepped gratings. Background Technology

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

[0003] However, augmented reality enables experiences where users can still see through the display lenses of glasses or other HMD devices to observe their surroundings and see virtual object images generated for display and appearing as part of the environment. Augmented reality can include any type of input, such as audio and haptic input, as well as virtual images, graphics, and video, all of which enhance or augment the environment experienced by the user. As an emerging technology, augmented reality faces many challenges and design constraints.

[0004] One such challenge is displaying a virtual image superimposed on the surrounding environment. Optical devices, including waveguide combiners (such as augmented reality waveguide combiners) and planar optics (such as metasurfaces), are used to assist in image superposition. The generated light propagates through the optical devices until it exits and is superimposed on the surrounding environment. The optical devices may require a structure with a blaze angle relative to the surface of the optical device substrate. Conventionally, fabricating blaze optical device structures using one or more angled etching tools requires multiple lithography patterning steps and angled etching steps. Multiple lithography patterning steps and angled etching steps increase fabrication time and cost. Some of the challenges of waveguide displays with current grating designs and known materials also include low optical efficiency, stray light, ghosting, and a small field of view (FOV). Furthermore, fabricating current gratings on the same substrate can be a time-consuming process.

[0005] Therefore, there is a need in the art for improved methods of forming optical devices including blazing optical device structures. Summary of the Invention

[0006] Embodiments of this disclosure provide a method. The method typically includes disposing a first device material layer over a substrate, the first device material layer being a material different from the substrate; and patterning a portion of the first device material layer to form a first plurality of device structures in the top surface of the first device material layer. In some embodiments, the first plurality of device structures includes a first plurality of gratings and a second plurality of gratings. The method also includes disposing a second device material layer on the top surface of a portion of the first device material layer, and patterning the second device material layer using a nanoimprint lithography process to form a second plurality of device structures in the second material layer disposed on the first device material layer. In some embodiments, the second plurality of device structures includes a third plurality of gratings having a grating depth extending from the top surface of the first device material layer to the top surface of the third plurality of gratings. In some embodiments, the second device material layer comprises an uncured imprintable material for receiving a master mold of the nanoimprint lithography process. In some embodiments, the third plurality of gratings includes a plurality of blazed device structures or a plurality of stepped element structures.

[0007] In another embodiment of this disclosure, an optical device is provided. The optical device typically includes a substrate and a first device material layer disposed on the substrate, the first device material layer comprising a material different from that of the substrate. The optical device also includes a first plurality of device structures formed in a portion of the first device material layer and a second plurality of device structures disposed on an unpatterned portion of the first device material layer. In some embodiments, the first plurality of device structures includes a first plurality of gratings and a second plurality of gratings. In some embodiments, the first plurality of gratings corresponds to a pupil expansion grating of a waveguide combiner, and the second plurality of gratings corresponds to an output coupling grating of a waveguide combiner. In some embodiments, the second plurality of device structures includes a third plurality of gratings having a grating depth extending from the top surface of the first device material layer to the top surface of the third plurality of gratings. In some embodiments, the third plurality of gratings corresponds to an input coupling grating of a waveguide combiner and includes a plurality of blazed device structures or a plurality of stepped element structures. In other embodiments, the optical device may also include a metallic coating disposed on the second plurality of device structures. Attached Figure Description

[0008] To facilitate a detailed understanding of the above-described features of this disclosure, reference can be made to the embodiments for a more specific description of the disclosure briefly summarized above, some of which are illustrated in the accompanying drawings. However, it should be noted that the drawings illustrate only exemplary embodiments and should not be considered as limiting the scope of this disclosure, as other equivalent embodiments are permissible.

[0009] Figure 1A This is a front perspective view of an optical device according to an embodiment described herein.

[0010] Figure 1B This is an exemplary cross-sectional view of a plurality of device structures of an optical device according to embodiments described herein.

[0011] Figure 1C This is an exemplary cross-sectional view of the structure of the blazing device according to the embodiments described herein.

[0012] Figure 1D This is an exemplary cross-sectional view of a plurality of device structures of an optical device according to embodiments described herein.

[0013] Figure 1E This is an exemplary cross-sectional view of a stepped element structure according to the embodiments described herein.

[0014] Figure 2 This is a flowchart illustrating an exemplary method for manufacturing an optical device according to one or more embodiments described herein.

[0015] Figures 3A to 3H This is a schematic side sectional view of a substrate during the fabrication of a shimmering structure, according to one or more embodiments described herein.

[0016] Figure 4 This is a flowchart illustrating an exemplary method for manufacturing an optical device according to one or more embodiments described herein.

[0017] For ease of understanding, the same device symbols are used as much as possible to denote devices shared in the figures. It is contemplated that the devices and features of one embodiment may be advantageously incorporated into other embodiments without further reference. Detailed Implementation

[0018] The embodiments of the present invention generally relate to optical devices for augmented, virtual, and mixed reality. More specifically, the embodiments described herein provide manufacturing apparatus and methods for optical devices having an imprinted optical device structure disposed on top of a film layer, wherein additional optical device structures are integrated within the film layer.

[0019] In one embodiment, the optical device is a waveguide combiner having a high-refractive-index film disposed on a substrate and a plurality of device structures integrated in / formed in a portion of the top surface of the high-refractive-index film. The optical device also includes a plurality of device structures disposed on top of the high-refractive-index film on the substrate. In some embodiments, the plurality of device structures disposed on top of the high-refractive-index film include blazed device structures or stepped element structures, both configured to integrate optical device structures for optical coupling and guidance within the high-refractive-index film. Compared to conventional waveguides, the various embodiments discussed herein advantageously provide higher coupling efficiency, better image quality (e.g., lower ghosting, higher uniformity, etc.), and a simpler manufacturing process.

[0020] In one embodiment, the method utilizes imprinting combined with other formation techniques, such as lithography patterning and etching, to form an optical device. In some embodiments, the method uses conventional lithography patterning and etching processes to form multiple device structures in a high-refractive-index film, and uses imprinting to form multiple blazed device structures or multiple stepped element structures on the high-refractive-index film, eliminating the need for multiple lithography patterning steps and tilting etching steps. Using imprinting in combination with other techniques for forming optical devices using the methods and embodiments discussed herein provides a means to manufacture optical devices with high output while reducing costs.

[0021] Figure 1A The diagram illustrates a front perspective view of the optical device 100. It should be understood that the optical device 100 described below is an exemplary optical device. In one embodiment, which may be combined with other embodiments described herein, the optical device 100 is a waveguide combiner, such as an augmented reality waveguide combiner. In another embodiment, which may be combined with other embodiments described herein, the optical device 100 is a planar optical device, such as a metasurface. The optical device 100 includes a first plurality of device structures 102 and a second plurality of device structures 104 disposed on a substrate 101. In one embodiment, the first plurality of device structures 102 are integrated into and / or formed in a portion of a first device material layer 108 disposed on the substrate 101. In one embodiment, the second plurality of device structures 104 are formed in a second device material layer 110 spaced apart from the first plurality of device structures 102, the second device material layer 110 being disposed on the top surface of the remaining portion of the first device material layer 108. The first and second plurality of device structures 102, 104 may be nanostructures with submicron dimensions, such as nanometer-sized dimensions, such as critical dimensions less than 1 μm.

[0022] In one embodiment that can be combined with other embodiments described herein, a region of the first plurality of device structures 102 corresponds to one or more gratings 112, such as a first grating 112A and a second grating 112B. In another embodiment that can be combined with other embodiments described herein, a region of the second plurality of device structures 104 corresponds to a third grating 114. In one embodiment that can be combined with other embodiments described herein, the optical device 100 is a waveguide combiner that includes at least a first grating 112A corresponding to an intermediate or pupil expansion grating and a second grating 112B corresponding to an output coupling grating. According to the waveguide combiner of this embodiment that can be combined with other embodiments described herein, the waveguide combiner may include a third grating 114 corresponding to an input coupling grating.

[0023] The substrate 101 may be made of one or more of the following materials: silicon (Si), silicon dioxide (SiO2), germanium (Ge), silicon-germanium (SiGe), sapphire, silicon carbide (SiC), lithium niobium oxide (LiNbOx), and high-refractive-index transparent materials (such as high-refractive-index glass). For example, substrate 101 may comprise glass doped with heavily doped agents such as lanthanum (La), zirconium (Zr), zinc (Zn), and the like. Substrate 101 may comprise other suitable materials, including but not limited to amorphous dielectrics, non-amorphous dielectrics, crystalline dielectrics, silicon oxide, polymers, and combinations thereof. In some instances that may be combined with other embodiments described herein, substrate 101 comprises a transparent material. Suitable examples may include oxides, sulfides, phosphides, tellurides, or combinations thereof.

[0024] The material of substrate 101 may further have rollable and flexible properties. In one example, the material of substrate 101 includes, but is not limited to, materials with a refractive index between about 1.5 and about 2.4. For example, substrate 101 may be a doped high-refractive-index substrate with a refractive index between about 1.7 and about 2.4.

[0025] The first device material layer 108 may be disposed on the top surface of the optical device substrate, for example, through film deposition on the substrate 101 (if applicable). Any suitable method for depositing the first device material layer 108 may be used. Examples of suitable thin film deposition methods include physical vapor deposition (PVD) processes (e.g., ion beam sputtering, magnetron sputtering, electron beam evaporation), chemical vapor deposition (CVD) processes, plasma enhanced chemical vapor deposition (PECVD) processes, atomic layer deposition (ALD) processes, inkjet printing processes, or three-dimensional (3D) printing processes.

[0026] In some embodiments that can be combined with other embodiments described herein, the first device material layer 108 comprises a material different from that of the substrate 101. In some embodiments that can be combined with other embodiments described herein, the first device material layer 108 includes, but is not limited to, a material containing one or more of the following: silicon oxycarbide (SiOC), titanium dioxide (TiO2), silicon dioxide (SiO2), vanadium(IV) oxide (VOx), aluminum oxide (Al2O3), aluminum-doped zinc oxide (AZO), indium tin oxide (ITO), tin dioxide (SnO2), zinc oxide (ZnO), tantalum pentoxide (Ta2O5), silicon nitride (Si3N4), zirconium dioxide (ZrO2), niobium oxide (Nb2O5), cadmium stannate (Cd2SnO4), or silicon carbide (SiCN). In some embodiments that can be combined with other embodiments described herein, the material of the first device material layer 108 may have a refractive index between about 1.5 and about 2.65. In other embodiments that may be combined with other embodiments described herein, the first device material layer 108 may have a refractive index between about 3.5 and about 4.0.

[0027] In some embodiments that can be combined with other embodiments described herein, the second device material layer 110 includes an uncured patternable material layer for receiving an imprinted pattern from a nanoimprinting process to form a second plurality of device structures 104. In some embodiments, the second device material layer 110 is a patternable polymer or resistive material, including but not limited to UV-curable adhesives, thermoplastics, or other polymeric materials. The uncured patternable material can be deposited using deposition techniques such as, for example, jet deposition (e.g., inkjet deposition), coating, spin coating, spraying, or other predetermined amount of coating techniques such as stencils, doctor blades, blades, screens, etc.

[0028] Figure 1B An exemplary cross-sectional view of an optical device 100A according to certain embodiments is illustrated. In some embodiments that may be combined with other embodiments described herein, the first plurality of device structures 102 may include grating device structures having various shapes, such as, for example, linear (binary), columnar, diagonal or columnar, sawtooth, stepped, blazed, etc. In one embodiment that may be combined with other embodiments described herein, the first plurality of device structures 102 includes a binary device structure 116 of a waveguide combiner, such as a combined augmented reality waveguide.

[0029] In one embodiment that can be combined with other embodiments described herein, the second plurality of device structures 104 is a blazed device structure 118 of a waveguide combiner, such as Figure 1B As shown. In the illustrated example, the waveguide combiner includes a binary device structure 116 in the first and second gratings 112A, 112B and a blazed device structure 118 in the third grating 114. The third grating 114 corresponds to the input coupling grating of the optical device 100, which is configured to couple incident light into the optical device 100 and guide the light to the first grating 112A. The first grating 112A, corresponding to the intermediate or pupil expansion grating of the optical device 100, can propagate light through the optical device 100 via total internal reflection. The first grating 112A can then guide the light to the second grating 112B, corresponding to the output coupling grating of the optical device 100, which can extract the light and guide it out of the optical device 100 and into the observer's eye.

[0030] In some embodiments that can be combined with other embodiments described herein, the optical device 100 includes a metal coating 122 deposited on a second plurality of device structures 104. The metal coating 122 may have any suitable shape. In some embodiments that can be combined with other embodiments, the metal coating 122 forms a conformal coating on or over the blazing device structure 118 or the stepped element structure 120. In other embodiments that can be combined with other embodiments, the metal coating 122 forms a blanket coating or overfills a pattern defined by the blazing device structure 118 or the stepped element structure 120. In some embodiments that can be combined with other embodiments described herein, the metal coating 122 comprises, is composed of or is substantially composed of, one or more metals. The metal coating 122 includes, but is not limited to, transparent conductive materials (e.g., indium tin oxide (ITO), fluorine-doped tin oxide (FTO), or zinc oxide), silver, aluminum, gold, or combinations thereof. The thickness of the metal coating 122 is greater than the skin depth of the metal in the operating spectrum. In some embodiments that may be combined with other embodiments described herein, the metal coating 122 has a thickness from about 10 nanometers to about 100 nanometers; for example, from about 50 nanometers to about 80 nanometers; or from about 20 nanometers to about 40 nanometers.

[0031] Figure 1C The illustration shows an exemplary cross-sectional view of a blazing device structure 118 according to certain embodiments of this disclosure. Each blazing device structure 118 includes a first blazing surface 124, a second blazing surface 126 opposite to the first blazing surface 124, a top surface 128, a bottom surface 130 opposite to the top surface 128, a grating depth "h", and a top width "T". W Bottom width "B" W ", grating period and linewidth "d" (e.g. Figure 1B (As shown). The grating depth "h" can be from about 10 nanometers to about 500 nanometers; for example, from about 80 nanometers to about 150 nanometers; or from about 20 nanometers to about 70 nanometers. The first blazing surface 124 forms a blazing angle "A". The blazing angle A can be at an angle of about 50 degrees to about 80 degrees relative to the axis 125 perpendicular to the top surface 127 of the first device material layer 108, for example, at an angle of about 60 degrees to about 70 degrees relative to the vertical axis 125. The second blazing surface 126 forms a blazing angle "B". The blazing angle B can be at an angle of about 0 degrees to about 40 degrees relative to the axis 125, for example, at an angle of about 10 degrees to about 30 degrees relative to the vertical axis 125. The top duty cycle is defined as... The top duty cycle can be from about 0% to about 40% of the grating period, for example from about 15% to about 35%. In one embodiment, the grating period can be from about 250 nanometers to about 500 nanometers; for example from about 300 nanometers to about 400 nanometers. The bottom duty cycle is defined as... The bottom duty cycle can be from about 60% to about 100% of the grating cycle, for example from about 70% to about 90%.

[0032] In one embodiment that can be combined with other embodiments described herein, the blaze angles A and / or B of two or more blaze device structures 118 are different. In another embodiment that can be combined with other embodiments described herein, the blaze angles A and / or B of two or more blaze device structures 118 are the same. In one embodiment that can be combined with other embodiments described herein, the grating depth h of two or more blaze device structures 118 is different. In another embodiment that can be combined with other embodiments described herein, the grating depth h of two or more blaze device structures 118 is the same. In one embodiment that can be combined with other embodiments described herein, the linewidth d corresponds to the distance between the first blaze surfaces 124 of adjacent blaze device structures 118. In one embodiment that can be combined with other embodiments described herein, the linewidth d of two or more blaze device structures 118 is different. In another embodiment that can be combined with other embodiments described herein, the linewidth d of two or more blaze device structures 118 is the same.

[0033] Figure 1D An exemplary cross-sectional view of an optical device 100B according to certain embodiments is illustrated. In some embodiments, and in another embodiment that may be combined with other embodiments described herein, the second plurality of device structures 104 is a stepped element structure 120 of a waveguide combiner, such as... Figure 1D As shown. In the illustrated example, the waveguide combiner includes binary device structures 116 in the first and second gratings 112A and 112B, respectively corresponding to the pupil expansion and output coupling gratings of the optical device 100. In the illustrated example, the third grating 114, corresponding to the input coupling grating of the optical device 100, is a stepped element structure 120, configured to couple incident light into the optical device 100 and guide the light to the first grating 112A.

[0034] Figure 1E The illustration shows an exemplary cross-sectional view of a stepped element structure 120 according to certain embodiments of this disclosure. Each stepped element structure 120 includes a stepped surface 132 having a plurality of steps 134, sidewalls 136, a top surface 138, a bottom surface 140 opposite to the top surface 138, a grating depth "h", and a top width "T". W "、Step width "S W "Number of steps" N S Bottom width "B" W "、Step depth "S D The linewidth "d" is also specified. In some embodiments, the grating depth extending between the top surface and top surface 138 of the first device material layer 108 can be, for example, from about 80 nanometers to about 150 nanometers; or from about 20 nanometers to about 70 nanometers. In some embodiments, the grating depth h corresponds to the height of the sidewall 136. In some embodiments, the number of steps N of the stepped surface 132 is specified. S The steps include those ranging from 2 steps to approximately 100 steps; such as those ranging from approximately 3 steps to approximately 10 steps. In one embodiment, the stepped surface 132 includes 6 steps, as shown. In one embodiment, the stepped surface 132 forms a step angle “S”. The step angle S may be approximately 40 degrees to approximately 80 degrees relative to the axis 125 perpendicular to the top surface 127 of the first device material layer 108, for example, approximately 60 degrees to approximately 70 degrees relative to the vertical axis 125.

[0035] The top working cycle of each stepped element structure 120 is defined as The top duty cycle can be from about 0% to about 40%, for example from about 15% to about 35%. In one embodiment, the grating period can be from about 200 nanometers to about 400 nanometers; for example, from about 230 nanometers to about 280 nanometers; or from about 300 nanometers to about 370 nanometers. The bottom duty cycle is defined as... The bottom working cycle can be from about 60% to about 100%, for example from about 70% to about 90%.

[0036] In one embodiment that can be combined with other embodiments described herein, the step depth S D This corresponds to the distance between the top surfaces of adjacent steps 134 in the stepped element structure 120. In one embodiment, which can be combined with other embodiments described herein, the step depth S of two or more steps 134 is... D They are different. In another embodiment, which may be combined with other embodiments described herein, the step depth S of two or more steps 134 is different. D They are the same. In one embodiment, which can be combined with other embodiments described herein, the step width S W The width of the top surface of each step 134 corresponds to the distance between the top surface 138 and the bottom surface 140 of each stepped element structure 120. In one embodiment, which may be combined with other embodiments described herein, the step depth S of two or more steps 134 is... D They are different. In another embodiment, which may be combined with other embodiments described herein, the step depth S of two or more steps 134 is different. D They are the same.

[0037] In one embodiment that can be combined with other embodiments described herein, the linewidth d corresponds to the distance between the sidewalls 136 of adjacent stepped element structures 120. In one embodiment that can be combined with other embodiments described herein, the linewidth d of two or more stepped element structures 120 is different. In another embodiment that can be combined with other embodiments described herein, the linewidth d of two or more stepped element structures 120 is the same. In one embodiment that can be combined with other embodiments described herein, the step angle S of two or more stepped element structures 120 is different. In another embodiment that can be combined with other embodiments described herein, the step angle S of two or more stepped element structures 120 is the same. In one embodiment that can be combined with other embodiments described herein, the grating depth h of two or more stepped element structures 120 is different. In another embodiment that can be combined with other embodiments described herein, the grating depth h of two or more stepped element structures 120 is the same.

[0038] Figure 2 This is a flowchart of a method 200 for forming an optical device having a first plurality of device structures 102 and a second plurality of device structures 104, according to certain embodiments. Figures 3A to 3H This is an exemplary cross-sectional view of an exemplary optical device, such as waveguide 300 formed during the execution of method 200. Therefore, for clarity, Figure 2 and Figures 3A to 3H They are described together in this article.

[0039] although Figures 3A to 3H The illustration shows etching a first device material layer 108 to dispose of a first plurality of device structures 102 on a substrate 101; however, the substrate 101 may also be directly etched to dispose of the first plurality of device structures 102 within the substrate 101. In some embodiments, the waveguide 300 may correspond to... Figure 1A Optical device 100 in Figure 1B The optical device 100A and / or Figure 1D The optical device 100B is described herein. In one embodiment, which may be combined with other embodiments described herein, the substrate 101 may correspond to the substrate of a planar optical device to form a first plurality of device structures 102 and a second plurality of device structures 104 thereon. In another embodiment, which may be combined with other embodiments described herein, the substrate 101 may correspond to the substrate of a waveguide combiner to form a first plurality of device structures 102 and a second plurality of device structures 104 thereon.

[0040] Method 200 begins with operation 201, wherein a first device material layer 108 is disposed on a substrate 101. As described above, in one embodiment, the first device material layer 108 may be disposed on the top surface of the substrate 101 via a film deposition process. As described herein, the first device material layer 108 may be a high refractive index material layer.

[0041] In operation 202, a portion 302 of the first device material layer 108 is patterned (etched) to form a first plurality of device structures 102 in the top surface 304 of the first device material layer 108. In some embodiments, the portion 302 of the first device material layer 108 may be patterned by photolithography patterning and wet or dry etching processes. In one embodiment, as Figure 3B and Figure 3C As shown, the first plurality of device structures 102 patterned in the first device material layer 108 include a first grating 112A and a second grating 112B formed in the first device material layer 108. In some embodiments, as discussed herein, the first grating 112A and the second grating 112B may include grating device structures having various shapes, such as, for example, linear (binary), columnar, oblique or columnar, serrated, stepped, flared, etc. For example, the first grating 112A and the second grating 112B may include binary vertical device structures, such as... Figure 1B and Figure 1D The binary device structure 116 shown is illustrated.

[0042] In some embodiments, a first grating 112A and a second grating 112B may be disposed on waveguide 300, the gratings corresponding to the positioning of a pupil expansion grating and an output coupling grating, respectively. Thus, the first grating 112A may be configured to distribute and propagate light along waveguide 300 to the second grating 112B via total internal reflection. The second grating 112B may then be configured to couple the light propagating in waveguide 300 to the observer's eye. In some embodiments that may be combined with other embodiments herein, the first grating 112A and the second grating 112B are patterned simultaneously in operation 202 to form a first plurality of device structures 102 in a portion 302 of the first device material layer 108. In some embodiments that may be combined with other embodiments herein, the first grating 112A and the second grating 112B are patterned sequentially in operation 202 to form a first plurality of device structures 102 in a portion 302 of the first device material layer 108.

[0043] In operation 203, a second device material layer 110 is disposed above the top surface 304 of the unpatterned portion 308 of the first device material layer 108. As described above, the second device material layer 110 comprises an uncured imprintable material. In some embodiments, the second device material layer 110 may be an imprintable polymer or resist material that can be patterned by a nanoimprinting process, including but not limited to UV-curable adhesives, UV-curable resists, thermoplastics, or other polymeric materials. As described herein, the second device material layer 110 may be deposited on the first device material layer 108 using deposition techniques, such as jet deposition (e.g., inkjet deposition).

[0044] In operation 204, a nanoimprint lithography process is performed to form a second plurality of device structures 104 in the second device material layer 110. Operation 204 typically involves imprinting a master mold 306 into the second device material layer 110 to form a positive waveguide pattern. The master mold 306 has a negative waveguide pattern 310 with an inverted pattern 312. The inverted pattern 312 includes at least one of an inverted grating portion corresponding to the inversion of the third grating 114.

[0045] In some embodiments, the positive waveguide pattern includes at least one of a plurality of grating patterns, such as the waveguide grating pattern corresponding to the third grating 114, as... Figure 3E As shown. When repeating the manufacturing process to form waveguide 300, the same master mold 306 can be used in subsequent iterations of the method 200 described herein. Using the same master mold 306 to form the positive waveguide patterns of the second plurality of device structures 104 enables increased efficiency and higher output when manufacturing waveguide 300, because only a few lithography patterning steps and tilting etching steps need to be manually performed to form the master mold 306.

[0046] In another embodiment, operation 204 may typically include applying a patterned second device material layer 110 to an unpatterned portion of the first device material layer 108 by a master mold 306 through a printing process rather than an embossing process. The master mold 306 may be partially coated with a material of the second device material layer 110, wherein the master mold 306 has the property of forming a desired pattern of the second device material layer 110 on the first device material layer 108. As the master mold 306 contacts the first device material layer 108, the second device material layer 110 is transferred or printed onto the first device material layer 108.

[0047] After the second device material layer 110 is imprinted using the master mold 306, in operation 205, the positive waveguide pattern is cured to form the third grating 114 of the second plurality of device structures 104, as shown. Figure 3F As shown. The curing process performed typically depends on the material of the second device material layer 110. For example, in some embodiments, the second device material layer 110 includes a UV-curable inhibitor, so operation 205 includes exposing the imprinted second device material layer 110 to radiation, such as infrared (IR) radiation or ultraviolet (UV) radiation. In other embodiments, the second device material layer 110 includes a thermosetting material that can be cured by a solvent evaporation curing process. The solvent evaporation curing process may include thermal heating or infrared irradiation heating. After the positive waveguide pattern in the second device material layer 110 has cured, the master mold 306 is released.

[0048] Figure 3G The illustration shows a schematic cross-sectional view after the master impression 306 has been released in operation 205. In one embodiment, the master impression 306 may be coated with a single-layer non-stick surface treatment coating, such as a fluorinated coating, so that the master impression 306 can be mechanically removed by means of a mechanical tool or by manual peeling. In another embodiment, the master impression 306 may comprise a water-soluble polyvinyl alcohol (PVA) material so that the master impression 306 can be removed by dissolving it in water. In yet another embodiment, the master impression 306 includes a rigid backing plate, such as a glass sheet, to increase mechanical strength, thereby maintaining the integrity of the master impression 306 during and after release.

[0049] In method 200, the first and second plurality of device structures 102, 104 can be formed in any order. In some embodiments, after the first device material layer 108 is disposed over the substrate 101 in operation 201, operations 203 to 204 can be performed to form the second plurality of device structures 104 on a portion of the first device material layer 108. After the second device material layer 110 is patterned, operation 202 can then be performed to pattern the remaining portion of the first device material layer 108 not covered by the second device material layer 110 to form the first plurality of device structures 102 in the first device material layer 108.

[0050] In operation 206, a metallic coating 122 is formed over the third grating 114 of the second plurality of device structures 104, such as Figure 3H As shown. A metal coating 122 is applied to the exposed surface of the third grating 114. The metal coating 122 may have any suitable shape. In some embodiments that may be combined with other embodiments, the metal coating 122 forms a conformal coating over or on the third grating 114. In other embodiments that may be combined with other embodiments, the metal coating 122 forms a blanket coating or overfills the pattern defined by the third grating 114. Any suitable method for depositing the metal coating 122 may be used. Examples of suitable thin film deposition methods include physical vapor deposition (PVD) (e.g., ion beam sputtering, magnetron sputtering, or electron beam evaporation), chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD), atomic layer deposition (ALD), inkjet printing, or three-dimensional (3D) printing.

[0051] As described herein, the third grating 114 of the second plurality of device structures 104 may be configured to couple incident light input into the waveguide 300. In some embodiments, the metal coating 122 may therefore prevent / reduce reflection of the input coupled light from the opposing surface of the third grating 114. In other embodiments, an anti-reflective coating may be deposited over the second plurality of device structures 104 instead of over the metal coating 122. The refractive index of the material comprising the anti-reflective coating may be less than the refractive index of the material of the second plurality of device structures 104.

[0052] Figure 4This is a flowchart of a method 400 for forming an optical device having a first plurality of device structures 102 and a second plurality of device structures 104, according to certain embodiments. Method 400 begins at operation 401, wherein a first device material layer 108 is disposed over a substrate 101. As described herein, the first device material layer 108 may be a high refractive index material layer.

[0053] In operation 402, a portion 302 of the first device material layer 108 is patterned (etched) to form a first plurality of device structures 102 in the top surface 304 of the first device material layer 108. In some embodiments, the portion 302 of the first device material layer 108 may be patterned by photolithography and wet or dry etching processes. In one embodiment, as shown in Figures 3B and 3C, the first plurality of device structures 102 patterned in the first device material layer 108 includes a first grating 112A and a second grating 112B formed in the first device material layer 108. In some embodiments, as discussed herein, the first and second gratings 112A, 112B may include grating device structures having various shapes, such as, for example, linear (binary), columnar, diagonal or columnar, serrated, stepped, flared, etc.

[0054] In some embodiments, a first grating 112A and a second grating 112B may be disposed on waveguide 300, the gratings corresponding to the positioning of a pupil expansion grating and an output coupling grating, respectively. Thus, the first grating 112A may be configured to distribute and propagate light along waveguide 300 to the second grating 112B via total internal reflection. The second grating 112B may then be configured to couple the light propagating in waveguide 300 to the observer's eye. In some embodiments that may be combined with other embodiments herein, the first grating 112A and the second grating 112B are patterned simultaneously in operation 202 to form a first plurality of device structures 102 in a portion 302 of the first device material layer 108. In some embodiments that may be combined with other embodiments herein, the first grating 112A and the second grating 112B are sequentially patterned in operation 402 to form a first plurality of device structures 102 in a portion 302 of the first device material layer 108.

[0055] In operation 403, a second device material layer 110 is disposed above the top surface 304 of the unpatterned portion of the first device material layer 108. As described above, the second device material layer 110 comprises an uncured imprintable material. In some embodiments, the second device material layer 110 may be an imprintable polymer or resistive material that can be patterned by a nanoimprinting process, such polymers or resistive materials including, but not limited to, UV-curable adhesives, UV-curable resists, thermoplastics, or other polymeric materials. As described herein, the second device material layer 110 may be deposited on the first device material layer 108 using deposition techniques such as jet deposition (e.g., inkjet deposition).

[0056] In operation 404, the second device material layer 110 is patterned to form a second plurality of device structures 104. In some embodiments, the second plurality of device structures 104 may be configured to couple incident light input into the waveguide 300. In an embodiment, the second plurality of device structures 104 patterned in the second device material layer 110 includes a third grating 114. In some embodiments, as discussed herein, the third grating 114 may include having, for example, Figure 3G The blazing device structure shown or the grating device structure with a stepped element structure as shown in Figures 1D and 1E.

[0057] In some embodiments, patterning the second device material layer 110 in operation 404 may include a nanoimprint lithography process (as described in method 200 above). In other embodiments, operation 404 may include forming a third grating 114 of the second plurality of device structures 104 using one or more tilting etch tools and multiple lithography patterning and tilting etch steps.

[0058] In operation 405, a metallic coating 122 is formed over the third grating 114 of the second plurality of device structures 104, such as Figure 3HAs shown. A metal coating 122 is applied to the exposed surface of the third grating 114. The metal coating 122 may have any suitable shape. In some embodiments that may be combined with other embodiments, the metal coating 122 forms a conformal coating over or on the third grating 114. In other embodiments that may be combined with other embodiments, the metal coating 122 forms a blanket coating or overfills the pattern defined by the third grating 114. Any suitable method for depositing the metal coating 122 may be used. Examples of suitable thin film deposition methods include physical vapor deposition (PVD) (e.g., ion beam sputtering, magnetron sputtering, or electron beam evaporation), chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD), atomic layer deposition (ALD), inkjet printing, or three-dimensional (3D) printing.

[0059] As described herein, the third grating 114 of the second plurality of device structures 104 may be configured to couple incident light input into the waveguide 300. In some embodiments, the metal coating 122 may therefore prevent / reduce reflection of input coupled light from the opposing surface of the third grating 114. In other embodiments, an anti-reflective coating may be deposited over the second plurality of device structures 104 instead of on the metal coating 122. The refractive index of the material comprising the anti-reflective coating may be less than the refractive index of the material of the second plurality of device structures 104.

[0060] In summary, by forming a second device material layer 110 and then forming a second plurality of device structures 104 via nanoimprint lithography before or after forming a first plurality of device structures 104 in a first device material layer 108 disposed in a substrate 101, it is possible to manufacture the second plurality of device structures 104 having shimmering or stepped element structures with higher efficiency and lower cost. Therefore, the method for manufacturing shimmering or stepped element structures in the second device material layer 110 as described herein eliminates the need for using one or more tilting etching tools and multiple lithography patterning and tilting etching steps (these tools and steps are conventionally used to form shimmering and / or stepped element structures), resulting in increased efficiency, reduced manufacturing time, and lower costs.

[0061] Although the foregoing description is directed to embodiments of this disclosure, other and more embodiments of this disclosure may be designed without departing from the basic scope of this disclosure, the scope of which is defined by the appended claims.

Claims

1. A method for forming an optical device, comprising the following steps: A first device material layer is disposed on a substrate, the first device material layer being a material different from the substrate; A portion of the first device material layer is patterned to form a first plurality of device structures in the top surface of the first device material layer, the first plurality of device structures including a first plurality of gratings and a second plurality of gratings; A second device material layer is provided on the top surface of the unpatterned portion of the first device material layer, the second device material layer being an uncured imprintable material; and The second device material layer is patterned to form a second plurality of device structures, the second plurality of device structures including a third plurality of gratings. The third plurality of gratings includes a plurality of blazing device structures or a plurality of stepped element structures, and each of the third plurality of gratings includes a grating depth extending from the top surface of the first device material layer to the top surface of each of the corresponding third plurality of gratings.

2. The method of claim 1, wherein the first plurality of gratings corresponds to the pupil expansion grating of the waveguide combiner, and the second plurality of gratings corresponds to the output coupling grating of the waveguide combiner.

3. The method of claim 1, wherein the third plurality of gratings corresponds to the input coupling grating of the waveguide combiner.

4. The method of claim 1, further comprising the following steps: A metallic coating is applied to the third plurality of gratings.

5. The method of claim 1, wherein the step of patterning the second device material layer comprises the following steps: Patterning is performed using a nanoimprint lithography process, which includes the following steps: The master mold is imprinted onto the material layer of the second device, the mold including a plurality of inverted gratings that are opposite to the third plurality of gratings in the structure of the second plurality of devices; A curing process is performed on the material layer of the second device; Release the master mold from the material layer of the second device; and Annealing was performed on the material layer of the second device.

6. The method of claim 1, wherein the first device material layer comprises a high refractive index film material with a refractive index between about 1.4 and about 3.

5.

7. The method of claim 1, wherein the first device material layer comprises a material containing silicon oxycarbide (SiOC), titanium dioxide (TiO2), silicon dioxide (SiO2), vanadium oxide (IV) (VOx), aluminum oxide (Al2O3), aluminum-doped zinc oxide (AZO), indium tin oxide (ITO), tin dioxide (SnO2), zinc oxide (ZnO), tantalum pentoxide (Ta2O5), silicon nitride (Si3N4), zirconium dioxide (ZrO2), niobium oxide (Nb2O5), cadmium stannate (Cd2SnO4), or silicon carbide (SiCN).

8. The method of claim 1, wherein the second device material layer comprises a UV-curable adhesive, a UV-curable inhibitor, or other UV-curable polymer.

9. The method of claim 1, wherein the second device material layer comprises a thermosetting thermoplastic or other thermosetting polymer material.

10. The method of claim 1, wherein the step of patterning the portion of the first device material layer comprises the following steps: Perform photolithography patterning and etching processes.

11. An optical device, comprising: substrate; A first device material layer is disposed on the substrate, the first device material layer comprising a material different from the substrate; A first plurality of device structures are formed in a portion of the first device material layer, the first plurality of device structures including a first plurality of gratings and a second plurality of gratings; The second device material layer is disposed on a portion of the top surface of the first device material layer; and A second plurality of device structures are formed in the second device material layer, the second plurality of device structures including a third plurality of gratings. The third plurality of gratings includes a plurality of blazing device structures or a plurality of stepped element structures, and each of the third plurality of gratings includes a grating depth extending from the top surface of the first device material layer to the top surface of the corresponding third plurality of gratings.

12. The optical device of claim 11, wherein the first plurality of gratings corresponds to the pupil expansion grating of the waveguide combiner, and the second plurality of gratings corresponds to the output coupling grating of the waveguide combiner.

13. The optical device of claim 11, wherein the third plurality of gratings corresponds to the input coupling grating of the waveguide combiner.

14. The optical device of claim 11, further comprising a metal coating disposed on the third plurality of gratings.

15. The optical device of claim 11, wherein the third plurality of gratings is formed by a nanoimprint lithography process performed on the second device material layer disposed on the top surface of the first device material layer.

16. The optical device of claim 11, wherein the first plurality of gratings and the second plurality of gratings are formed by performing a photolithography patterning and etching process in the first device material layer.

17. The optical device of claim 11, wherein the first device material layer comprises a high refractive index film material with a refractive index between about 1.4 and about 3.

5.

18. The optical device of claim 14, wherein the metal coating comprises a reflective metallic material.

19. The optical device of claim 11, wherein the first plurality of gratings comprises a linear (binary), columnar, oblique or columnar, sawtooth, stepped, or flaring device structure.

20. The optical device of claim 11, wherein the second plurality of gratings comprises a linear (binary), columnar, oblique or columnar, sawtooth, stepped, or flaring device structure.

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