Low light leakage and high efficiency waveguide design

Abstract

Embodiments of the present disclosure generally relate to optical devices. More specifically, the embodiments described herein relate to waveguides with gratings to reduce light leakage and improve efficiency. In one embodiment, a waveguide includes an input coupler grating and an output coupler grating disposed on a waveguide substrate. The input coupler grating includes a plurality of blazed structures for input coupling light into the waveguide, and a metal coating disposed on the plurality of blazed structures. The output coupler grating includes a plurality of tilted structures, where each of the plurality of tilted structures includes a tilted surface angled at a tilt angle with respect to a surface normal to the waveguide substrate.

Description

Background Technology Technical Field

[0002] The embodiments of this disclosure generally relate to optical devices. More specifically, the embodiments described herein relate to waveguide combiners with gratings that reduce light leakage and improve efficiency. Related technical descriptions

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

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

[0005] One such challenge includes light leakage from AR devices. Light leakage typically represents light visible on the outer side of the AR device. Light leakage causes distracting light to be projected from the waveguides of the augmented reality device onto the outer side. Therefore, there is a need in the art to reduce the amount of light leakage projected onto the outer side of the augmented reality device. Summary of the Invention

[0006] In one embodiment, a waveguide is provided. The waveguide includes a waveguide substrate and an input coupler grating disposed on the waveguide substrate. The input coupler grating includes a plurality of blazed structures for coupling light input into the waveguide, and a metallic coating disposed on the plurality of blazed structures. The waveguide also includes an output coupler grating disposed on the waveguide substrate. The output coupler grating includes a plurality of tilted structures operable to couple light output from the waveguide. Each of the plurality of tilted structures includes a tilted surface angled relative to a surface perpendicular to the waveguide substrate at a tilt angle greater than about 40 degrees.

[0007] In another embodiment, a waveguide is provided. The waveguide includes a waveguide substrate and an input coupler grating disposed on a first surface of the waveguide substrate. The input coupler grating includes a plurality of tilted structures for coupling light input into the waveguide. The waveguide also includes an output coupler grating disposed on a second surface of the waveguide substrate, opposite the input coupler grating. The output coupler grating includes a second plurality of tilted structures operable to couple light output from the waveguide. Each of the second plurality of tilted structures includes a tilted surface angled relative to a surface perpendicular to the waveguide substrate at a tilt angle greater than about 40 degrees. A filler material is disposed between each of the second plurality of tilted structures.

[0008] In another embodiment, a waveguide is provided. The waveguide includes a waveguide substrate and an input coupler grating disposed on the waveguide substrate. The input coupler grating includes a plurality of tilted structures for coupling light input into the waveguide. The waveguide also includes an intermediate grating disposed on the waveguide substrate and adjacent to the input coupler grating, and an output coupler grating disposed on the waveguide substrate. The intermediate grating includes a plurality of binary structures having sidewalls perpendicular to the waveguide substrate, and the output coupler grating includes a plurality of blazed structures operable to couple light output from the waveguide. A packaging coating is disposed on the top surfaces of the plurality of blazed structures of the output coupler grating. Attached Figure Description

[0009] To gain a more detailed understanding of the features described above in this disclosure, a more specific description of the disclosure can be made with reference to embodiments (briefly outlined 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 construed as limiting their scope, allowing for other equally effective embodiments.

[0010] Figure 1 This is a perspective front view of a waveguide according to certain embodiments.

[0011] Figure 2A and Figure 2B This is a schematic cross-sectional view of a waveguide according to certain embodiments.

[0012] Figure 2C This is a schematic cross-sectional view of a blazing device structure according to certain embodiments.

[0013] Figure 2D This is a schematic cross-sectional view of a waveguide according to certain embodiments.

[0014] Figures 3A to 3C This is a schematic cross-sectional view of a waveguide according to certain embodiments.

[0015] Figures 4A to 4CThis is a schematic cross-sectional view of a portion of a waveguide according to certain embodiments.

[0016] Figure 5 This is a schematic cross-sectional view of a portion of a waveguide according to certain embodiments.

[0017] Figure 6 This is a schematic cross-sectional view of a portion of a waveguide according to certain embodiments.

[0018] Figure 7 This is a schematic cross-sectional view of a portion of a waveguide according to certain embodiments.

[0019] Figure 8A and Figure 8B This is a schematic cross-sectional view of a portion of a waveguide according to certain embodiments.

[0020] Figure 9A and Figure 9B This is a schematic cross-sectional view of a portion of a waveguide according to certain embodiments.

[0021] For ease of understanding, the same reference numerals are used where possible to denote common elements in the figures. It is contemplated that elements and features of one embodiment may be advantageously incorporated into other embodiments without further elaboration. Detailed Implementation

[0022] Embodiments of this disclosure generally relate to optical devices. More specifically, the embodiments described herein relate to waveguide combiners, such as augmented reality waveguide combiners with gratings for reducing light leakage. Certain details are set forth in the following description and figures to provide a thorough understanding of the various embodiments of this disclosure. Other details of well-known structures and systems often associated with waveguide displays and gratings are not set forth in the following disclosure to avoid unnecessarily obscuring the description of the various embodiments.

[0023] Many details, dimensions, angles, and other features shown in the figures are merely illustrative of specific embodiments. Therefore, other embodiments may have different details, components, dimensions, angles, and features without departing from the spirit or scope of this disclosure. Furthermore, other embodiments of this disclosure may be practiced without some of the details described below.

[0024] Augmented reality (AR) devices include a user's field of view (FOV). The user's FOV is the point at which the user perceives the virtual image on the AR display. The user's FOV is determined by the angle of light reflected from the output coupler grating of the waveguide to the user's eye. Light projects content (e.g., images or text) toward the user. Light coupled from the waveguide output can also diffract outwards. Light exits the waveguide at the same angle as the angle at which it is projected into the waveguide by the input coupler grating. Light diffracted away from the user or exiting the waveguide through the outer side of the AR device is commonly referred to as "light leakage" because the diffracted light to the outside world is visible to an observer near the user. For near-eye display waveguides, high levels of light leakage are undesirable because they reduce visibility to the user's eye, distract attention from other things, and are generally a sign of low waveguide efficiency. Light leakage leads to inefficiency because light leakage reduces the amount of light coupled from the output to the user's eye. Therefore, reducing light leakage will correspondingly improve the efficiency of the waveguide. As described herein, light is coupled from the waveguide output at the same angle as the angle at which it is coupled into the waveguide by the input. Configuring the waveguide's output coupler to include gratings (which are tuned to reflect light toward the user at a corresponding optical input coupling angle) reduces the amount of light leaving the waveguide on the outer side. Accordingly, in some embodiments of this disclosure that can be combined with other embodiments, a waveguide architecture configured to couple more light toward the user output is provided to reduce light leakage or undesired diffraction of light projected from the outer side of the waveguide.

[0025] When evaluating light leakage, the ratio between the efficiency of light diffracting towards the user and the efficiency of light diffracting towards the outside is considered based on the following equation:

[0026]

[0027] By increasing the efficiency of light diffracting towards the user and decreasing the efficiency of light diffracting towards the outside, the user / outside ratio increases. Since light leakage is the reciprocal of the user / outside ratio, increasing the user / outside ratio translates to a decrease in light leakage. Therefore, and as mentioned above, the reduction in light leakage caused by the waveguide can also indicate a corresponding increase in waveguide efficiency due to a decrease in the coupling of leaked or leaked light output to the outer side of the waveguide.

[0028] In some embodiments, a waveguide with a tilted structure of a grating serving as an output coupler grating is provided. Without being limited by theory, it is believed that using a tilted structure in the grating of the output coupler grating of the waveguide allows for tuning and control of the portion and intensity of light diffracted from the waveguide toward the user and away from the user (i.e., toward the outside) by the output coupler grating, in order to control and minimize light leakage. Specifically, the tilt angle and tuned dimensions of the tilted structure, such as the grating height, stub layer height, grating top width, and grating bottom width, can be modified in any suitable manner to increase the portion of light diffracted toward the user and decrease the portion of light diffracted toward the outside. For example, it has been observed that, compared to an output coupler grating formed using a binary structure in which the user / outside ratio is between about 1.5:1 and about 2:1, the tilted structure can provide a user / outside ratio between about 40:1 and about 60:1, depending on various other tuned dimensions of the grating. For example, in other embodiments, the waveguide including the output coupler grating structure can be further modified to include a blazed structure, a tilted structure with different shapes, one or more wrapping coatings, one or more underlayers and / or one or more grating materials, in order to control and improve the corresponding efficiency of the waveguide, thereby minimizing light leakage.

[0029] Figure 1 This is a perspective front view of waveguide 100. It should be understood that waveguide 100 described herein is an exemplary optical device. In some embodiments that may be combined with other embodiments described herein, waveguide 100 is a waveguide combiner, such as an augmented reality waveguide combiner. Waveguide 100 may be a waveguide used in near-eye display systems. In another embodiment that may be combined with other embodiments described herein, waveguide 100 is a planar optical device, such as a metasurface.

[0030] Waveguide 100 includes a plurality of structures 102. These structures 102 may be disposed above, below, or on the top surface 101A of substrate 101, or disposed within substrate 101. In another embodiment, the plurality of structures 102 may be formed above, below, on, or therein of a grating material layer (not shown) disposed on substrate 101. These structures 102 may include nanostructures having sub-micron dimensions (e.g., nanometer-sized dimensions). In some embodiments that may be combined with other embodiments described herein, regions of these structures 102 correspond to one or more gratings 104. In some embodiments that may be combined with other embodiments described herein, waveguide 100 includes at least one input coupler grating 104A (e.g., an input coupling grating) and an output coupler grating 104C (e.g., an output coupler grating). In some embodiments that may be combined with other embodiments described herein, waveguide 100 further includes an intermediate grating 104B (e.g., a pupil dilator grating).

[0031] The input coupler grating of waveguide 100 receives an incident beam (virtual image) of a certain intensity from a microdisplay. The input coupler grating divides the incident beam into multiple modes, each beam having one mode. The zero-order mode (T0) beam is refracted back into waveguide 100 or lost therein, the positive first-order mode (T1) beam passes through waveguide 100 and couples to the intermediate grating, and the negative first-order mode (T... -1 The incident beam propagates in the waveguide 100 in the opposite direction to the T1 beam. Ideally, the incident beam is split into a T1 beam with the full intensity of the incident beam to guide the virtual image to the intermediate region. The T1 beam coupled to the intermediate region is then split into a T0 beam refracted back into or lost in the waveguide 100, a T1 beam undergoing TIR until the T1 beam contacts another grating of the intermediate grating 104B, and a T0 beam coupled through the waveguide 100 to the output coupler grating. -1 beam.

[0032] T is coupled to the output coupler grating via waveguide 100. -1 The beam undergoes TIR in waveguide 100 until T -1 Up to the output coupler grating 104C, where T... -1 The beam is split into a T0 beam that is refracted back into waveguide 100 or lost therein, a T1 beam that undergoes TIR until it contacts another grating of the output coupler grating 104C, and a T0 beam that couples out of waveguide 100. -1 The beam. The T1 beam, having undergone TIR within the output coupler grating, continues to propagate until it passes through waveguide 100 and couples to the T1 beam of the output coupler grating. -1 The beam intensity is exhausted, or the remaining T1 beam propagating through the output coupler grating reaches the end of the output coupler grating. The output coupler grating 104C, corresponding to the output coupler grating of waveguide 100, can be tuned to control the T1 beam coupled to the output coupler grating through waveguide 100. -1 The beam is used to control the T coupled out of waveguide 100. -1 The intensity of the light beam. In some embodiments, the output coupler grating 104C may be formed with a tilted grating structure to tune and control each of the portion or intensity of light diffracted from the output coupler grating toward the user and diffracted away from the user (i.e., toward the outside). In these embodiments, the T transmitted through the waveguide 100 to the output coupler grating is controlled. -1 One approach to beam adjustment is to optimize the tilt angle of the tilt structure of the output coupler grating 104C to adjust the field of view and increase the viewing angle. Furthermore, adjusting the tilt angle and / or other dimensions of the tilt structure can provide an adjustment of the ratio between the portion of light diffracted towards the user and the portion diffracted towards the outside.

[0033] Figure 2A and Figure 2B This is a schematic cross-sectional view of waveguide 100 according to certain embodiments. Figure 2A As shown, waveguide 100 includes a substrate 101, a grating material layer 202 disposed on a top surface 101A of the substrate 101, and an anti-reflective (AR) coating 203 disposed on a bottom surface 101B of the substrate 101 opposite to the top surface 101A. In some embodiments, waveguide 100 also includes a plurality of blazed structures 204 corresponding to the input coupler grating 104A of waveguide 100 (i.e., the input coupling grating of waveguide 100), a plurality of binary structures 206 corresponding to the intermediate grating 104B of waveguide 100 (i.e., the pupil dilation grating of waveguide 100), and a plurality of tilted structures 208 corresponding to the output coupler grating 104C (i.e., the output coupler grating of waveguide 100).

[0034] In some embodiments, the blazed structure 204 of the input coupler grating 104A may be disposed within the grating material layer 202 (e.g., Figure 2A (as shown) or on it (such as) Figure 2B (As shown). In one embodiment, waveguide 100 may be an augmented reality waveguide combiner for a near-eye display system. Therefore, these plurality of blazed structures 204 (see below) Figure 2D (As described) can adjust the light projected toward waveguide 100 and couple the light input into waveguide 100.

[0035] Figure 2C A schematic cross-sectional view of the shimmering structure 204 according to one or more embodiments of this disclosure is shown. See also Figure 2C The blazing structure 204 includes a first blazing surface 205, a second blazing surface 207 opposite to the first blazing surface 205, a top surface 209, a bottom surface 211 opposite to the top surface 209, a grating depth "h", and a top width "T". w Bottom width "B" w The linewidth "d" is also specified. The grating depth "h" can range from about 10 nanometers to about 500 nanometers; for example, from about 50 nanometers to about 80 nanometers; or from about 20 nanometers to about 40 nanometers. The first blazing surface 205 forms a blazing angle "A". The blazing angle "A" can be from about 50 degrees to about 80 degrees relative to the plane 213 perpendicular to the substrate 101, for example, from about 60 degrees to about 70 degrees with respect to the plane 213. The second blazing surface 207 forms a blazing angle "B". The blazing angle "B" can be from about 0 degrees to about 40 degrees with respect to the plane 213, for example, from about 10 degrees to about 30 degrees with respect to the plane 213. The top duty cycle is defined as (top width T) w / raster period). The top duty cycle can range from approximately 0% to approximately 40%, for example, from approximately 10% to approximately 20%. The bottom duty cycle is defined as (bottom width B).w / grating period). The bottom duty cycle can range from approximately 55% to approximately 100%, for example, from approximately 60% to approximately 80%.

[0036] In some embodiments that can be combined with other embodiments described herein, the blaze angles "A" and / or "B" of two or more blaze structures 106 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 structures 106 are the same. In some embodiments that can be combined with other embodiments described herein, the depth h of two or more blaze structures 204 is different. In another embodiment that can be combined with other embodiments described herein, the depth h of two or more blaze structures 204 is the same.

[0037] In one embodiment, the input coupler grating 104A may also include a metal coating 210 disposed on the plurality of blazed structures 204 to improve the input coupling efficiency of the input coupler grating 104A. In some embodiments that may be combined with other embodiments described herein, the metal coating 210 comprises, is composed of, or is substantially composed of one or more metals. The metal coating 210 may include, but is not limited to, transparent conductive materials (e.g., indium-tin-oxide (ITO), fluorine-doped tin oxide (FTO), or doped zinc oxide), silver, aluminum, gold, or combinations thereof. In one example, the metal coating 210 is aluminum. The metal coating 210 may be of any suitable shape. In some embodiments that may be combined with other embodiments, the metal coating 210 is disposed on the blazed structure 204 (e.g., Figure 2A (as shown) or on it (such as) Figure 2B (As shown) a positive-form coating is formed. In other embodiments that may be combined with other embodiments, the metal coating 210 forms a blanket coating or overfills the pattern defined by the blazing structure 204. In some embodiments that may be combined with other embodiments described herein, the metal coating 120 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.

[0038] The plurality of binary structures 206 of the intermediate grating 104B can be in the grating material layer 202 (e.g. Figure 2A(As shown). Each of the plurality of binary structures 206 is separated by gaps (e.g., grooves). Each binary structure 206 includes a pair of sidewalls that are generally parallel to each other and generally perpendicular to the bottom surface of the gap between each of the plurality of binary structures 206. In some embodiments that may be combined with other embodiments described herein, the two or more binary structures 206 have different depths. In another embodiment that may be combined with other embodiments described herein, the two or more binary structures 206 have the same depth.

[0039] The plurality of tilted structures 208 of the output coupler grating 104C can also be in the grating material layer 202 (e.g. Figure 2A (As shown). The tilted structure 208 includes angled structures such that the corresponding bottom surface of the gap between each sidewall of the structure 208 and the gap between each of the tilted structures 208 forms a non-perpendicular angle. Each of the plurality of tilted structures 208 includes a height h and a lateral distance d. The height h of the plurality of structures 208 is defined as the distance from the top surface 214A of the bottom layer 214 to the top surface 208A of the structure 208. The gap g is the distance between adjacent tilted structures 208 of the output coupler grating 104C. In some embodiments, the gap g between each of the plurality of tilted structures 208 is substantially the same. In another embodiment, the gap g of at least one set of structures 208 is different from the gap g of an additional set of adjacent tilted structures 208 of the plurality of tilted structures 208. In some embodiments, each of the plurality of tilted structures 208 of the output coupler grating 104C may have the same tilt angle θ' relative to a plane 408 perpendicular to the substrate 101 or the bottom layer 214 (if present). In some embodiments, some of the structures 208 are formed with a tilt angle θ' relative to the surface 208 that differs from the other tilted structures 208 among the plurality of tilted structures 208. In some embodiments, the material used to form the grating material layer 202 of the plurality of tilted structures may be selected based on the desired depth and tilt angle of the structures 208. In some embodiments, the structures 208 may have a tilt angle θ' greater than about 40 degrees relative to the plane 408; for example, the tilt angle θ' may be about 45 degrees, 50 degrees, or 55 degrees.

[0040] In the embodiment of waveguide 100, the structures of the input coupler grating 104A, the intermediate grating 104B, and the output coupler grating 104C are all formed in the grating material layer 202, such as... Figure 2A As shown, for waveguide 100, only a single grating material layer 202 is deposited on substrate 101, and the top surface of each of the structures 204, 206, 208 is substantially coplanar with the top surface 202A of the grating material layer 202.

[0041] Any suitable method for depositing the grating material layer 202 can 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.

[0042] In one embodiment that can be combined with other embodiments described herein, structures 204, 206, and 208 can be formed by performing one or more etching processes in the grating material layer 202. For example, the etching process for forming the blazed structure 204 and the binary structure 206 may include (but is not limited to) at least one of ion beam etching (IBE), electron beam etching, or reactive ion etching (RIE). The etching process for forming the tilted structure 208 of the output coupler grating 104C can be formed by performing an angled etching process in the grating material layer 202.

[0043] In another embodiment, the shimmering structure 204 can be formed by performing an imprinting process. For example, as... Figure 2B As shown, the blazed structure 204 can be formed by locally depositing an imprintable material onto a portion of the top surface 202A of the grating material layer 202 and imprinting the imprintable material to form the blazed structure 204. In some embodiments, the nanoimprint resist may include at least one of spin-on glass (SOG), flowable SOG, organic, inorganic, and mixed (organic and inorganic) nanoimprintable materials, such materials may contain at least one of oxygen-containing silicon carbide (SiOC), titanium dioxide (TiO2), silicon dioxide (SiO2), vanadium oxide (IV) (VOx), aluminum oxide (Al2O3), indium tin oxide (ITO), zinc oxide (ZnO), tantalum pentoxide (Ta2O5), silicon nitride (Si3N4), titanium nitride (TiN), and zirconium dioxide (ZrO2).

[0044] In another embodiment, waveguide 100 also includes a gap-filling material 212 disposed between each of the tilted structures 208 of the output coupler grating 104C. The gap-filling material 212 can also be used to improve the output coupling efficiency of the output coupler grating 104C and is made of a material having a refractive index that is substantially matched or greater than that of the material of the tilted structure 208 (i.e., the grating material layer 202).

[0045] In some embodiments, the interstitial material 212 may include at least one of SOG, flowable SOG, organic nanoimprintable, inorganic nanoimprintable, and mixed (organic and inorganic) nanoimprintable materials, such as materials containing at least one of SiOC, TiO2, SiO2, VOx, Al2O3, ITO, ZnO, Ta2O5, Si3N4, TiN, and ZrO2. In some embodiments, the interstitial material 212 may be deposited between each of the inclined structures 208 using liquid casting, spin coating, liquid spraying, dry powder coating, screen printing, doctor blade coating, PVD, CVD, FCVD, or ALD processes.

[0046] The substrate 101 can be any substrate used in the art, and can be opaque or transparent to light of a selected wavelength, depending on the intended use of the substrate 101 as a waveguide substrate. The choice of substrate can include substrates of any suitable material, including but not limited to amorphous dielectrics, non-amorphous dielectrics, crystalline dielectrics, polymers, or combinations thereof. In some embodiments, the substrate 101 includes, but is not limited to, silicon-containing materials, silicon and oxygen-containing compounds, germanium-containing materials, indium and phosphide-containing compounds, gallium and arsenic-containing compounds, gallium and nitrogen-containing compounds, carbon-containing materials, silicon and carbon-containing compounds, silicon, carbon and oxygen-containing compounds, silicon and nitrogen-containing compounds, silicon, oxygen and nitrogen-containing compounds, niobium and oxygen-containing compounds, lithium, niobium and oxygen-containing compounds, aluminum and oxygen-containing compounds, indium, tin and oxygen-containing compounds, titanium and oxygen-containing compounds, lanthanum and oxygen-containing compounds, gadolinium and oxygen-containing compounds, zinc and oxygen-containing compounds, yttrium and oxygen-containing compounds, tungsten and oxygen-containing compounds, potassium and oxygen-containing compounds, phosphorus and oxygen-containing compounds, barium and oxygen-containing compounds, sodium and oxygen-containing compounds, or combinations thereof. In other embodiments that may be combined with other embodiments described herein, substrate 101 includes an oxide comprising one or more of a material containing gadolinium, silicon, sodium, barium, potassium, tungsten, phosphorus, zinc, calcium, titanium, tantalum, niobium, lanthanum, zirconium, lithium, or yttrium. Examples of substrate 101 materials include silicon (Si), silicon monoxide (SiO), silicon dioxide (SiO2), silicon carbide (SiC), fused silica, diamond, germanium quartz (Ge), silicon germanium (SiGe), indium phosphide (InP), gallium arsenide (GaAs), gallium nitride (GaN), sapphire, sapphire (Al2O3), lithium niobate (LiNbO3), indium tin oxide (ITO), lanthanum oxide (La2O3), gadolinium oxide (Gd2O5), zinc oxide (ZnO), yttrium oxide (Y2O3), tungsten oxide (WO3), titanium oxide (TiO2), zirconium oxide (ZrO3), sodium oxide (Na2O), niobium oxide (Nb2O5), barium oxide (BaO), potassium oxide (K2O), phosphorus pentoxide (P2O5), calcium oxide (CaO), or combinations thereof.

[0047] In this embodiment, the grating material layer 202 and the substrate 101 comprise different materials. The grating material layer 202 may include, but is not limited to, one or more of the oxides, carbides, or nitrides of silicon, aluminum, zirconium, tin, tantalum, zirconium, barium, titanium, hafnium, lithium, lanthanum, cadmium, niobium, or combinations thereof. Examples of materials for the grating material layer 202 include silicon carbide, silicon oxycarbide, titanium oxide, titanium dioxide, silicon oxide, silicon dioxide, vanadium oxide, aluminum oxide, aluminum-doped zinc oxide, indium tin oxide, tin oxide, zinc oxide, tantalum oxide, tantalum pentoxide, silicon nitride, titanium nitride, zirconium oxide, zirconium dioxide, niobium oxide, cadmium stannate, silicon oxynitride, barium titanate, diamond-like carbon, hafnium oxide, lithium niobate, silicon carbide, silver, cadmium selenide, mercury telluride, zinc selenide, silver indium gallium sulfide, silver indium sulfide, indium phosphide, gallium phosphide, lead sulfide, lead selenide, zinc sulfide, molybdenum sulfide, tungsten sulfide, or combinations thereof. In some embodiments that may be combined with other embodiments described herein, the material of the grating material layer 202 may have a refractive index between about 1.5 and about 2.65 (such as between about 2.0 and 2.6). In other embodiments that may be combined with other embodiments described herein, the material of the grating material layer 202 may have a refractive index of about 2.1, about 2.3, or about 2.5.

[0048] Figure 2C Another implementation of waveguide 100 is shown. For example... Figure 2C As shown, the input coupler grating 104A, the intermediate grating 104B, and the output coupler grating 104C can each be individually formed from the grating material layer 202 and partially disposed on a portion of the substrate 101. In one embodiment, the grating material layer 202 used to form each of the blazed structure 204, the binary structure 206, and the tilted structure 208 can be deposited to different thicknesses to provide variations in the size and tuned dimensions (e.g., height) of the structures 204, 206, and 208 subsequently formed therein. Therefore, unlike the top surface of the structures 204, 206, and 208 in waveguide 100 (which is coplanar with the top surface 202A of the grating material layer 202), the top surface of each of the structures 204, 206, and 208 in waveguide 220 can vary, such as... Figure 2C As shown.

[0049] In another embodiment, instead of forming the blazed structure 204 by etching the locally deposited grating material layer 202, the blazed structure 204 of the waveguide 220 can be formed by imprinting a locally deposited imprintable material (as discussed above) onto the waveguide 100. Similar to the waveguide 100, the waveguide 220 may also include a metal coating 210 disposed on the blazed structure 204 in the input coupler grating 104A, and a gap-filling material 212 between each of the tilted structures 208 disposed in the output coupler grating 104C, such as... Figure 2C As shown.

[0050] In one embodiment that may be combined with other embodiments herein, waveguide 220 may also include a bottom layer 214 disposed between structures 204, 206, 208 and substrate 101, such as Figure 2C As shown. The bottom layer 214 may be a material with a different refractive index than the grating material layer 202 used to form structures 204, 206, and 208. Similar to the waveguide 100 discussed above, the blazed structure 204 may be formed by imprinting or etching, the binary structure 206 may be formed by etching, and the tilted structure 208 may be formed by angled etching.

[0051] Figures 3A to 3C This is a cross-sectional view of waveguide 100 according to certain embodiments. In one embodiment, the input coupler grating 104A of waveguide 100 may alternatively be formed with a tilted structure 304. Waveguide 100 may also include a binary structure 206 corresponding to the intermediate grating 104B of waveguide 100 (i.e., the pupil dilation region of waveguide 100) and a tilted structure 208 corresponding to the output coupler grating 104C (i.e., the output coupler grating of waveguide 100). The tilted structure 304, the binary structure 206, and the tilted structure 208 may be mounted on the bottom layer 214 (e.g., ...). Figure 3A (as shown) or in the grating material layer 202 (as shown) Figure 3B (As shown). In one embodiment, the tilted structure 304 can be formed in a manner similar to the tilted structure 208 discussed above. For example, the tilted structure 304 can be formed using an angled etching process. In one embodiment, the tilted structure 304 may have a tilt angle θ' between about 10 degrees and about 60 degrees. In one embodiment, the tilted structure 304 may also include a gap-filling material (not shown) disposed between each of the tilted structures 304.

[0052] The inclined structure 304, binary structure 206, and inclined structure 208 formed on the bottom layer 214 can have different heights, such as Figure 3A As shown above. Figure 2C The waveguide 100, tilted structure 304, binary structure 206 and tilted structure 208 described herein may be individually formed by grating material layer 202 and locally disposed on a portion of substrate 101 or on bottom layer 214 (if present).

[0053] In another embodiment, the tilted structure 304 of the input coupler grating 104A can be formed on the bottom surface 101B of the substrate 101, opposite to the intermediate grating 104B and the output coupler grating 104C on the top surface 101A of the substrate 101. Figure 3CAs shown, the tilted structure 304 of the input coupler grating 104A can be formed by a grating material layer 202, which is partially deposited on a portion of the bottom surface 101B of the substrate 101, adjacent to the AR coating 203.

[0054] Figures 4A to 4C This is a cross-sectional view of the output coupler grating of a waveguide 100 according to certain embodiments. In one embodiment, the output coupler grating 104C for the waveguide 100 includes a plurality of tilted structures 208 formed on a base layer 214. In some embodiments, the waveguide 100 also includes a second base layer 404 disposed between the plurality of tilted structures 208 and the substrate 101. Figure 4B As shown, waveguide 100 may include a second layer 404 further formed between the underlying layer 214 and the substrate 101. Using more than one layer provides additional flexibility to tune the efficiency of waveguide 100. In one embodiment, the refractive index of the second layer 404 may be different from the refractive index of the underlying layer 214 and / or the refractive index of the material of the tilted structure 208. In one embodiment, the underlying layer 214 is made of a material having a refractive index of about 2.2, and the second layer 404 is made of a material having a refractive index of about 2.5.

[0055] like Figure 4C As shown, waveguide 100 may also include a second anti-reflective (AR) coating 406 disposed on the second surface 203B of AR coating 203, opposite to substrate 101. In one embodiment, the refractive index of the second AR coating 406 is between about 1.4 and about 2.0. In one embodiment, the refractive index of the second AR coating 406 is different from the refractive index of AR coating 203 and / or substrate 101.

[0056] In some embodiments, waveguide 100 includes a wrapping coating 402 disposed over the plurality of tilted structures 208 of output coupler grating 104C. The wrapping coating 402 comprises a flat surface formed on the structures 208 of output coupler grating 104C using a planar coating process (such as FCVD, PVD, or spin coating). In one embodiment, the wrapping coating 402 may comprise a material having a refractive index lower than or different from that of the grating material of the tilted structure 208 (i.e., grating material layer 202). In some embodiments, the refractive index of the wrapping coating 402 is between about 1.0 and about 1.7, such as between about 1.2 and about 1.5. In some embodiments, the wrapping coating 402 has an absorption coefficient less than about 0.001. The wrapping coating 402 may be formed of any suitable transparent material, including but not limited to silica-containing materials and silica-free materials, such as polymer-containing materials, for example, fluoropolymer materials. In some embodiments, the packaging coating 402 is formed of silicon dioxide (SiO2) or a low-dielectric-constant dielectric film (such as carbon-doped and nitrogen-doped silicon oxide (SiCON) or silicon carbonitride (SiCN)). In some embodiments, the packaging coating 402 includes a fluorinated material, such as aluminum fluoride (AlF3) and magnesium fluoride (MgF2). In other embodiments, the packaging coating 402 and the substrate 101 or the grating material layer 202 are formed of substantially the same material.

[0057] Figure 5 and Figure 6 This is a cross-sectional view of the output coupler grating of waveguide 100 according to certain embodiments. In one embodiment, the output coupler grating 104C of waveguide 100 may include a plurality of tilted structures 508 having tilted bottom surfaces 502 extending from the rear sidewall 506 toward the front sidewall 504 of adjacent structures 508. For example, as Figure 5 As shown, the bottom surface 502 of the gap (e.g., groove) between each of the inclined structures 508 may be angled away from the top surface 214A of the bottom layer 214 in order to form an inclined surface toward the front sidewall 504 of the adjacent structure 508.

[0058] In another implementation, such as Figure 6 As shown, the output coupler grating 104C of waveguide 100 can be formed to include a plurality of blazed structures 608. These plurality of blazed structures 608 can be similar to the blazed structure 204 discussed above. The blazed structures 608 can be formed in a grating material layer 202 disposed on substrate 101. The blazed structures 608 can be formed by locally deposited grating material layers 202 disposed on substrate 101 or on one or more underlying layers (i.e., underlying layer 214 and second underlying layer 404). The blazed structures 608 can be formed using an etching process or an imprinting process. Figure 5 and Figure 6The output coupler grating 104C formed in the illustrated embodiment may also include a packaging coating 402 disposed on the blazing structure 608.

[0059] Figure 7 This is a cross-sectional view of the output coupler grating of a waveguide 100 according to certain embodiments. In one embodiment, the waveguide 100 includes a plurality of tilted structures 704. The tilted structures 704 may be formed of a first grating material 706 and a second grating material 708 different from the first grating material 706. The first grating material 706 and the second grating material 708 may be any of the materials described above with respect to the grating material layer 202. The tilted structures 704 may be formed by depositing the second grating material 708 on the top surface 101A of the substrate 101 (or on one or more underlying layers, if present), depositing the first grating material 706 on the second grating material 708, and etching the first grating material 706 and the second grating material 708. The first grating material 706 may have a refractive index that is substantially matched or greater than that of the second grating material 708.

[0060] In one embodiment, the plurality of tilted structures 704 may also include a gap-filling material (not shown) similar to the gap-filling material 212 discussed above, which is disposed between each of the plurality of tilted structures 704. The waveguide 100 may also include a packaging coating 702 formed on the plurality of tilted structures 704. The packaging coating 702 may be formed as a conformal coating disposed on the tilted structures 704 of the output coupler grating 104C. Examples of suitable thin film deposition methods for forming the packaging coating 702 as a conformal coating include physical vapor deposition (PVD) (e.g., ion beam sputtering, magnetron sputtering, electron beam evaporation), chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD), atomic layer deposition (ALD), and inkjet printing.

[0061] Figure 8A and Figure 8B This is a cross-sectional view of the output coupler grating of a waveguide 100 according to certain embodiments. In one embodiment, the output coupler grating 104C may include the plurality of tilted structures 208 described above and a packaging coating comprising one or more materials disposed thereon. For example, the output coupler grating 104C may include the packaging coating 402 discussed above and a second coating 802 disposed on the structure 208 of the output coupler grating 104C. In some embodiments, a portion of the plurality of tilted structures 208 may contact each of the packaging coating 402 and the second coating 802, such as... Figure 8AAs shown. In other embodiments, these plurality of tilted structures 208 may be completely covered by the packaging coating 402, wherein a second coating 802 is subsequently disposed on the top surface 402A of the packaging coating 402, as shown. Figure 8B As shown. In this embodiment, the packaging coating 402 overfills the pattern defined by the plurality of inclined structures 208 and forms a planarized surface on the structures 208.

[0062] Figure 9A and Figure 9B This is a cross-sectional view of the output coupler grating of waveguide 100 according to certain embodiments. In one embodiment, the output coupler grating 104C of waveguide 100 may include the plurality of tilted structures 208 discussed above. The tilted structures 208 may be formed on a bottom layer 902 having a non-flat profile disposed on substrate 101. For example, as Figure 9A As shown, the bottom layer 902 can be formed with a linear tapered profile, wherein the thickness of the bottom layer 902 increases from one portion of the bottom layer 902 to another. The tapered profile of the bottom layer 902 can be formed using an etching process, such as selective area processing (SAP) etching, to remove portions of the bottom layer 902. Multiple inclined structures 208 can then be formed on the bottom layer 902. In another embodiment, as... Figure 9B As shown, the bottom layer 904 can be formed with contours of different thicknesses on the substrate 101 having multiple peaks. The bottom layer 904 can be formed using a gray-tone lithography process. Then, multiple tilted structures 208 can be formed on the bottom layer 904.

[0063] In summary, the embodiments of this disclosure described herein relate to waveguide combiners with different input coupler grating and output coupler grating designs. The different designs offer the benefits of reduced light leakage and improved efficiency.

[0064] Although the foregoing describes an embodiment of this disclosure, other and additional embodiments of this disclosure may be designed without departing from its basic scope, the scope of which is defined by the following claims.

Claims

1. A waveguide comprising: Waveguide substrate; An input coupler grating, the input coupler grating being disposed on the waveguide substrate, the input coupler grating comprising a plurality of blazed structures for coupling optical input to the waveguide, and a metal coating disposed on the plurality of blazed structures; and An output coupler grating is disposed on the waveguide substrate. The output coupler grating includes a plurality of tilted structures operable to couple light out of the waveguide. Each of the plurality of tilted structures includes a tilted surface at an angle greater than about 40 degrees relative to a surface perpendicular to the waveguide substrate.

2. The waveguide of claim 1, wherein the waveguide further comprises a gap-filling material disposed between each of the plurality of tilted structures.

3. The waveguide of claim 1, further comprising an intermediate grating disposed on the waveguide substrate, the intermediate grating comprising a plurality of binary structures having sidewalls perpendicular to the waveguide substrate.

4. The waveguide of claim 1, wherein the input coupler grating and the output coupler grating are formed in a grating material layer disposed on the waveguide substrate, and the top surfaces of the plurality of blazed structures are substantially coplanar with the top surfaces of the plurality of tilted structures.

5. The waveguide of claim 1, wherein the plurality of tilted structures are formed in a grating material layer disposed on the waveguide substrate, and the plurality of blazed structures comprise an imprintable material disposed on the grating material layer.

6. The waveguide of claim 1, further comprising an anti-reflective coating disposed on the surface of the waveguide substrate, opposite to the input coupler grating and the output coupler grating.

7. The waveguide of claim 1, further comprising a substrate disposed between the plurality of tilted structures and the waveguide substrate, wherein the plurality of tilted structures comprise a grating material having a refractive index different from that of the substrate.

8. The waveguide of claim 1, further comprising a packaging coating disposed on the top surface of the plurality of tilted structures, wherein the plurality of tilted structures comprise a grating material having a refractive index different from that of the packaging coating.

9. The waveguide of claim 8, wherein the packaging coating comprises a conformal coating disposed on the plurality of tilted structures of the output coupler grating.

10. The waveguide of claim 1, wherein the plurality of tilted structures comprises a first grating material disposed on the second grating material, and the first grating material is different from the second grating material.

11. A waveguide comprising: Waveguide substrate; An input coupler grating is disposed on a first surface of the waveguide substrate, and the input coupler grating includes a first plurality of tilted structures for coupling optical input to the waveguide; An output coupler grating is disposed on a second surface of the waveguide substrate, opposite to the input coupler grating. The output coupler grating includes a second plurality of tilted structures operable to couple light out of the waveguide. Each of the second plurality of tilted structures includes a tilted surface at an angle greater than about 40 degrees relative to a surface perpendicular to the waveguide substrate. as well as A gap-filling material is disposed between each of the second plurality of inclined structures.

12. The waveguide of claim 11, further comprising an intermediate grating disposed on the waveguide substrate, the intermediate grating comprising a plurality of binary structures having sidewalls perpendicular to the waveguide substrate.

13. The waveguide of claim 11, further comprising an anti-reflective coating disposed on the first surface of the waveguide substrate, adjacent to the input coupler grating.

14. The waveguide of claim 11, further comprising a substrate disposed between the second plurality of tilted structures and the waveguide substrate, wherein the second plurality of tilted structures comprises a grating material having a refractive index different from that of the substrate.

15. The waveguide of claim 11, further comprising a packaging coating disposed on the top surface of the second plurality of tilted structures, wherein the second plurality of tilted structures comprises a grating material having a refractive index different from that of the packaging coating.

16. A waveguide comprising: Waveguide substrate; An input coupler grating is disposed on the waveguide substrate, and the input coupler grating includes a plurality of tilted structures for coupling optical input to the waveguide; An intermediate grating is disposed on the waveguide substrate and adjacent to the input coupler grating. The intermediate grating includes a plurality of binary structures having sidewalls perpendicular to the waveguide substrate. An output coupler grating is disposed on the waveguide substrate and includes a plurality of blazed structures operable to couple light out of the waveguide. as well as A packaging coating is disposed on the top surface of the plurality of blazed structures of the output coupler grating.

17. The waveguide of claim 16, further comprising a gap-filling material disposed between each of the plurality of tilted structures of the input coupler grating.

18. The waveguide of claim 16, further comprising a substrate disposed between the plurality of blazed structures and the waveguide substrate, wherein the plurality of blazed structures comprise a grating material having a refractive index different from that of the substrate.

19. The waveguide of claim 16, further comprising an anti-reflective coating disposed on the surface of the waveguide substrate, opposite to the input coupler grating and the output coupler grating.

20. The waveguide of claim 16, further comprising a second packaging coating, the second packaging coating being different from the packaging coating disposed on the top surface of the packaging coating.

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