# US 2020/0400951 A1 · Surface-relief grating with patterned refractive index modulation > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2020/0400951 A1 - Document ID: US20200400951A1 - Status: Published application - Kind: A1 - Application number: 16/447,095 - Filed: 2019-06-20 - Published: 2020-12-24 - Earliest claimed: 2019-06-20 - Assignees: Facebook Technologies, LLC - Applicants: Facebook Technologies, LLC - Inventors: Bo Zhang - Web page: https://patentgrep.com/patent/US20200400951A1 ## CPC - G02B 5/1852: {using mechanical means, e.g. ruling with diamond tool, moulding} - G02B 27/0093: {with means for monitoring data relating to the user, e.g. head-tracking, eye-tracking} - B29D 11/0048: {Moulds for lenses (moulds for plastic articles in general B29C33/00)} - B29D 11/00769: {Producing diffraction gratings} - G02B 5/1857: {using exposure or etching means, e.g. holography, photolithography, exposure to electron or ion beams} - G02B 6/0016: {Grooves, prisms, gratings, scattering particles or rough surfaces} - G02B 6/0025: {Diffusing sheet or layer; Prismatic sheet or layer} - G02B 6/0026: {Wavelength selective element, sheet or layer, e.g. filter or grating} - G02B 6/0035: {provided on the surface of the light guide or in the bulk of it} - G02B 6/0065: {Manufacturing aspects; Material aspects} - G02B 27/0172: {characterised by optical features} - B29D 11/00865: {Applying coatings; tinting; colouring (printing, marking or copying processes B41M; identification in general G09F3/00; producing decorative effects in general B44C; positioning or marking of lenses B24B13/0055)} - G02B 2027/0174: {holographic} - G02B 2027/0178: {Eyeglass type (eyeglass details G02C)} - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS - B29D: PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE (making granules B29B9/00; making preforms B29B11/00) ## Abstract Techniques disclosed herein relate generally to surface-relief structures. In one embodiment, a surface-relief grating includes a plurality of grating ridges. The plurality of grating ridges includes a first set of grating ridges characterized by a first refractive index, and a second set of grating ridges interleaved with the first set of grating ridges and characterized by a second refractive index different from the first refractive index. The plurality of grating ridges is imprinted in a polymer layer by a nanoimprint lithography process and is exposed to a light pattern to form the first set of grating ridges and the second set of grating ridges that have different refractive indices. ## Claims ### Claim 1 A method comprising: imprinting, in an organic material layer, a surface-relief structure including a plurality of grating ridges, the organic material layer including a photosensitive base resin that includes monomers; generating a light pattern that includes bright regions and dark regions; and exposing the surface-relief structure to the light pattern to polymerize the monomers in a set of grating ridges of the plurality of grating ridges in the bright regions and increase a refractive index of the set of grating ridges of the plurality of grating ridges in the bright regions. ### Claim 2 (depends on 1) The method of claim 1, wherein an intensity of the light pattern varies in one dimension, two dimensions, or three dimensions. ### Claim 3 (depends on 1) The method of claim 1, wherein generating the light pattern includes: illuminating, by a light beam having a uniform intensity in a cross-section of the light beam, a photomask or a diffractive optical device; or generating an interference pattern using two coherent light beams. ### Claim 4 (depends on 1) The method of claim 1, wherein: the light pattern includes a converging light pattern; and the light pattern has a highest intensity in the set of grating ridges of the plurality of grating ridges in the bright regions. ### Claim 5 (depends on 1) The method of claim 1, further comprising: generating a second light pattern; and exposing the surface-relief structure to the second light pattern. ### Claim 6 (depends on 1) The method of claim 1, further comprising: depositing an overcoat layer on the organic material layer, the overcoat layer filling regions between the plurality of grating ridges and having a refractive index different from the refractive index of the set of grating ridges. ### Claim 7 A surface-relief grating for a display system, the surface-relief grating comprising: a polymer layer including a plurality of grating ridges, wherein the plurality of grating ridges includes: a first set of grating ridges characterized by a first refractive index; and a second set of grating ridges interleaved with the first set of grating ridges and characterized by a second refractive index different from the first refractive index. ### Claim 8 (depends on 7) The surface-relief grating of claim 7, further comprising an overcoat material layer on the polymer layer and filling regions between the plurality of grating ridges. ### Claim 9 (depends on 7) The surface-relief grating of claim 7, wherein the plurality of grating ridges includes a slanted grating ridge. ### Claim 10 (depends on 7) The surface-relief grating of claim 7, wherein the plurality of grating ridges further includes: a third set of grating ridges interleaved with the first set of grating ridges and the second set of grating ridges and characterized by a third refractive index different from the first refractive index and the second refractive index. ### Claim 11 (depends on 7) The surface-relief grating of claim 7, wherein the first set of grating ridges and the second set of grating ridges are distributed in the polymer layer according to a one-dimensional pattern. ### Claim 12 (depends on 7) The surface-relief grating of claim 7, wherein the first set of grating ridges and the second set of grating ridges are distributed in the polymer layer according to a two-dimensional pattern. ### Claim 13 (depends on 7) The surface-relief grating of claim 7, wherein a difference between the first refractive index and the second refractive index is greater than 0.01. ### Claim 14 (depends on 7) The surface-relief grating of claim 7, wherein the polymer layer includes nanoparticles with refractive indices greater than 1.7. ### Claim 15 (depends on 7) The surface-relief grating of claim 7, wherein the plurality of grating ridges is imprinted in the polymer layer by a nanoimprint lithography process. ### Claim 16 (depends on 7) The surface-relief grating of claim 7, wherein the plurality of grating ridges is configured to couple light into or out of a waveguide in the display system. ### Claim 17 A surface-relief grating for coupling light into or out of a waveguide display, the surface-relief grating comprising: a polymer layer including a plurality of grating ridges that includes a first set of grating ridges, wherein: each grating ridge in the first set of grating ridges includes a first layer and a second layer; and the first layer and the second layer have different refractive indices; and an overcoat material layer on the polymer layer and filling regions between the plurality of grating ridges. ### Claim 18 (depends on 17) The surface-relief grating of claim 17, wherein: each grating ridge in the first set of grating ridges includes a plurality of layers that includes the first layer and the second layer; and a refractive index of each grating ridge in the first set of grating ridges is apodized in a direction along a thickness direction of the polymer layer. ### Claim 19 (depends on 17) The surface-relief grating of claim 17, wherein the plurality of grating ridges further comprises a second set of grating ridges interleaved with the first set of grating ridges, wherein the second set of grating ridges is characterized by a refractive index profile different from a refractive index profile of the first set of grating ridges. ### Claim 20 (depends on 17) The surface-relief grating of claim 17, wherein the first set of grating ridges includes a slanted grating ridge.