# US 2021/0240032 A1 · Improvements in and relating to optical elements > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2021/0240032 A1 - Document ID: US20210240032A1 - Status: Published application - Kind: A1 - Application number: 17/255,903 - Filed: 2019-06-27 - Published: 2021-08-05 - Earliest claimed: 2018-06-27 - Assignees: Merck Patent GmbH - Applicants: Merck Patent GmbH - Inventors: John Clifford JONES; Markus WAHLE - Web page: https://patentgrep.com/patent/US20210240032A1 ## CPC - G02F 1/133371: {Cells with varying thickness of the liquid crystal layer} - G02F 1/29: for the control of the position or the direction of light beams, i.e. deflection - G02F 1/134309: {characterised by their geometrical arrangement} - G02F 1/294: {Variable focal length devices} - G02F 2203/06: Polarisation independent - G02F: OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS ## Abstract An electrically switchable optical modulator for modulating an optical wavefront transmitted therethrough, comprising a birefringent first optical element and a birefringent second optical element each having respective ordinary and extraordinary refractive indices. A birefringent liquid crystal material is sandwiched between the first and second optical elements. The extraordinary refractive index of the liquid crystal material is electrically switchable between: a first state in which it has a first value; and, a second state in which it has a second value different from the first value. One or both of the first value and the second value is un-matched to the extraordinary refractive index of the first optical element in respect of light polarised in a first direction of linear polarisation, and is un-matched to the extraordinary refractive index of the second optical element in respect of light polarised in a second direction of linear polarisation orthogonal to the first direction. This switchably renders a relative contrast in extraordinary refractive index as between the liquid crystal material and the first and second optical elements for modulating said wavefront. ## Claims ### Claim 1 An electrically switchable optical modulator for modulating an optical wavefront transmitted therethrough, comprising: a birefringent first optical element and a birefringent second optical element each having respective ordinary and extraordinary refractive indices; a birefringent liquid crystal material sandwiched between the first and second optical elements; wherein the extraordinary refractive index of the liquid crystal material is electrically switchable between: a first state in which it has a first value; and, a second state in which it has a second value different from the first value; wherein one or both of the first value and the second value is un-matched to the extraordinary refractive index of the first optical element in respect of light polarised in a first direction of linear polarisation, and is un-matched to the extraordinary refractive index of the second optical element in respect of light polarised in a second direction of linear polarisation orthogonal to the first direction, thereby to switchably render a relative contrast in extraordinary refractive index as between the liquid crystal material and the first and second optical elements for modulating said wavefront. ### Claim 2 (depends on 1) An electrically switchable optical modulator according to claim 1 wherein the first value is matched to the respective extraordinary refractive indices of both the first and second optical elements. ### Claim 3 (depends on 1) An electrically switchable optical modulator according to claim 1 wherein the ordinary refractive index of the liquid crystal material is matched to the respective ordinary refractive indices of both the first and second optical elements. ### Claim 4 (depends on 1) An electrically switchable optical modulator according to claim 1 in which the first and second optical elements are formed from a birefringent polymer and define a director, wherein the director of the first optical element is transverse to the director of the second optical element. ### Claim 5 (depends on 1) An electrically switchable optical modulator according to claim 1 in which the first and second optical elements are formed from a reactive mesogen cured from a reactive state to form a birefringent polymer. ### Claim 6 (depends on 2) An electrically switchable optical modulator according to claim 2 in which the liquid crystal material has a twisted nematic liquid crystal arrangement whereby when in said first state the optic axis of the liquid crystal material: is aligned substantially parallel to the director of the first optical element; and, is aligned substantially parallel to the director of the second optical element. ### Claim 7 (depends on 1) An electrically switchable optical modulator according to claim 1 in which one or each of the first and second optical elements presents a curved surface to which said liquid crystal material complies. ### Claim 8 (depends on 1) An electrically switchable optical modulator according to claim 1 in which one or each of the first and second optical elements presents a surface relief pattern to which said liquid crystal material complies. ### Claim 9 (depends on 8) An electrically switchable optical modulator according to claim 8 in which each of the first and second optical elements presents a surface relief pattern to which said liquid crystal material complies, wherein the pattern presented by the first optical element is the reciprocal of the pattern presented by the second optical element. ### Claim 10 (depends on 7) An electrically switchable optical modulator according to claim 7 in which each of the first and second optical elements presents a surface relief pattern to which said liquid crystal material complies, wherein the pattern presented by the first optical element is substantially the same as the pattern presented by the second optical element. ### Claim 11 (depends on 1) An electrically switchable optical modulator according to claim 1 in which the first optical element opposes the second optical element. ### Claim 12 (depends on 1) An electrically switchable optical modulator according to claim 1 in which the first optical element defines a first optical axis and the second optical element defines a second optical which is substantially coaxial with the first optical axis. ### Claim 13 (depends on 1) An electrically switchable optical modulator according to claim 1 wherein the liquid crystal material is disposed between two separate electrodes configured to support between them an electrical field for switching the extraordinary refractive index of the liquid crystal material from said first state to said second state. ### Claim 14 (depends on 13) An electrically switchable optical modulator according to claim 13 wherein one or each of the first optical element and the second optical element is disposed between the two separate electrodes. ### Claim 15 (depends on 13) An electrically switchable optical modulator according to claim 13 wherein one of the two separate electrodes is disposed between the first optical element and the liquid crystal material. ### Claim 16 (depends on 13) An electrically switchable optical modulator according to claim 13 wherein one of the two separate electrodes is disposed between the second optical element and the liquid crystal material. ### Claim 17 (depends on 1) An electrically switchable optical modulator according to claim 1 where one or both of the optical elements is shaped to define an axis of cylindrical symmetry which is substantially perpendicular to a flat surface disposed on one side of the respective optical element. ### Claim 18 (depends on 17) An electrically switchable optical modulator according to claim 17 wherein both of the optical elements are shaped to define a respective said axis of cylindrical symmetry and the axis of cylindrical symmetry of the first and second optical elements are coaxial. ### Claim 19 A method of manufacturing an optical modulator comprising one or more birefringent optical elements shaped to a desired shape for modulating an optical wavefront transmitted therethrough, wherein each birefringent optical element is provided according to a method including: providing a flexible sheet presenting an embossing surface embossed with shape which is reciprocal to said desired shape; providing a quantity of a reactive mesogen material in an uncured state upon a surface of a substrate; flexing the embossing surface to press against the quantity of reactive mesogen material progressively across a surface of the quantity of reactive mesogen material thereby to form a shaped birefringent part possessing said desired shape; curing the shaped birefringent part to form said birefringent optical element. ### Claim 20 (depends on 19) A method of manufacturing an optical modulator according to claim 19 in which the optical modulator is electrically switchable. ### Claim 21 (depends on 20) A method of manufacturing an optical modulator according to claim 20 comprising an electrically switchable liquid crystal material sandwiched between two said birefringent optical elements. ### Claim 22 (depends on 19) A method according to claim 19 including providing a preferential surface alignment to the embossing surface and therewith imparting the preferential surface alignment to the embossed surface of the shaped birefringent part, the surface alignment being configured to align said liquid crystal material.