# US 5,348,688 A · Optical power limiters and materials therein

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- Number: US 5,348,688 A
- Document ID: US5348688A
- Status: Granted
- Kind: A
- Application number: 06/700,995
- Filed: 1984-12-17
- Granted: 1994-09-20
- Earliest claimed: 1984-12-17
- Assignees: The United States of America as represented by the Secretary of the Army
- Inventors: Edward J. Sharp; Gary L. Wood; Richard R. Shurtz, II; Juergen L. W. Pohlmann
- Web page: https://patentgrep.com/patent/US5348688A

## CPC

- G02F 1/3511: {Self-focusing or self-trapping of light; Light-induced birefringence; Induced optical Kerr-effect}
- C09K 19/60: Pleochroic dyes
- G02F 1/361: Organic materials
- 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
- C09K: MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE

## Abstract

A liquid crystal modified by the addition of an organic dye is used as a non-linear optical material in two devices which limit the optical radiations to sensitive photodetectors. One device uses the self-focusing induced in the crystal to disperse high-intensity optical radiation, the other uses the change of index of refraction of the crystal to effect total reflection of high-intensity radiation from a liquid crystal-linear optical material inter-face

## Claims

### Claim 1

An optical power limiter for protecting a photodetector from high-power optical radiations, including at least a substantially transparent non-linear optical material whose index of refraction is responsive both to wavelength and to optical power of incident radiation, wherein said material is a nematic liquid crystal with a dye dissolved therein, whereby said dye enhances the index-of-refraction response of said liquid crystal to the wavelengths of said high-power optical radiation; additionally including a linear optical material having a surface in intimate contact at a planar interface with a surface of said nonlinear optical material, and means for directing incident radiation into said nonlinear material toward said photodetector and onto said interface at an angle for total reflection of said high-power optical radiations when the index of refraction of said nonlinear optical material changes in response to said high-power radiation, whereby said high-power optical radiations are self-focussing in said material and totally reflect at said interface to protect said photodetector, and other incident radiation is not self focussing, and is not totally reflected, but freely passes to said photo-detector.