Optical power limiters and materials therein

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.