Patent
1987-06-19
1988-08-09
Miller, Stanley D.
350342, 350347E, 350347V, G02F 113
Patent
active
047623977
ABSTRACT:
Apparatus is disclosed for phase conjugation of an input beam with thresholding of spatially resolvable parts of the beam that have amplitudes greater than a predetermined threshold value. A phase conjugation reflector produces a phase conjugated replica of a specularly reflected and thresholded portion of the input beam, which is retroreflected toward the source of the input beam. All of the spatial components of the phase conjugated replica retain the same relative phase relationships with respect to each other as the incident complex beam. In a preferred embodiment the invention comprises a liquid crystal light valve (LCLV) system, input and output polarizers, and a phase conjugate mirror (PCM). This combination of elements forms a device that can function as a threshold retroreflector with .about.10.sup.6 resolvable elements. Thresholding is accomplished by allowing part of each spatially resolvable component to reach the photoconductive layer on the opposite side of the LCLV dielectric mirror that reflects the component. The dielectric mirror can be made partially transmissive, or an optical feedback path can be provided to convey a portion of each spatially resolvable component to the photoconductive layer behind the point of reflection by the dielectric mirror. Various feedback methods are presented. The phase conjugate mirror can be implemented by means of any of the phenomena which give rise to phase conjugate retroreflection, such as stimulated scattering, stimulated photorefraction, three-wave mixing, or four-wave mixing.
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Duraiswamy V. D.
Gallivan Richard
Hughes Aircraft Company
Karambelas A. W.
Miller Stanley D.
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