Abstract

Noise reduction techniques in photorefractive amplifiers are centrally important for numerous applications in image processing, pattern recognition and detection of ultra-low optical wavefronts. Recently original techniques for reducing the optical noise were proposed and experimentally demonstrated^(1-3). Rotating the crystal is a very general method which successfully removes the amplified scattered noise and the multiple interface parasite reflections. In this paper, we propose an alternative for which no mechanical movement is required. As will detailed in the following, this new noise reduction method is mostly suited to photorefractive materials which exhibit a strong resonance of the two-wave mixing gain around the optimum angle between the injected signal and the pump beam.

© 1991 Optical Society of America