J. Phys. III France
Volume 3, Numéro 7, July 1993
Page(s) 1357 - 1367
DOI: 10.1051/jp3:1993204
J. Phys. III France 3 (1993) 1357-1367

Noise reduction in photorefractive image amplifiers and applications

J.-P. Huignard and H. Rajbenbach

Thomson-CSF, Laboratoire Central de Recherches, Domaine de Corbeville, 91404 Orsay Cedex, France

(Received 20 February 1993, accepted 2 April 1993)

We propose and experimentally demonstrate two original methods for suppressing the beam fanning noise of photorefractive amplifiers. The first one involves two wave mixing in a slowly rotating crystal, while the second requires to tilt the crystal with respect to the recording beams. This method applies to materials which exhibit a sharp resonance of the gain versus the pump-probe beam angle. With both methods a large improvement of the S/N ratio is achieved and virtually noise free image amplifiers are demonstrated. In Bi 12SiO 20, subpicowatt optical signals are detected and amplified. By using combinations of LiNbO 3/Bi 12SiO 20, as storage and amplification crystals respectively a long term readout (more than 20 hours) of a photorefractive memory is achieved.

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