Noise suppression in photorefractive image amplifiers.

We propose and experimentally demonstrate a simple technique capable of significantly enhancing the signal-to-noise ratio of photorefractive amplifiers. The optical noise due to amplified scattered light and multiple interface reflections is removed by performing two-wave mixing in off-axis-rotating BaTiO(3) and Bi(12)SiO(20) crystals. A 20-fold improvement of the signal-to-noise ratio is achieved, and virtually noise-free image amplifiers are demonstrated.