HIGH-GAIN, LOW-NOISE SIGNAL BEAM AMPLIFICATION IN PHOTOREFRACTIVE BATIO3

We describe a pulse readout technique for high gain and a high signal-to-noise ratio (SNR) in signal beam amplification by two-beam coupling in a photorefractive BaTiO3 crystal. The basic idea behind the technique is the formation of photorefractive gratings using a low-intensity pump beam and subsequent readout of this grating with a strong pulse for a duration that is less than the time constant for noise development or beam fanning. Large values (approximately 11,000) of the signal beam gain and SNR's of approximately 1300 are achieved. A noise-free image amplification is the main achievemement of this technique.