RELATIONS BETWEEN SPONTANEOUSLY OCCURRING BEAMS IN BISMUTH SILICON-OXIDE WITH 2 FREQUENCY-DETUNED PUMP BEAMS

We report strong competition of intensities between spontaneously emer ging beams (subharmonics) and other diffracted beams in two-wave mixin g experiments with two frequency-detuned pump beams in photorefractive bismuth silicon oxide. The measurements show that the onset of subhar monics strongly affects the strength of the fundamental component of t he primary grating, which caused the subharmonics in the first place. Suppression of subharmonics by vibration of the crystal increased the diffraction efficiency of the fundamental grating component by more th an an order of magnitude. (C) 1995 Optical Society of America