THRESHOLD FOR PATTERN-FORMATION IN A MEDIUM WITH A LOCAL PHOTOREFRACTIVE RESPONSE

Threshold equations for the instability of counterpropagating waves ag ainst spontaneous initiation of small-angle light patterns are analyze d for a medium with a local photorefractive response and various bound ary conditions. These equations take into account all actual contribut ions to the reflection phase gratings. The form of the threshold equat ion is directly related to the spatial symmetry of the problem. We stu dy the dependence of the threshold thickness of the crystal and the an gle of light emission on experimentally controllable parameters and di scuss the prospects for experimental studies of pattern formation in L iNbO3 crystals. (C) 1997 Optical Society of America.