SPATIOTEMPORAL PATTERN-FORMATION IN COUNTERPROPAGATING 2-WAVE MIXING WITH AN EXTERNALLY APPLIED-FIELD

The spatiotemporal dynamics of two counterpropagating beams in a photo refractive crystal with nonlocal and sluggish response is investigated in the longitudinal and one transverse dimension. A static external e lectric field is applied to the crystal to control the coupling streng th of the two-wave mixing process. A nonautonomous linear stability an alysis is performed that takes a nonconstant modulation depth into acc ount. The onset of pattern formation for arbitrary coupling constants and pump ratios and the influence of linear absorption are discussed. Above the threshold predicted by stability analysis, running transvers e waves appear in the optical near field and wandering spots appear in the corresponding far field. A nonlinear eigenmode analysis reveals t he running transverse waves as secondary instabilities. (C) 1998 Optic al Society of America.