Abstract

We investigate the formation of square, rectangular or squeezed hexagonal patterns in a photorefraetive single-feedback experiment. Although in general, hexagonal patterns are predominantly excited in these systems, non-hexagonal patterns may be stable in a certain range of the propagation length. Moreover, a coexistence of two hexagons with two different transverse scales is found and explained by the results of a linear stability analysis. To achieve control of these patterns, we introduce a two-arm feedback system with a Fourier filter in one arm and present results on the stabilization of roll and square pattern in a parameter region where the hexagonal pattern is the only output without control.

© 1999 Optical Society of America