Manipulation, stabilization, and control of pattern formation using Fourier space filtering

We present an experimental realization of an almost noninvasive stabilization and manipulation method of coexisting and underlying states of pattern forming systems. In a photorefractive single feedback system, a ring control path is used to realize amplitude and phase-sensitive Fourier-plane filtering, utilizing only a few percent of the system's intensity. We were able to stabilize desired but not predominantly excited patterns in parameter space regions where several patterns are present as underlying solutions. By positive (in-phase) and negative (out-of-phase) control, rolls could be excited in parameter regions where hexagonal structures are preferably stable.