Stabilization, manipulation and control of transverse optical patterns in a photorefractive feedback system

We present an experimental realization of an almost non-invasive stabilizat ion and manipulation method of coexisting and unstable states of pattern fo rming systems. In a photorefractive single feedback system, a control path; is:used to realize amplitude and phase-sensitive Fourier-plane filtering, u tilizing only a few per cent of the system's intensity. By that means, we w ere able to stabilize desired but not predominantly excited patterns in par ameter space regions where several patterns are present as coexisting or un derlying solutions. Changing the phase of the control signal allows one to switch between different pattern states.