Experimental determination of multiple instability regions by Fourier filtering methods in a single-mirror feedback scheme

Summary form only given. Considerable interest emerged in controlling the spatial structures arising spontaneously in nonlinear optical systems by Fourier filtering techniques. In this contribution we utilize a special Fourier filtering scheme to give an experimental demonstration of a basic property of many optical pattern forming systems. This is the existence of a sequence of multiple, tonguelike instability regions at increasing values of transverse wave numbers and a quantitative measurement of their boundaries. The results indicate the origin of a secondary instability in the system without filter occurring far beyond threshold. Also the importance of incorporating finite size effects in the theoretical description for a proper determination of the threshold is demonstrated.