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A method based on Fourier filtered control signals for stabilization of unstable patterns in a nonlinear optical single feedback system is experimentally realized. The successful stabilization of the homogeneous solution and different stationary periodic patterns far above the pattern forming threshold as well as the elimination of spatiotemporal disorder above a secondary instability has been achieved. The temporal evolution of the control signal verifies the underlying philosophy of noninvasive control that changes only the linear stability of the systems' solution and not the solution itself.

We report on the addressing and control of the lateral positions of optical spatial solitary structures in a single feedback experiment with a saturable Kerr nonlinearity. Solitary structures allow a locally self-confined switching between a dark background and a bright state. This binary character can be of use to all-optically route information in optical networks. In general the lateral positions of solitary structures are strongly influenced by mutual interactions and system inhomogeneities. For potential photonic applications these interactions must be controllable. Therefore a noninvasive interferometric control method based on spatial Fourier filtering is studied in order to position solitary structures. Numerical and experimental results show that solitary structures can be aligned to periodic grids of different scale with hexagonal or square geometries.

A nonlinear optical system, which spontaneously forms hexagonal patterns, is exposed to a weak, spatially modulated forcing. As forcing, stationary hexagonal patterns are used under variation of their transverse wave number. In the experiment, we observe a locking when the forcing wave number is close to one of the critical wave numbers of the unforced system. Outside the locking regimes, forcing provokes spatiotemporal disorder. The system response is characterized quantitatively with respect to its dynamics and to its spatial order.

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