Self-organized pattern formation in optical feedback systems
Hexagonal pattern formation in a LCLV in the near and far field
The spontaneous selforganized generation of spatial structures in systems far out of thermodynamic equilibrium is a current and interdisciplinary research field. Strongly related cooperative phenomena in microscopically completely different systems are investigated and modelled throughout diverse scientific disciplines. Optical feedback systems in which laser beams interact with nonlinear media such as liquid crystals or solids (e.g. photorefractive crystals) display emergent phenomena of selforganization such as regular patterns, localized states, or even spatial and temporal chaos, if the system is driven beyond a characteristic threshold. The generation of self-organized phenomena is governed by general laws that we investigate using the photorefractive nonlinearity and the optically adressable liquid crystal light valve as model systems in experiment, computational experiments and analytical modelling.
In addition to the fundamental knowledge on chaotic and selforganized phenomena that can be obtained by investigating these model systems, such phenomena are promising candidates for future optical information processing. A precondition to any application is the development of control techniques in order to deterministically address and manipulate specific states of the investigated systems. In systems providing a nonlinear refractive index modification, we therefore investigate the control and manipulation of selforganizes transverse patterns. To that end, we vary the input and feedback systematically and dynamically in the transverse plane, using methods such as spatial frequency filtering, optical control signals, dynamic incoherence and stochastic resonance.