Patterns, fronts and structures in a Liquid-Crystal-Light-Valve with optical feedback

The basic mechanisms of optical pattern formation are reviewed, with particular reference to a system based on a Liquid-Crystal-Light-Valve with optical feedback. The system is described in different configurations, corresponding to the experiments that have led to the most fascinating observations, such as the optical crystals and quasi-crystals, the geometrical frustration leading to domain coexistence and competition, the super-lattices characterized by couplings of different wave vectors at different lengths and orientations. The purely diffractive and purely interferential cases are discussed separately, in such a way to outline the main features of the two types of optical feedback and to give a better understanding of the complex behaviors observed when both are simultaneously present. The role of nonlocality in the optical feedback loop, such as rotation or drift, is put into evidence, showing how this parameter drives the symmetry selection in the pattern-forming process. (etc)