Düsseldorf 2007 – wissenschaftliches Programm

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Q: Fachverband Quantenoptik und Photonik

Q 15: Nichtlineare optische Effekte und Lichtquellen III

Q 15.5: Vortrag

Montag, 19. März 2007, 17:30–17:45, 5J

Control of self-organized patterns in a photorefractive single feedback system by seeding — •Nicoletta Brauckmann, Philip Jander, and Cornelia Denz — Institut für Angewandte Physik and Center for Nonlinear Science, Westfälische Wilhelms-Universität, Corrensstraße 2, 48149 Münster, Germany

The photorefractive single feedback system is known to show a rich variety of transverse patterns (hexagonal patterns, squeezed hexagons, rectangles and rhombohedrons). Different temporal and spatial control approaches, such as pattern manipulation by frequency detuning or pattern selection by Fourier control, turned out to be powerful techniques of pattern control. In this contribution, we consider direct control of pattern formation by seeding the pump beam with patterns of selectable contrast, orientation, scale and symmetry via a liquid crystal amplitude light modulator. In addition to generating new system solutions, the addressing of states which are already stable or unstable fix points is of special interest. In these cases, we can realize an adaptive control scheme, where the control signal is diminished as the system approaches the desired state. The remaining control signal level is only needed to counter noise-induced fluctuations, and thus can be used as a measure of the impact of noise on the stability of different patterned states. Beyond seeding the system with a single pattern, we prestructure the pump beam with domains of different symmetries and scale in order to observe induced competition between the addressed patterns.