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Q: Quantenoptik
Q 16: Nonlinear Optics II
Q 16.4: Talk
Tuesday, April 3, 2001, 18:15–18:30, H 2013
Self-organization and Fourier-Control of transverse patterns in photorefractive wave mixing with a single feedback mirror — •Oliver Sandfuchs1, Milivoj R. Belic2, and Friedemann Kaiser1 — 1Institut für Angewandte Physik, Nichtlineare Dynamik - Theorie, Hochschulstrasse 4a, TU-Darmstadt, 64289 Darmstadt, GERMANY — 2Institute of Physics, P.O. Box 57, 11001 Belgrade, Yugoslavia
Counterpropagation of two optical beams is known to lead to transverse spatiotemporal structures. We theoretically investigate the spontaneous formation and the control of spatiotemporal patterns in photorefractive wave mixing (PRWM) with a single feedback mirror in 1 and 2 dimensions. Following experimental observations of the last 5 years, for the first time numerical results succeeded in displaying spatiotemporal structures in this system. Hexagonal structures dominate near onset, squares and stripes have also been identified applying Fourier-control techniques. The formation and stabilization process of the patterns out of the initial linearly unstable annulus of active modes is shown. Analytically we derive an amplitude equations of the Ginzburg-Landau-dodecagon-type taking into account the pump depletion, which is present in PRWM and results in longitudinal eigenmodes as tranverse modes are built through the volume index grating, aiming at the stability and coexistence of the different 2D-planforms. The existence of stripe-hexagon and square-hexagon competition is predicted and discussed, and above threshold dodecagonal structures exist.