Vortex dynamics of counterpropagting laser beams in photorefractive materials
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We study vortex patterns of counterpropagating laser beams in a photorefractive crystal, with or without the background photonic lattice. The vortices are effectively planar and have two “flavors” because there are two opposite directions of beam propagation. In a certain parameter range, the vortices form stable equilibrium configurations which we study using the methods of statistical field theory and generalize the Berezinsky–Kosterlitz–Thouless transition of the XY model to the “two-flavor” case. In the nonequilibrium regime, the patterns exhibit an Andronov–Hopf bifurcation which may lead to oscillations (limit cycle), chaos or decay to zero intensity due to radiation losses. We show how to identify various pathways toward instability from intensity patterns, i.e. from experiment.
KeywordsVortex BKT transition Photorefractive optics Statistical field theory
Work at the Institute of Physics is funded by Ministry of Education, Science and Technological Development, under Grants Nos. OI171033 and OI171017. M.P. is also supported by the NPRP 8-028-1-001 project of the Qatar National Research Fund (a member of the Qatar Foundation).
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