Journal of the European Optical Society B: Quantum and Semiclasical Optics, 1, 191-197 (1999).
Pattern formation in nonlinear optical cavities, when an advection-like term is present, is analyzed. This term breaks the space inversion symmetry causing the existence of a regime of convective instabilities, where noise-sustained structures can be found, and changing the pattern orientation and the selected wavevector. The concepts of convective and absolute instability, noise-sustained structures and the selection mechanisms in two dimensions are discussed in the case of the optical parametric oscillators and a Kerr resonators. In the latter case, in which hexagons are the selected structure we predict and observe that stripes are the most unstable structures in the initial linear transient. In the nonlinear regime of the absolute instability these stripes destabilize and hexagons form. Their orientation is dictated by that of the transient stripes and therefore by the advection term. In the convective regime we predict and observe disordered noise-sustained hexagons, preceded in space by noise sustained stripes.
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Pere Colet e-mail: [email protected] http://www.imedea.uib.es/~pere/