Optical pattern selection by a lateral wave-front shift

Nonlocal effect on vortex-induced pattern dynamics

We show experimentally and theoretically that the interplay between a vortex-induced pattern rotation and an optical feedback nonlocality-induced pattern drift leads to new dynamics and geometries of optical pattern formation. First, the vortex-induced pattern rotation and the nonlocality-induced drift can annihilate each other, resulting in the formation of static zones in the near field of the otherwise drifting pattern. Second, increasing the external mirror tilt leads to new pattern solutions that are composed of wave vectors of different amplitudes and directions, resulting in a multistriped pattern geometry.

Effects of translational coupling on dissipative localized states

Nonequilibrium localized states under the influence of translational coupling are studied experimentally and theoretically. We show that localized structures are deformed and advected in the direction of the coupling, thus undergoing different instabilities. Experimentally, localized structures are obtained in a light valve with optical feedback. By introducing a tilt of one mirror in the feedback loop, localized structures acquire a translational coupling. To understand the phenomenon in a universal framework we consider a prototypical model of localized states with translational coupling in one and two spatial dimensions. The model allows us to analytically characterize the propagation speed and the deformation exhibited by the localized state profiles as well as to figure out different mechanisms of destabilization of these dissipative structures. The results are in good qualitative agreement with the experimental and numerical observations.

Vortex emission accompanies the advection of optical localized structures

We show that the advection of optical localized structures is accompanied by the emission of vortices, with phase singularities appearing in the wake of the drifting structure. Localized structures are obtained in a light-valve experiment and made to drift by a mirror tilt in the feedback loop. Pairs of oppositely charged vortices are detected for small drifts, whereas for large drifts a vortex array develops. Observations are supported by numerical simulations and linear stability analysis of the system equations and are expected to be generic for a large class of translated optical patterns.

Domain segregation in a two-dimensional system in the presence of drift

Motivated by experiments on optical patterns we analyze two-dimensional extended bistable systems with drift after a quench above threshold. The evolution can be separated into successive stages: linear growth and diffusion, coarsening, and transport, leading finally to a quasi-one-dimensional kink-antikink state. The phenomenon is general and occurs when the bistability relates to uniform phases or two different patterns.