@InProceedings{Supelec586,
author = {Nicolas Marsal and Delphine Wolfersberger and Marc Sciamanna and Germano Montemezzani},
title = {{Advection effect in a photorefractive single feedback system: from noise- to dynamics- sustained instabilities}},
year = {2010},
booktitle = {{Proceedings of SPIE}},
volume = {7728},
month = {apr},
address = {Bruxelles (Belgique)},
abstract = {Systems in which intrinsic noise is amplified so that it influences the system itself provide a way to probe and characterize noise. In this work, we study the effect of advection on an optical single feedback system displaying patterns. This advection, occurring when the angle of the optical pump beam is not zero gives rise to the so called convective noise- and absolute dynamics- sustained instabilities. The convective regime, where no pattern is expected, can show structures or patterns if noise is present in the system. Macroscopic noise-sustained structures can be formed resulting from the amplification in preferential direction of the perturbations produced by the microscopic noise. In contrast, in the absolute regime the resulting optical pattern is sustained by the drifting dynamics created by the advection. Despite the large theoretical interest and recent experimental demonstrations using a Kerr-type nonlinearity, an experimental evidence of an advection effect on the dynamics of the pattern formation process in a photorefractive system is still lacking. We investigate experimentally and numerically the dynamics of pattern excitation in presence of a tilted nonlinear photorefractive single feedback system. By varying the angle of the feedback mirror, thus breaking the inversion symmetry in the system, we show that this advection effect causes the existence of: (i) a transition from convective to absolute instabilities, (ii) the formation of new pattern geometries, (iii) the seeding of noise-sustained structures. To the best of our knowledge, this last result is experimentally observed for the first time in an optical system. }
}