Space-Time Chaos Characterization in a Non-linear Optical Feedback Loop

Abstract

We present an experimental setup that provides the possibility to easily explore different kind of space‐time chaos. This allows to extract and compare the relevant features of each of them, so as to further develop efficient adaptated control strategies. The system is an optical feedback loop closed through a Kerr‐like non‐linear medium (liquid crystal light valve). Beyond a critical value of the input light intensity (forcing), transverse instabilities develop in the optical beam. It results in the formation of out‐of‐equilibrium patterns, whose properties depend on various parameters that can be varied (translated or rotated feedback; focusing or defocusing non‐linearity; relative amount of diffraction and interferences, etc). Most of the time, the pattern at threshold is asymptotically stationary, after a diffusive transient. At higher forcing, patterns become non‐stationary, and defects are usually created and annihilated continuously, giving rise to a space‐time chaos regime. At even higher forcing,...