Controlled optical structures in a nonlinear system involving the suppression of low spatial frequencies in the feedback loop

A nonlinear optical system with spatially distributed feedback was studied both theoretically and experimentally. The phase-to-intensity transformation in this system was performed by a spatial filter capable of suppressing low spatial frequencies. Hard excitation of stationary spatial structures observed in this system was explained by an analysis of the phase space structure of the amplitude equations. The developed theoretical approach, which uses a step-function approximation of the steady-state solution, allows one to determine the main quantitative characteristics of the generated structures. The basic properties of the response of the system to external perturbations with various symmetries were investigated experimentally. The obtained experimental data qualitatively agree with the results of the theoretical analysis.