Transport Induced Pattern Selection in a Nonlinear Optical System

The pattern selection process in a two-dimensional optical system, with a Kerr nonlinearity inserted in an optical feedback loop, is strongly affected by nonlocal interactions. Experimentally, nonlocality is introduced by means of a lateral transport of the feedback signal. As the transport length is increased, the system displays a sequence of transition over different classes of patterns. In the case of purely diffractive feedback, patterns corresponding to both focusing and defocusing nonlinearities are reported. When interference instead of diffraction operates in the feedback loop, new selection rules govern both the scale and the spatial symmetry of the observed structures. In all the cases considered, the stability analysis of the model equations yields theoretical predictions in good agreement with the experimental results.