Pattern formation in a nonlinear optical system: the effects of nonlocality

We discuss the role of nonlocal interactions in determining the mechanisms of pattern formation and selection in a nonlinear system formed by a Liquid Crystal Light Valve inserted in an optical feedback loop. We present experimental results, and compare them with the predictions of a linear stability analysis of the equations governing the system. Nonlocality is introduced in the system via a lateral transport of a length ?x of the feedback signal. The value of the transport length plays a key role in determining the symmetry of the selected pattern in systems with both focusing and defocusing nonlinearity. In the defocusing case, the spatial wavelength of the pattern is also affected by the value of the transport length.