SPATIAL PATTERNS IN NONLINEAR OPTICS Pattern Formation in Optical Cavities With Incoherent Light

terns of this non-resonant system exhibit spatial line narrowing with the increase of feedback, resembling the line narrowing in (resonant) lasers (see Fig. 1). In fact, despite the incoherence of the light, this cavity threshold is analogous to many thresholds in resonant feedback systems with gain.1 In a subsequent paper, we theoretically analyzed a cavity in which the light was also spatially incoherent.4 The pattern formation process in such a cavity is always associated with two consecutive thresholds of different character. The first threshold is the point at which the uniform intensity beam becomes unstable as the nonlinearity overcomes the diffusive tendency of spatially incoherent light. In marked contrast to what occurs in coherent cavities, this threshold is independent of the cavity boundary conditions. The second threshold is the aforementioned “cavity threshold.” These theoretical results have recently been confirmed experimentally. In conclusion, we have summarized features of optical pattern formation that result from the interplay between the statistical (coherence) properties of light, the nonlinearity of the medium and the feedback of the cavity. These results open SPATIAL PATTERNS IN NONLINEAR OPTICS