Modulational-induced optical pattern formation in a passive optical-feedback system

Two-dimensional metastable patterns can appear randomly across a broad laser beam profile in a passive optical ring cavity. The instability responsible for pattern formation is primarily modulational in nature, leading to a competitive interaction between strongly saturated solitary-wave ringlike and filamentary spatial structures. The complexity of pattern formation depends sensitively on saturated filament density, which can be conveniently controlled in an optical-feedback arrangement. Our preliminary computational results suggest that the instability domain can be partitioned into two general categories: (1) rapid modulational growth to a single stationary filament or a long-lived metastable pattern involving five filaments growing directly from a shelflike ridge about the central filament or (2) a significantly slower formation of localized filaments forming primarily from a slow modulational growth on fully developed saturated solitary-wave rings. One-dimensional computations with a retarded material response indicate that the general trend of unstable formation should be relatively insensitive to finite retardation effects.