A comprehensive model is presented to study filamentation in both conventional double heterostructure (DH) and quantum well (QW) semiconductor lasers. The spatial dynamics of broad-area (BA) semiconductor lasers is studied by numerically solving space-dependent coupled partial differential equations for the complex optical fields and the carrier density distribution. A self-consistent iteration is developed to model the formation and longitudinal propagation of unstable transverse optical filamentary structures by means of beam propagation method. The effects of stripe width, linewidth enhancement factor and Kerr coefficient are analyzed. © 2006 IEEE.