NONLINEAR MECHANISMS OF FILAMENTATION IN BROAD-AREA SEMICONDUCTOR-LASERS

There are three nonlinear mechanisms that can lead to filamentation in broad-area semiconductor lasers: gain-saturation-induced changes in t he refractive index through the linewidth-enhancement factor, self-foc using due to heat-induced index changes, and self-defocusing through i ntensity-dependent index changes in the cladding layer, We present a t heoretical model to analyze these mechanisms and their relative roles in destabilizing the laser output, We find that there exists a critica l value for the linewidth-enhancement factor below which broad-area la sers are stable for wide stripe widths (as wide as 250 mu m) and high pumping levels (as high as 20 times threshold), We also find that broa d-area lasers are less susceptible to filamentation through self-defoc using and show how an intensity-dependent index in the cladding layer may be used to suppress filamentation caused by the linewidth-enhancem ent factor.