Epitaxial structure dependence of the linewidth enhancement factor in GaAs and InGaAs quantum well lasers

The linewidth enhancement factor, alpha, plays a key role in our ability to obtain spatially coherent output from high-power semiconductor lasers and amplifiers. To obtain alpha values, modal gain and carrier-induced refractive index change have been measured in broad-area quantum well epitaxial structures with various well depths, widths, and compositions as functions of current density.