Filamentation and linewidth enhancement factor in InGaAs quantum dot lasers

We report measurements of the near-field of broad-area lasers with quantum dot and quantum well active regions designed to emit at 1 μm. The quantum dot devices exhibit less filamentation than comparable quantum well devices, and exhibit a reduction in filamentation as the injection level is increased. This is consistent with a theory that includes the Coulomb coupling between dot and wetting-layer states on a microscopic level. The theory predicts a linewidth enhancement factor from −3 to 1, depending on carrier density and inhomogeneous broadening.