Nonequilibrium laser dynamics of quantum-dot lasers with optical feedback and injection

Abstract

Summary form only given. Quantum-dot (QD) laser devices offer a variety of advantages over conventional quantum-well (QW) lasers due to their low threshold currents and their high temperature stability. In general, QD lasers show strongly damped relaxation oscillations, due to the charge carrier scattering between the QD and off-resonant reservoir states in the device, which leads to less complicated dynamics under optical feedback and optical injection when compared to QW or bulk lasers. The charge carriers influence both the gain and the refractive index of the active region, which leads to the amplitude-phase coupling, commonly characterized by the linewidth enhancement factor α. This coupling is widely assumed to be small for QD lasers, leading to α-factors on the order of ~1. However, the use of an α-factor in QD lasers has been controversially discussed, and it was shown that the QD laser dynamics can not be accurately described by using an α-factor. We employ a QD laser model, which describes the carrier dynamics in the inhomogeneously broadened QD ensemble as well as the carrier dynamics in the 2D QW, including carrier heating effects and microscopically calculated nonlinear scattering rates between QD and QW states, to calculate the QD laser dynamics under external optical injection and optical feedback without the need to introduce an α-factor.