Linewidth Rebroadening in Quantum Dot Semiconductor Lasers

We investigate the interplay between linewidth and α-factor in quantum dot lasers using experimental data and a minimal quantum dot laser rate equation model. The rebroadening of the laser linewidth found experimentally at high injection currents is explained by analytical means and traced back to nonlinear scattering processes. Important differences of the pump current dependent linewidth evolution of quantum dot lasers are highlighted especially if compared to conventional laser devices. Furthermore, we provide a scheme to extract the amplitude-phase coupling as well as effective carrier scattering rates with standard characterization techniques, i.e., linewidth, light versus injected pump current and modulation response measurements.