Increasing Stability by Two-State Lasing in Quantum Dot Lasers with Optical Injection

A quantum dot (QD) laser capable of two-state lasing in certain parameter regions is studied under external optical injection. Our modeling approach is based on microscopically based rate equations, which include carrier dependent index shifts obtained from a full Bloch-equation approach. Our results show an increase of the dynamical stability of the two-state QD laser under optical perturbations if compared to a single-state QD laser, e.g. to a QD laser with high losses in the excited state. Chaotic dynamics predicted for single-state QD lasers under strong and detuned injection completely vanishes if excited state lasing is possible. This suggests a general trend for semiconductor lasers to yield an improved stability against optical perturbations with more dynamical degrees of freedom.