Performance Optimization and Instability Study in Ring Cavity Quantum Cascade Lasers

An optimization study of quantum cascade lasers (QCLs) considering the laser instability condition is performed. To model current transport, the Pauli master equation is solved using a Monte Carlo approach. The effects of saturable absorber and pumping strength on the instability threshold are investigated. A particle swarm optimization algorithm is applied to increase the laser optical gain. A large optical gain below the instability threshold is achieved for optimized QCL designs. To analyze the optimized structure, a numerical calculation based on the Maxwell-Bloch equations is performed. The results indicate side-mode instabilities due to Risken-Nummedal-Graham-Haken-like instability.