Dynamic Response Analysis of External Cavity Quantum Cascade Lasers Using Equivalent Circuit Model

An equivalent circuit model is developed for external-cavity quantum cascade lasers (EC-QCLs) from the carrier and photon rate equations including both the Fabry-Perot (FP) and EC optical modes. In the pulse-mode operation, the model accurately predicts the mode competition between the FP and EC optical modes at the beginning of each pulse, which is in good agreement with experiment. Additionally, the results show that the EC- mode is the dominant optical mode at the end of injected current pulse due to the longer round trip time of the EC mode.