Modeling of gain recovery of quantum cascade lasers

We present a model to calculate the gain recovery of quantum cascade lasers (QCLs). We implement the model for two QCLs with different material systems and quantum mechanical designs. It is found that both incoherent scattering and coherent tunneling are important for gain recovery, however, their relative importance depends on the material systems, quantum mechanical designs, and operating conditions. Though details of the gain recovery vary for the two QCLs, a complete gain recovery takes similar to 2 ps in both cases. The results are consistent with the results found in pump-probe experiments. (C) 2011 American Institute of Physics. [doi:10.1063/1.3544201]