Relaxation kinetics in quantum cascade lasers

Relaxation kinetics in a quantum cascade intersubband laser are investigate d. Distribution functions and gain spectra of a three-subband double-quantu m-well active region are obtained as a function of temperature and injectio n current. The potentially important role of the nonequilibrium phonons at lasing threshold is shown and discussed in details. It is shown that the th reshold current is strongly dependent of the power dissipated in the active region in steady state. The numerical calculations for an 8.5 mu m laser i llustrate the general issues of relaxation kinetics in quantum cascade lase rs. Temperature dependence of the threshold current is obtained in a good a greement with the experiments. (C) 1999 American Institute of Physics. [S00 21-8979(99)00702-1].