ON THE KINETIC-THEORY OF THE QUANTUM CASCADE LASER

The exact solution is found of the system of coupled kinetic equations for the distribution functions of electrons and optical phonons in Qu antum Cascade Laser. It is shown that under definite conditions the pr ocesses of optical phonon accumulation and reabsorption take place. Th e threshold current can be substantially reduced in such a situation d ue to the increase of the upper subband electrons lifetime. The effect is proportional to the difference in effective masses in upper and lo wer subbands which results from the nonparabolicity of bare energy spe ctrum.