We present an efficient method for the calculation of the transmission characteristic of quantum cascade lasers (QCLs). A fully Schrodinger-Poisson-rate equation iteration with strained term is presented in our calculation. The two-band strained term of the Schrodinger equation is derived from the eight-band Hamiltonian. The equivalent strain energy that affects the effective mass and raises the energy level is introduced to include the biaxial strain into the conduction band profile. We simplified the model of the electron-electron scattering process and improved the calculation efficiency by about two orders of magnitude. The thermobackfilling effect is optimized by replacing the lattice temperature with the electron temperature. The quasi-subband-Fermi level is used to calculate the electron density of laser subbands. Compared with the experiment results, our method gives reasonable threshold current (depends on the assumption of waveguide loss and scattering processes) and more accurate wavelength, making the method efficient and practical for QCL simulations.

QCLs; strained Hamiltonian; electron-electron scattering; QCL characteristics

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