Mid-infrared quantum cascade laser waveguide losses: An anisotropic complex permittivity model

An alternative approach to the calculation of waveguide losses in quantum cascade lasers is described. It considers the active medium as an optically anisotropic material with the in-plane complex permittivity described by the bulk-like Drude model, and the perpendicular permittivity calculated from the full solution of time-dependent rate equations for the electron densities in the presence of the laser radiation. The influence of the actual lattice and electron temperature on the active medium properties (bulk mobility and perpendicular permittivity) is accounted for. The calculated losses are compared to the available experimental values.