Thermal modeling of terahertz quantum-cascade lasers: Comparison of optical waveguides

We compare a set of experimental lattice temperature profiles measured in a surface-emitting terahertz (THz) quantum-cascade laser (QCL) with the results of a 2-D anisotropic heat diffusion model. We evaluate the temperature dependence of the active of the cross-plane thermal conductivity (kappa(perpendicular to)) region which is known. to be strongly anisotropic due to its superlattice-like nature. Knowledge of (kappa(perpendicular to)) and its temperature dependence is crucial in order to improve the temperature performance of THz QCLs and this has been used to investigate the longitudinal lattice temperature distribution of the active region and to compare the thermal properties of metal-metal and semi-insulating surface-plasmon THz optical waveguides using a 3-D anisotropic heat diffusion model.