We review the modeling techniques for mid-infrared quantum cascade lasers based on III/V materials, clarifies or corrects ambiguity concepts such as state-dependent effective mass, the non-parabolic kinetic energy and its modeling, and the polarized waveguide confinement in the mathematical perturbation sense.
The theory is integrated into our work on making user-friendly software for modeling quantum cascade lasers. We utilize state-of-the-art open-source platforms to construct a development environment that will keep the software both scientifically correct and software engineeringly maintainable.
Experimentally we present a new 16μm GaAs/AlGaAs quantum cascade laser design with bound-to-bound transition and strongly coupled upper and injection states. For the waveguide, we propose to utilize layers of high Al concentration for the cladding layer, which strongly reduces the waveguide loss compared to previous attempts with high-doped GaAs.
The new design is shown to have a threshold current density smaller than the record GaAs/AlGaAs based long-wavelength infrared quantum cascade lasers --- an improvement by 50% --- and the spectrum matches exactly the designed wavelength