Modeling of Microstrip Quantum Cascade Lasers

Quantum cascade lasers are semiconductor lasers employing a quantum-engineered active region, often combined with a microstrip waveguide for optical confinement. These devices enable the efficient and compact generation of mid-infrared and terahertz radiation, as desirable for numerous applications in, e.g., metrology and sensing. In this context, often the generation of broadband frequency combs or ultrashort pulses is required. For a numerically efficient theoretical investigation of the associated laser dynamics, one-dimensional Maxwell-Bloch-type equations in the rotating-wave approximation are widely used, where the waveguide properties are represented in the optical propagation equation by effective parameters. For realistic device modeling, group velocity dispersion must be considered in addition to the effective refractive index, waveguide loss and group velocity. We introduce a stable and efficient numerical scheme for the inclusion of this effect, and show exemplary simulation results. The presented numerical approach is also relevant for optoelectronic device simulations beyond QCLs.