Efficient Three-Dimensional Electromagnetic Modeling of Metal–Metal Waveguides Employed for Quantum Cascade Lasers Operating in the THz Band

This paper presents a novel computationally-efficient full-wave fully-numerical approach to the electromagnetic modeling of quantum cascade laser (QCL) structures based on metal-clad dielectric waveguides with the aid of a three-dimensional electromagnetic solver with no need (in practical cases) for separate analyses of propagation within the waveguide. The described method enables to calculate the resonant frequencies of an electrically long Fabry-Pérot cavity and to link them to particular propagating (transverse) modes of the waveguide. It also allows to easily analyze the origin of losses in the structure including the volumetric losses within the dielectric ridge as well as the nonideal and frequency dependent behavior of mirrors and/or antennas that terminate the waveguide for an improved coupling to the free space. Some examples of such structures are given and their performance in the context of QCLs is evaluated using the proposed method.