Floquet-Bloch Analysis for Distributed Feedback Quantum Cascade Lasers With a Non-Rectangular Top-Metal Grating Profile

A detailed description of a numerical model based on the Floquet-Bloch approach for designing distributed feedback quantum cascade lasers with a non-rectangular top-metal grating profile is presented. The numerical methods resulting in efficient numerical calculations and allowing for the accounting of over thirty partial waves are discussed. The practical examples show that a change in grating shape can change the coupling coefficient and surface loss by over a factor of two and should, therefore, be carefully controlled in quantum cascade laser design and fabrication.