Optical phonon scattering and theory of magneto-polarons in a quantum cascade laser in a strong magnetic field

TL;DR

This paper presents a theoretical analysis of carrier relaxation mechanisms in a quantum cascade laser under strong magnetic fields, focusing on alloy disorder and electron-phonon interactions, predicting nonexponential decay of electron populations.

Contribution

It introduces a magneto-polaron formalism to study electron relaxation in QCLs considering both alloy disorder and strong electron-phonon coupling, a novel approach for this context.

Findings

Fast non-radiative relaxation via LO phonon scattering in weak coupling regime.

Nonexponential decay of upper level electron populations in strong coupling regime.

Effect of alloy disorder on electron relaxation dynamics.

Abstract

We report a theoretical study of the carrier relaxation in a quantum cascade laser (QCL) subjected to a strong magnetic field. Both the alloy (GaInAs) disorder effects and the Frohlich interaction are taken into account when the electron energy differences are tuned to the longitudinal optical (LO) phonon energy. In the weak electron-phonon coupling regime, a Fermi's golden rule computation of LO phonon scattering rates shows a very fast non-radiative relaxation channel for the alloy broadened Landau levels (LL's). In the strong electron-phonon coupling regime, we use a magneto-polaron formalism and compute the electron survival probabilities in the upper LL's with including increasing numbers of LO phonon modes for a large number of alloy disorder configurations. Our results predict a nonexponential decay of the upper level population once electrons are injected in this state.