Fingerprints of spatial charge transfer in Quantum Cascade Lasers

TL;DR

This paper demonstrates that mid-infrared transmission spectroscopy can reveal charge transfer dynamics in quantum cascade lasers, with theoretical simulations aligning with experimental observations of spectral changes during bias variations.

Contribution

It provides the first detailed correlation between charge transfer processes and spectral signatures in quantum cascade lasers using combined experimental and theoretical approaches.

Findings

Charge transfer affects spectral features in quantum cascade lasers.

Spectroscopy reveals charge localization and delocalization during operation.

Theoretical models match experimental spectral evolution.

Abstract

We show that mid infrared transmission spectroscopy of a quantum cascade laser provides clear cut information on changes in charge location at different bias. Theoretical simulations of the evolution of the gain/absorption spectrum for the $\lambda \sim$ 7.4 $\mu$m InGaAs/AlInAs/InP quantum cascade laser have been compared with the experimental findings. Transfer of electrons between the ground states in the active region and the states in the injector goes in hand with a decrease of discrete intersubband absorption peaks and an increase of broad high-energy absorption towards the continuum delocalised states above the barriers.