Controlling many-body effects in the midinfrared gain and THz absorption of quantum cascade laser structures

TL;DR

This paper develops a microscopic quantum mechanical theory to analyze how many-body Coulomb interactions influence gain and absorption in quantum cascade laser structures, highlighting control via bias adjustments.

Contribution

It introduces a nonequilibrium Green function approach to quantify Coulomb effects on optical properties in quantum cascade lasers, emphasizing the role of wavefunction overlap and bias.

Findings

Coulomb interactions significantly affect gain and absorption depending on wavefunction overlap.

Bias voltage can modulate the strength of many-body effects.

The theory provides insights into optimizing quantum cascade laser performance.

Abstract

A many-body theory based on nonequilibrium Green functions, in which transport and optics are treated on a microscopic quantum mechanical basis, is used to compute gain and absorption in the optical and THz regimes in quantum cascade laser structures. The relative importance of Coulomb interactions for different intersubband transitions depends strongly on the spatial overlap of the wavefunctions and the specific nonequilibrium populations within the subbands. The magnitude of the Coulomb effects can be controlled by changing the operation bias.