Broadening effects due to alloy scattering in Quantum Cascade Lasers

TL;DR

This paper investigates how alloy scattering causes broadening in Quantum Cascade Lasers, analyzing Landau level widths, optical absorption, and relaxation dynamics with numerical and theoretical methods.

Contribution

It introduces detailed calculations of alloy scattering effects on Landau levels and optical properties in QCLs, comparing numerical results with self-consistent Born approximation.

Findings

Alloy scattering broadens Landau levels significantly.

Disorder-activated forbidden transitions become prominent near level crossings.

Population relaxation at resonance occurs within subpicoseconds.

Abstract

We report on calculations of broadening effects in QCL due to alloy scattering. The output of numerical calculations of alloy broadened Landau levels compare favorably with calculations performed at the self-consistent Born approximation. Results for Landau level width and optical absorption are presented. A disorder activated forbidden transition becomes significant in the vicinity of crossings of Landau levels which belong to different subbands. A study of the time dependent survival probability in the lowest Landau level of the excited subband is performed. It is shown that at resonance the population relaxation occurs in a subpicosecond scale.