THz lasing in a polariton system: Quantum theory

TL;DR

This paper presents a quantum theoretical analysis of terahertz (THz) lasing in a semiconductor microcavity system, identifying conditions for THz laser operation based on polariton interactions and cavity design.

Contribution

It introduces a quantum model for THz lasing in polariton systems and highlights the importance of cavity quality and phonon relaxation in achieving lasing.

Findings

THz lasing is feasible with a good THz cavity and proper polariton lasing conditions.

Depletion of the upper polariton mode must be minimized for lasing.

Pillar microcavities are promising candidates for THz laser realization.

Abstract

We study the laser regime of terahertz (THz) emission from a semiconductor microcavity in the strong coupling regime, where optical transitions between upper and lower exciton-polariton modes are allowed due to the mixing of the upper mode with one of the dark exciton states. Using a system of master-Boltzmann equations describing both polariton modes and the THz mode, we calculate the first and second order coherences and the spectral shape of THz emission. This analysis shows that THz lasing in microcavities is possible provided that the system is embedded in a good THz cavity, that the optical (polariton) lasing condition is fulfilled and if the depletion of the upper polariton mode due to acoustic phonon assisted relaxation processes is reduced. This latter condition is likely to be realised in pillar microcavities, which seem to be the most suitable candidates for realisation of a THz laser.