Polarisation control of optically pumped terahertz lasers

TL;DR

This paper explores how the polarization of optical pumping influences the threshold and efficiency of terahertz lasers based on exciton transitions in semiconductor quantum wells, enabling polarization-controlled laser performance.

Contribution

It demonstrates the strong dependence of two-photon absorption and THz emission efficiency on photon polarization in exciton-based lasers, providing a method to control laser thresholds and output.

Findings

Two-photon absorption probability varies with photon polarization.

Switching from linear to circular polarization changes the lasing threshold by a factor of 5.

Optimal photon polarization configurations maximize THz emission efficiency.

Abstract

Optical pumping of excited exciton states in semiconductor quantum wells is a tool for realisation of ultra-compact terahertz (THz) lasers based on stimulated optical transition between excited (2p) and ground (1s) exciton state. We show that the probability of two-photon absorption by a 2p-exciton is strongly dependent on the polarisation of both photons. Variation of the threshold power for THz lasing by a factor of 5 is predicted by switching from linear to circular pumping. We calculate the polarisation dependence of the THz emission and identify photon polarisation configurations for achieving maximum THz photon generation quantum efficiency.