Dynamics of the Energy Relaxation in a Parabolic Quantum Well Laser

TL;DR

This study investigates the relaxation dynamics of parabolic quantum well lasers, demonstrating their potential for terahertz radiation production through cascade relaxation, with experimental and theoretical analysis of different microcavity configurations.

Contribution

It provides the first detailed comparison of relaxation dynamics in PQW and conventional QW microcavities, and adapts Boltzmann equations to model excitonic population evolution.

Findings

Strong difference in relaxation characteristics between PQW and QW microcavities.

Confirmation of cascade relaxation in PQW, indicating potential for terahertz emission.

Experimental and theoretical analysis aligning to support cascade relaxation mechanism.

Abstract

We explore two parabolic quantum well (PQW) samples, with and without Bragg mirrors, in order to optimise the building blocks of a Bosonic Cascade Laser. The photoluminescence spectra of a PQW microcavity sample is compared against that of a conventional microcavity with embedded quantum wells (QWs) to demonstrate that the weak coupling lasing in a PQW sample can be achieved. The relaxation dynamics in a conventional QW microcavity and in the PQW microcavity was studied by a non-resonant pump-pump excitation method. Strong difference in the relaxation characteristics between the two samples was found. The semi-classical Boltzmann equations were adapted to reproduce the evolution of excitonic populations within the PQW as a function of the pump power and the output intensity evolution as a function of the pump-pump pulse delay. Fitting the PQW data confirms the anticipated cascade relaxation, paving the way for such a system to produce terahertz radiation.