Strong and weak coupling limits in optics of quantum well excitons

TL;DR

This paper investigates the transition between strong and weak coupling regimes in quantum well exciton-photon interactions, highlighting the role of damping and providing a unified description of the phenomena with numerical analysis for GaAs wells.

Contribution

It introduces a comprehensive analysis of the strong-weak coupling transition, including the emergence of an anomalous dispersion branch and universal scaling laws for radiative corrections.

Findings

Identification of a critical damping rate for the coupling transition.

Discovery of an anomalous damping-induced dispersion branch.

Universal scaling of radiative corrections near the photon cone.

Abstract

A transition between the strong (coherent) and weak (incoherent) coupling limits of resonant interaction between quantum well (QW) excitons and bulk photons is analyzed and quantified as a function of the incoherent damping rate caused by exciton-phonon and exciton-exciton scattering. For confined QW polaritons, a second, anomalous, damping-induced dispersion branch arises and develops with increasing damping. In this case, the strong-weak coupling transition is attributed to a critical damping rate, when the intersection of the normal and damping-induced dispersion branches occurs. For the radiative states of QW excitons, i.e., for radiative QW polaritons, the transition is described as a qualitative change of the photoluminescence spectrum at grazing angles along the QW structure. Furthermore, we show that the radiative corrections to the QW exciton states with in-plane wavevector approaching the photon cone are universally scaled by an energy parameter rather than diverge. The strong-weak coupling transition rates are also proportional to the same energy parameter. The numerical evaluations are given for a GaAs single quantum well with realistic parameters.