What is measured in a photoluminescence experiment on Quantum dots embedded in a large Purcell factor microcavity?

TL;DR

This paper reveals that in photoluminescence experiments on quantum dots in high Purcell microcavities, the measured linewidth varies with excitation power, affecting the interpretation of cavity quality factors.

Contribution

It demonstrates that the observed mode linewidth in such experiments is power-dependent and provides guidelines for accurately measuring the true cavity quality factor.

Findings

Measured linewidth depends on excitation power

Spectral signatures vary with collection setup

Guidelines for correct quality factor measurement

Abstract

It is usually assumed that when performing a photoluminescence experiment on a microcavity containing an inhomogeneously broadened quantum dots ensemble, the cavity mode appears as a positive peak with a linewidth that reflects the mode quality factor Q. We show in this article that this conclusion is in general not true, and that the measured mode linewidth depends strongly on the excitation power for microcavities having large Purcell factors. We analyze theoretically this effect in the case of the micropillar cavity and we show that the same microcavity can give rise to a large variety of photoluminescence spectral signatures depending on the excitation power and collection set-up. We finally give guidelines to measure the real cavity quality factor by photoluminescence.