Observation of the transition from lasing driven by a bosonic to a fermionic reservoir in a GaAs quantum well microcavity

TL;DR

This study distinguishes between polariton and photon lasing in a GaAs quantum well microcavity by monitoring carrier densities and identifying two thresholds, revealing the transition from bosonic to fermionic reservoir-driven lasing.

Contribution

It demonstrates a method to differentiate polariton and photon lasing through photocurrent measurements and threshold analysis in a GaAs microcavity.

Findings

Identification of two lasing thresholds corresponding to polariton and photon lasing.

Distinct photocurrent behavior at each lasing threshold.

Evidence of a transition from bosonic to fermionic reservoir-driven lasing.

Abstract

We show that, by monitoring the free carrier reservoir in a GaAs-based quantum well microcavity under nonresonant pulsed optical pumping, lasing supported by a fermionic reservoir (photon lasing) can be distinguished from lasing supported by a reservoir of bosons (polariton lasing). Carrier densities are probed by measuring the photocurrent between lateral contacts deposited directly on the quantum wells of a microcavity that are partially exposed by wet chemical etching. We identify two clear thresholds in the input-output characteristic of the photoluminescence signal which can be attributed to polariton and photon lasing, respectively. The power dependence of the probed photocurrent shows a distinct kink at the threshold power for photon lasing due to an increased radiative recombination of free carriers as stimulated emission into the cavity mode sets in. At the polariton lasing threshold, on the other hand, the nonlinear increase of the luminescence is caused by stimulated scattering of exciton polaritons to the ground state which do not contribute directly to the photocurrent.