Influence of multi-electronic states on few-quantum-dot nanolasers

TL;DR

This study investigates the gain mechanisms in quantum-dot nanolasers, revealing that multi-electronic states, rather than just excitons, significantly contribute to lasing, supported by experimental data and theoretical modeling.

Contribution

It provides experimental evidence and a theoretical model showing multi-electronic states dominate gain in quantum-dot nanolasers, extending understanding beyond exciton contributions.

Findings

Four excitons are coupled at low power

Lasing transition occurs at low threshold with broad emission background

Gain is primarily from multi-electronic states, not just excitons

Abstract

We present an experimental and theoretical study on the gain mechanism in a photonic-crystal-cavity nanolaser with embedded quantum dots. From time-resolved measurements at low excitation power we find that four excitons are coupled to the cavity. At high excitation power we observe a smooth low-threshold transition from spontaneous emission to lasing. Before lasing emission sets in, however, the excitons are observed to saturate, and the gain required for lasing originates rather from multi-electronic transitions, which give rise to a broad emission background. We compare the experiment to a model of quantum-dot microcavity lasers and find that the number of emitters feeding the cavity must greatly exceed four, which confirms that the gain is provided by multi-electronic states. Our results are consistent with theoretical predictions.