Self-tuned quantum dot gain in photonic crystal lasers

TL;DR

This paper demonstrates ultra-low threshold lasing in photonic crystal lasers using only a few quantum dots, with a self-tuning mechanism enabling resonance despite initial detuning.

Contribution

It reveals that a small number of quantum dots can achieve lasing through a self-tuning process in photonic crystal nanocavities, a novel insight into quantum dot laser operation.

Findings

Lasing achieved with 1-3 quantum dots as gain medium.

Photon correlation measurements confirm transition to coherent light.

Self-tuning resonance mechanism enables lasing despite initial detuning.

Abstract

We demonstrate that very few (1 to 3) quantum dots as a gain medium are sufficient to realize a photonic crystal laser based on a high-quality nanocavity. Photon correlation measurements show a transition from a thermal to a coherent light state proving that lasing action occurs at ultra-low thresholds. Observation of lasing is unexpected since the cavity mode is in general not resonant with the discrete quantum dot states and emission at those frequencies is suppressed. In this situation, the quasi-continuous quantum dot states become crucial since they provide an energy-transfer channel into the lasing mode, effectively leading to a self-tuned resonance for the gain medium.