Laser oscillation in a strongly coupled single quantum dot-nanocavity system

TL;DR

This paper reports the experimental demonstration of laser oscillation in a strongly coupled single quantum dot-nanocavity system, showing coherent quantum exchange and lasing at ultra-low power, advancing quantum photonics technology.

Contribution

The study experimentally achieves laser oscillation within the strong coupling regime of a single quantum dot and nanocavity, a feat previously considered difficult due to high quality factor requirements.

Findings

Laser oscillation occurs in the strong-coupling regime.

The device operates at ultra-low power levels.

Coherent quantum exchange is maintained during lasing.

Abstract

Strong coupling of photons and materials in semiconductor nanocavity systems has been investigated because of its potentials in quantum information processing and related applications, and has been testbeds for cavity quantum electrodynamics (QED). Interesting phenomena such as coherent exchange of a single quantum between a single quantum dot and an optical cavity, called vacuum Rabi oscillation, and highly efficient cavity QED lasers have been reported thus far. The coexistence of vacuum Rabi oscillation and laser oscillation appears to be contradictory in nature, because the fragile reversible process may not survive in laser oscillation. However, recently, it has been theoretically predicted that the strong-coupling effect could be sustained in laser oscillation in properly designed semiconductor systems. Nevertheless, the experimental realization of this phenomenon has remained difficult since the first demonstration of the strong-coupling, because an extremely high cavity quality factor and strong light-matter coupling are both required for this purpose. Here, we demonstrate the onset of laser oscillation in the strong-coupling regime in a single quantum dot (SQD)-cavity system. A high-quality semiconductor optical nanocavity and strong SQD-field coupling enabled to the onset of lasing while maintaining the fragile coherent exchange of quanta between the SQD and the cavity. In addition to the interesting physical features, this device is seen as a prototype of an ultimate solid state light source with an SQD gain, which operates at ultra-low power, with expected applications in future nanophotonic integrated systems and monolithic quantum information devices.