Narrow-linewidth exciton-polariton laser

TL;DR

This paper presents a high-resolution spectroscopic study of an exciton-polariton laser, revealing an ultra-narrow linewidth and long coherence time, demonstrating the potential for quantum and classical computing applications.

Contribution

It provides the first detailed experimental analysis of spectral purity and linewidth in a single-mode exciton-polariton laser, highlighting the effects of condensate confinement and pump power.

Findings

Achieved an ultra-narrow linewidth of 56 MHz.

Demonstrated a coherence time of 5.7 ns.

Showed that the excitonic reservoir does not significantly affect linewidth when condensate is well trapped.

Abstract

Exciton-polariton laser is a promising source of coherent light for low-energy applications due to its low-threshold operation. However, a detailed experimental study of its spectral purity, which directly affects its coherence properties is still missing. Here}, we present a high-resolution spectroscopic investigation of the energy and linewidth of an exciton-polariton laser in the single-mode regime, which derives its coherent emission from an optically pumped and confined exciton-polariton condensate. We report an ultra-narrow linewidth of 56~MHz or 0.24~$\mu$eV, corresponding to a coherence time of 5.7~ns. The narrow linewidth is consistently achieved by using an exciton-polariton condensate with a high photonic content confined in an optically induced trap. Contrary to previous studies, we show that the excitonic reservoir created by the pump and responsible for creating the trap does not strongly affect the emission linewidth as long as the condensate is trapped and the pump power is well above the condensation (lasing) threshold. \red{The long coherence time of the exciton-polariton system uncovered here opens up opportunities for manipulating its macroscopic quantum state, which is essential for applications in classical and quantum computing.