Electrically-injected room-temperature waveguide polariton laser

TL;DR

This paper reports the first electrically-pumped room-temperature waveguide polariton laser using GaN, demonstrating key features like operation without population inversion and potential for integrated devices.

Contribution

It introduces an electrically-driven exciton-polariton laser at room temperature with a GaN-based architecture, enabling practical polariton devices.

Findings

Operates at room temperature in a mode-locked regime.

Breaks the transparency condition, functioning with only 20% cavity injection.

Achieves polariton lasing with a short 60μm cavity length.

Abstract

Exciton-polariton lasers are coherent light sources which do not require the population inversion (transparency) condition to be fulfilled. They have been conceptualized at the end of the XXth century but until now they operate almost exclusively under optical injection, which severely limits the widespread integration of the polariton-based devices implemented so far. Here we tackle this issue by reporting an electrically-pumped exciton-polariton laser based on GaN and operating at room temperature in a mode-locked regime. The laser architecture is close to the geometry of commercial ridge-waveguide GaN lasers, but based on a bulk GaN active region instead of quantum wells. Unique features of polariton lasers are demonstrated, in particular the breakdown of the transparency condition, which enables our polariton lasers to operate even when only a small fraction (20\%) of the cavity length is injected. Moreover, the large polaritonic gain allows for the operation of a short cavity length (60$\mu m$) compared to commercial lasers. From the very same sample, we also achieve polariton lasing under optical injection, confirming that the doped layers necessary for electrical injection do not prevent strong-coupling nor polariton lasing. Our results open a new perspective for polariton-based devices.