Solid State Electrically Injected Exciton-Polariton Laser

TLDR

Inversionless ultralow‑threshold coherent emission, or polariton lasing, can be achieved by spontaneous radiative recombination from a degenerate polariton condensate with non‑resonant excitation, a regime previously accessed only with optical pumping. The authors employ modulation doping of the quantum wells to induce polariton‑electron scattering and apply a 7 T magnetic field in Faraday geometry to raise the exciton‑polariton saturation density, enabling operation at 30 K. Coherent emission is observed from a GaAs quantum‑well microcavity diode with electrical injection, revealing a macroscopic, degenerate condensate evidenced by angle‑resolved luminescence, current–light characteristics, spatial coherence, and output polarization.

Abstract

Inversionless ultralow threshold coherent emission, or polariton lasing, can be obtained by spontaneous radiative recombination from a degenerate polariton condensate with nonresonant excitation. Such excitation has, hitherto, been provided by an optical source. Coherent emission from a GaAs-based quantum well microcavity diode with electrical injection is observed here. This is achieved by a combination of modulation doping of the wells, to invoke polariton-electron scattering, and an applied magnetic field in the Faraday geometry to enhance the exciton-polariton saturation density. These measures help to overcome the relaxation bottleneck and to form a macroscopic and degenerate condensate as evidenced by angle-resolved luminescence, light-current characteristics, spatial coherence, and output polarization. The experiments were performed at 30 K with an applied field of 7 T.