Ultralow noise miniature external cavity semiconductor laser

TLDR

Optical metrology demands lasers with high spectral purity in compact, environmentally robust packages, yet chip‑scale devices with sub‑100 Hz linewidths have not been demonstrated. The study reports the realization of a heterogeneously integrated, chip‑scale semiconductor laser with sub‑Hz instantaneous linewidth. The authors achieve this by integrating the laser with an external cavity, producing a 30‑Hz integral linewidth and sub‑Hz instantaneous linewidth.

Abstract

Abstract Advanced applications in optical metrology demand improved lasers with high spectral purity, in form factors that are small and insensitive to environmental perturbations. While laboratory-scale lasers with extraordinarily high stability and low noise have been reported, all-integrated chip-scale devices with sub-100 Hz linewidth have not been previously demonstrated. Lasers integrated with optical microresonators as external cavities have the potential for substantial reduction of noise. However, stability and spectral purity improvements of these lasers have only been validated with rack-mounted support equipment, assembled with fibre lasers to marginally improve their noise performance. In this work we report on a realization of a heterogeneously integrated, chip-scale semiconductor laser featuring 30-Hz integral linewidth as well as sub-Hz instantaneous linewidth.