Directional bistability and nonreciprocal lasing with cold atoms in a ring cavity

TL;DR

This paper demonstrates a laser using cold atoms in a ring cavity that exhibits directional bistability and tunable nonreciprocity, with potential applications in optical control and quantum technologies.

Contribution

It introduces a novel cold-atom-based laser system with controllable nonreciprocal emission and bistability, advancing understanding of light-matter interactions in ring cavities.

Findings

Laser operates in counter-propagating modes with cold atoms as gain medium

Exhibits directional bistability, switching between modes

Shows tunable nonreciprocity with atomic displacement

Abstract

We demonstrate lasing into counter-propagating modes of a ring cavity using a gas of cold atoms as a gain medium. The laser operates under the usual conditions of magneto-optical trapping with no additional fields. We characterize the threshold behavior of the laser and measure the second-order optical coherence. The laser emission exhibits directional bistability, switching randomly between clockwise and counter-clockwise modes, and a tuneable nonreciprocity is observed as the atoms are displaced along the cavity axis.