Continuous cavity-QED with an atomic beam

TL;DR

This paper presents a continuous atomic beam coupled to an optical cavity, demonstrating collective strong coupling, normal-mode splitting, and continuous optical gain, paving the way for advanced cavity-QED phenomena like superradiant lasing.

Contribution

It introduces a novel continuous atomic beam system for cavity-QED, enabling sustained atom-light interactions and observation of collective phenomena.

Findings

Achieved a transition to collective strong coupling with normal-mode splitting.

Observed a second phase with binary normal-mode splitting due to atomic velocity offset.

Measured continuous optical gain in the collective strong coupling regime.

Abstract

Atoms coupled to cavities provide an exciting playground for the study of fundamental interactions of atoms mediated through a common channel. Many of the applications of cavity-QED and cold-atom experiments more broadly, suffer from limitations caused by the transient nature of an atomic loading cycle. The development of continuous operation schemes is necessary to push these systems to the next level of performance. Here we present a machine designed to produce a continuous flux of collimated atoms that traverse an optical cavity. The atom-light interaction is enhanced by a fast-decaying cavity optimal for studying phenomena where atomic properties dominate. We demonstrate the transition to a collective strong coupling regime heralded by a normal-mode splitting. We observe a second phase with a binary normal-mode splitting born from an offset in the mean velocity of the atoms. Inverting the atomic ensemble in the collective strong coupling regime, we measure continuous optical gain. This work sets the stage for studying threshold conditions for continuous collective phenomena, such as continuous superradiant lasing.