Continuous collective strong coupling between atoms and a high finesse optical cavity

TL;DR

This paper reports the continuous loading and strong collective coupling of a large number of strontium atoms in a high finesse optical cavity, enabling potential development of ultra-narrow linewidth lasers for precision measurements.

Contribution

It introduces a method for continuous atom loading into a high finesse cavity and demonstrates sustained strong coupling with a large atomic ensemble.

Findings

Achieved continuous strong collective coupling with vacuum Rabi splitting.

Trapped up to 10^6 atoms in an intracavity lattice.

Transported atoms along the cavity axis for potential laser applications.

Abstract

We demonstrate continuous loading of strontium atoms into a high finesse ring cavity and observe continuous strong collective coupling in the form of a vacuum Rabi splitting between the atoms and the cavity on the 7.5 kHz transition $^1{\rm S}_0$ to $^3{\rm P}_1$. The atoms are loaded into the cavity from a 3D narrow linewidth molasses, thus avoiding large magnetic field gradients and associated broadening of transition frequencies. The ring cavity allows us to realize a deterministic conveyor belt to transport atoms away from the loading region where the laser cooling beams lead to broadening of the strontium clock transition. We trap up to $10^6$ atoms in an intracavity 813 nm lattice in the Lamb-Dicke regime, and transport the atoms along the cavity axis. This work opens the path to the creation of a continuous wave superradiant laser with millihertz linewidth enabling searches for new physics and the use of high-precision optical frequency references outside of low vibration laboratory environments.