Continuous momentum state lasing and cavity frequency-pinning with laser-cooled strontium atoms

TL;DR

This paper demonstrates hours-long continuous lasing with laser-cooled strontium atoms in a ring cavity, revealing new mechanisms for stable lasing and frequency stabilization relevant for quantum sensing and simulation.

Contribution

It reports the first observation of truly continuous lasing from laser-cooled atoms, with a novel atomic momentum inversion mechanism and suppressed frequency sensitivity.

Findings

Hours-long continuous lasing achieved with laser-cooled atoms

Atomic momentum inversion enables continuous lasing

Cavity frequency sensitivity is suppressed 120-fold

Abstract

Laser-cooled gases of atoms interacting with the field of an optical cavity are a powerful tool for quantum sensing and the simulation of open and closed quantum systems. They can display spontaneous self-organisation phase transitions, time crystals, new lasing mechanisms, squeezed states for quantum sensing, protection of quantum coherence, and dynamical phase transitions. However, all of these phenomena are explored in a discontinuous manner due to the need to stop and reload a new ensemble of atoms. Here we report the observation of hours-long continuous lasing from laser-cooled $^{88}$Sr atoms continuously loaded into a ring cavity. The required inversion to produce lasing arises from inversion in the atomic momentum degree of freedom, a mechanism related directly to self-organization phase transitions and collective atomic recoil lasing, both of which were previously only observed in a cyclic fashion compared to the truly continuous behavior here. Further, the sensitivity of the lasing frequency to cavity frequency changes is 120 fold suppressed due to an atomic loss mechanism, opening an interesting new path to compensate cavity frequency noise for realizing narrow frequency references. This work opens the way for continuous cavity QED quantum simulation experiments as well as continuous superradiant lasers.