Prospects for the cavity-assisted laser cooling of molecules

TL;DR

This paper explores the potential of cavity-assisted laser cooling for molecules, focusing on overcoming Raman loss challenges and identifying conditions for efficient cooling, especially for molecules like hydroxyl radicals.

Contribution

It proposes a novel approach using optical cavities and superradiant scattering to enable laser cooling of molecules without closed transitions.

Findings

High cooperativity (>1) is necessary for lossless cooling.

Superradiant scattering can facilitate intracavity self-localization.

Potential application to hydroxyl radicals from Stark deceleration.

Abstract

Cooling of molecules via free-space dissipative scattering of photons is thought not to be practicable due to the inherently large number of Raman loss channels available to molecules and the prohibitive expense of building multiple repumping laser systems. The use of an optical cavity to enhance coherent Rayleigh scattering into a decaying cavity mode has been suggested as a potential method to mitigate Raman loss, thereby enabling the laser cooling of molecules to ultracold temperatures. We discuss the possibility of cavity-assisted laser cooling particles without closed transitions, identify conditions necessary to achieve efficient cooling, and suggest solutions given experimental constraints. Specifically, it is shown that cooperativities much greater than unity are required for cooling without loss, and that this could be achieved via the superradiant scattering associated with intracavity self-localization of the molecules. Particular emphasis is given to the polar hydroxyl radical (OH), cold samples of which are readily obtained from Stark deceleration.