Stimulated cooling of molecules on multiple rovibrational transitions with coherent pulse trains

TL;DR

This paper introduces a stimulated laser cooling method for diatomic molecules using ultrashort pulse trains that target multiple rovibrational transitions simultaneously, avoiding radiative branching issues and enabling larger optical forces.

Contribution

It presents a novel stimulated cooling technique employing frequency combs to cool molecules on multiple rovibrational transitions simultaneously, independent of decay rates.

Findings

Cooling can be achieved on multiple rovibrational transitions simultaneously.

Stimulated cooling forces can be orders of magnitude larger than traditional scattering forces.

The method avoids radiative branching problems in molecular Doppler cooling.

Abstract

We propose a method of stimulated laser cooling of diatomic molecules by counter-propagating $\pi$-trains of ultrashort laser pulses. The cooling cycles occur on the rovibrational transitions inside the same ground electronic manifold, thus avoiding the common problem of radiative branching in Doppler cooling of molecules. By matching the frequency comb spectrum of the pulse trains to spectrum of the R-branch rovibrational transitions we show that stimulated cooling can be carried out on several rovibrational transitions simultaneously, thereby increasing number of cooled molecules. The exerted optical force does not rely on the decay rates in a system and can be orders of magnitude larger than the typical values of scattering force obtained in conventional Doppler laser cooling schemes.