Sub-Doppler laser cooling of potassium atoms

TL;DR

This paper demonstrates that combining dark optical molasses with adiabatic laser parameter ramping enables sub-Doppler cooling of bosonic potassium isotopes, achieving temperatures significantly below the Doppler limit.

Contribution

It introduces a novel cooling scheme for potassium atoms that overcomes previous limitations caused by small hyperfine splitting.

Findings

Achieved temperatures as low as 25 microKelvin for 39K

Achieved temperatures as low as 47 microKelvin for 41K

Demonstrated effectiveness in high-density atomic samples

Abstract

We investigate sub-Doppler laser cooling of bosonic potassium isotopes, whose small hyperfine splitting has so far prevented cooling below the Doppler temperature. We find instead that the combination of a dark optical molasses scheme that naturally arises in this kind of systems and an adiabatic ramping of the laser parameters allows to reach sub-Doppler temperatures for small laser detunings. We demonstrate temperatures as low as 25(3)microK and 47(5)microK in high-density samples of the two isotopes 39K and 41K, respectively. Our findings will find application to other atomic systems.