Sub-Doppler laser cooling of 40K with Raman gray molasses on the D2 line

TL;DR

This paper demonstrates effective sub-Doppler laser cooling of 40K atoms using Raman gray molasses on the D2 line with red-detuned lasers, achieving low temperatures and high atom loading efficiency.

Contribution

It introduces a novel implementation of gray molasses cooling on the D2 line of 40K with red detuning, supported by theoretical modeling and simulations.

Findings

Achieved temperatures of 48 microKelvin.

Loaded over 9 million atoms into an optical dipole trap.

Supported experimental results with optical Bloch equation simulations.

Abstract

Gray molasses is a powerful tool for sub-Doppler laser cooling of atoms to low temperatures. For alkaline atoms, this technique is commonly implemented with cooling lasers which are blue-detuned from either the D1 or D2 line. Here we show that efficient gray molasses can be implemented on the D2 line of 40K with red-detuned lasers. We obtained temperatures of 48(2) microKelvin, which enables direct loading of 9.2(3)*10^6 atoms from a magneto-optical trap into an optical dipole trap. We support our findings by a one-dimensional model and three-dimensional numerical simulations of the optical Bloch equations which qualitatively reproduce the experimentally observed cooling effects.