Laser-driven Sisyphus cooling in an optical dipole trap

TL;DR

This paper introduces a new laser cooling method called Sisyphus cooling in an optical dipole trap, which efficiently cools atoms like strontium and ytterbium by exploiting differential AC Stark shifts, potentially reaching quantum degeneracy rapidly.

Contribution

The paper proposes a novel Sisyphus cooling scheme utilizing trap-induced AC Stark shifts, effective for alkaline-earth-like atoms with narrow electronic transitions, demonstrated through numerical simulations.

Findings

Achieves recoil and Doppler temperature limits in simulations

Requires few scattered photons for effective cooling

Potentially reaches quantum degeneracy in sub-second timescales

Abstract

We propose a novel Sisyphus cooling scheme for atoms confined in a far off resonance optical dipole trap. Utilizing the differential trap-induced AC Stark shift, two electronic levels of the atom are resonantly coupled by a cooling laser preferentially near the trap bottom. After absorption of a cooling photon, the atom loses energy by climbing the steeper potential, and then spontaneously decays preferentially away from the trap bottom. The proposed method is particularly suited to cooling alkaline-earth-like atoms where two-level systems with narrow electronic transitions are present. Numerical simulations for the cases of $^{88}$Sr and $^{174}$Yb demonstrate the expected recoil and Doppler temperature limits. The method requires a relatively small number of scattered photons and can potentially lead to phase space densities approaching quantum degeneracy in sub-second timescales.