Three Dimensional Raman Cooling using Velocity Selective Rapid Adiabatic Passage

TL;DR

This paper introduces a novel 3D Raman cooling technique using velocity selective rapid adiabatic passage with chirped pulses, achieving near-unity transfer efficiency and significant temperature reduction in trapped cesium atoms.

Contribution

The authors develop and demonstrate a new Raman cooling method employing frequency-chirped pulses for efficient, large-scale velocity class addressing in 3D cooling of trapped atoms.

Findings

Cooling cesium atoms to 2 μK in 100 ms

Achieved atomic density of 1.3×10^{12} at/cm^3

Phase-space density increased by a factor of 20

Abstract

We present a new and efficient implementation of Raman cooling of trapped atoms. It uses Raman pulses with an appropriate frequency chirp to realize a velocity selective excitation through a rapid adiabatic passage. This method allows to address in a single pulse a large number of non zero atomic velocity classes and it produces a nearly unity transfer efficiency. We demonstrate this cooling method using cesium atoms in a far-detuned crossed dipole trap. Three-dimensional cooling of $1 \times 10^{5}$ atoms down to $2 \mu$K is performed in 100 ms. In this preliminary experiment the final atomic density is $1.3\times 10^{12}$ at/cm$^3$ (within a factor of 2) and the phase-space density increase over the uncooled sample is 20. Numerical simulations indicate that temperatures below the single photon recoil temperature should be achievable with this method.