Cold atom confinement in an all-optical dark ring trap

TL;DR

This paper demonstrates the creation of a dark, toroidal optical trap for rubidium atoms using a spatial light modulator to generate Laguerre-Gaussian modes, achieving long atom confinement times and optimizing trap alignment.

Contribution

It introduces a novel all-optical dark ring trap for cold atoms using a spatial light modulator to shape laser modes, with detailed lifetime measurements and optimization techniques.

Findings

Achieved ~1.5 seconds atom lifetime in the trap

Demonstrated programmable trap alignment using the modulator

Compared experimental results with numerical simulations

Abstract

We demonstrate confinement of $^{85}$Rb atoms in a dark, toroidal optical trap. We use a spatial light modulator to convert a single blue-detuned Gaussian laser beam to a superposition of Laguerre-Gaussian modes that forms a ring-shaped intensity null bounded harmonically in all directions. We measure a 1/e spin-relaxation lifetime of ~1.5 seconds for a trap detuning of 4.0 nm. For smaller detunings, a time-dependent relaxation rate is observed. We use these relaxation rate measurements and imaging diagnostics to optimize trap alignment in a programmable manner with the modulator. The results are compared with numerical simulations.