Confinement of ultracold atoms in a Laguerre-Gaussian laser beam created with diffractive optics

TL;DR

This paper demonstrates the confinement of ultracold rubidium atoms using a Laguerre-Gaussian laser beam, with the confinement geometry controlled by the laser's detuning, enabling low-shift trapping in different configurations.

Contribution

It introduces a method for 2D confinement of ultracold atoms in a Laguerre-Gaussian beam with tunable geometry based on detuning, including modeling of mode imperfections.

Findings

Atoms confined to the dark central node with blue detuning.

Atoms confined to the outer ring with red detuning.

Mode misalignments cause azimuthal intensity variations.

Abstract

We report 2D confinement of Rb 87 atoms in a Laguerre-Gaussian laser beam. Changing of the sign of the detuning from the atomic resonance dramatically alters the geometry of the confinement. With the laser detuned to the blue, the atoms are confined to the dark, central node of the Laguerre-Gaussian laser mode. This trapping method leads to low ac Stark shifts to the atomic levels. Alternatively, by detuning the laser to the red of the resonance, we confine atoms to the high intensity outer ring in a multiply-connected, toroidal configuration. We model the confined atoms to determine azimuthal intensity variations of the trapping laser, caused by slight misalignments of the Laguerre-Gaussian mode generating optics.