Cold atom guidance in a capillary using blue-detuned, hollow optical modes

Joseph A Pechkis,Fredrik K Fatemi

doi:10.1364/oe.20.013409

Abstract

We demonstrate guiding of cold 85Rb atoms through a 100-micron-diameter hollow core dielectric waveguide using cylindrical hollow modes. We have transported atoms using blue-detuned light in the 1st order, azimuthally-polarized TE01 hollow mode, and the 2nd order hollow modes (HE31, EH11, and HE12), and compared these results with guidance in the red-detuned, fundamental HE11 mode. The blue-detuned hollow modes confine atoms to low intensity along the capillary axis, far from the walls. We determine scattering rates in the guides by directly measuring the effect of recoil on the atoms. We observe higher atom numbers guided using red-detuned light in the HE11 mode, but a 10-fold reduction in scattering rate using the 2nd order modes, which have an r4 radial intensity profile to lowest order. We show that the red-detuned guides can be used to load atoms into the blue-detuned modes when both high atom number and low perturbation are desired.

Highlights

Atom guides using hollow optical fibers (HOFs) have continued to be of interest for potential use in nonlinear optics and optical switches [1,2], atom transport [3], and atom interferometry [4]
Atoms have been guided in photonic crystal fibers (PCF) [1,2] in which the small mode-field area leads to strong atom-photon coupling and large optical depths
For sufficiently high scattering rates that occur at very small, the atoms cannot propagate through the capillary, either because they scatter enough photons to boil out of the guide beam potential, or because photon pressure from off-resonant scattering overcomes gravity. This pressure can be useful for manipulating atom velocities inside optical guides: Atom levitation due to guide radiation pressure was observed at very small detunings in Ref. [13], and additional near-resonant beams have been suggested for controlling atom motion inside PCF [2]

Summary

Introduction

Atom guides using hollow optical fibers (HOFs) have continued to be of interest for potential use in nonlinear optics and optical switches [1,2], atom transport [3], and atom interferometry [4]. Guiding is enabled through the optical dipole potential: The force on an atom exposed to an off-resonant, spatially-varying intensity distribution is attractive (repulsive) when the laser is tuned below (above) the atomic resonance. This has led to numerous optical guiding schemes tailored for particular applications [1, 4,5,6,7,8,9,10]. While we observe the highest atom number guidance using red-detuned light, we show that the blue-detuned beams guide atoms with a 10-fold reduction in the recoil scattering rate and that the blue-detuned guides can be loaded from a red-detuned beam inside the capillary for dark confinement with high atom flux, which may be useful for extending measurement time windows for tightly confined atoms [1]

Experimental setup

Experiments

Guiding as a function of detuning

Photon scattering rates

Conclusions