# Laser-cooled caesium atoms confined with magic-wavelength dipole inside a hollow-core photonic-bandgap fiber

## TL;DR

This paper demonstrates loading laser-cooled caesium atoms into a hollow-core fiber using a magic-wavelength dipole trap, enabling long-term, continuous probing by eliminating AC-Stark shifts and inhomogeneous broadening.

## Contribution

It introduces a novel method of trapping caesium atoms in a hollow-core fiber with a magic wavelength, allowing for extended, stable atomic measurements.

## Key findings

- Achieved loading of up to 1.7 x 10^4 atoms inside the fiber.
- Extended continuous probing time to approximately 1 millisecond.
- Reduced inhomogeneous broadening and AC-Stark shifts in spectroscopy measurements.

## Abstract

We report loading of laser-cooled caesium atoms into a hollow-core photonic-bandgap fiber and confining the atoms in the fiber's 7 $\mu m$ diameter core with a magic-wavelength dipole trap at $\sim$935 nm. The use of the magic wavelength removes the AC-Stark shift of the 852nm optical transition in caesium caused by the dipole trap in the fiber core and suppresses the inhomogeneous broadening of the atomic ensemble that arises from the radial distribution of the atoms. This opens the possibility to continuously probe the atoms over time scales of a millisecond -- approximately 1000 times longer than what was reported in previous works, as dipole trap does not have to be modulated. We describe our atom loading setup and its unique features and present spectroscopy measurements of the caesium's D$_{2}$ line in the continuous wave dipole trap with up to $1.7 \times 10^{4}$ loaded inside the hollow-core fiber.