# Optimal pulse propagation in an inhomogeneously gas-filled hollow-core fiber

## TL;DR

This paper investigates how optical pulses propagate in a hollow-core fiber filled with inhomogeneous cold atoms, revealing how spectral distortions caused by micro-lensing can be corrected through optimal detuning.

## Contribution

It introduces an analytical two-layer model to understand pulse aberrations in inhomogeneous atomic gases within hollow-core fibers and demonstrates how to mitigate distortions via detuning.

## Key findings

- Spectral distortions are caused by micro-lensing effects.
- A two-layer model explains the aberrations.
- Optimal detuning can rectify spectral distortions.

## Abstract

We study optical pulse propagation through a hollow-core fiber filled with a radially inhomogeneous cloud of cold atoms. A co-propagating control field establishes electromagnetically induced transparency. In analogy to a graded index fiber, the pulse experiences micro-lensing and the transmission spectrum becomes distorted. Based on a two-layer model of the complex index of refraction, we can analytically understand the cause of the aberration, which is corroborated by numerical simulations for a radial Gaussian-shaped function. With these insights, we show that the spectral distortions can be rectified by choosing an optimal detuning from one-photon resonance.