Micro lensing induced lineshapes in a single mode cold-atom hollow-core fiber interface

TL;DR

This paper investigates how micro lensing effects in a cold-atom hollow-core fiber system alter transmission lineshapes, leading to overestimated optical depths, with modeling and Rydberg EIT studies confirming the phenomenon.

Contribution

It introduces a model linking micro lensing and mode selection to observed lineshape alterations in cold-atom fiber interfaces.

Findings

Micro lensing causes significant lineshape distortions.

Overestimation of optical depth occurs at high atom densities.

Modeling and Rydberg EIT experiments confirm the effects.

Abstract

We report on the observation of strong transmission line shape alterations in a cold-atom hollow-core fiber interface. We show that this can lead to a significant overestimation of the assigned resonant optical depth for high atom densities. By modeling light beam propagation in an inhomogeneous dispersive medium, we attribute the observations to micro lensing in the atomic ensemble in combination with the mode selection of the atom-fiber interface. The approach is confirmed by studies of Rydberg EIT line shapes.