# Photon scattering from a cold, Gaussian atom cloud

## TL;DR

This paper investigates how polarization distribution in cold atomic clouds affects photon scattering lineshapes across different density regimes, highlighting when mean-field models suffice and when full models are necessary.

## Contribution

It identifies three polarization regimes in atomic clouds and delineates the applicability of mean-field versus full dipole models for photon scattering.

## Key findings

- Dilute clouds exhibit constant polarization magnitude.
- Denser clouds show polarization buildup at the front for near-resonant light.
- Very dense clouds require full dipole models due to atom-atom correlations.

## Abstract

We study the effect of a weakly driven atomic cloud's polarization distribution on its photon scattering lineshape. In doing this, we find three distinct polarization regimes. First, for dilute clouds, the polarization magnitude is relatively constant. Second, for denser clouds, polarization builds at the front of the cloud for near-resonant light. Third, when the cloud condenses to the point where its dimensions become comparable to the wavelength, light refocuses towards the back of the cloud for red detuning. For these regimes, we show which `mean-field' frameworks accurately describe the differing photon scattering lineshapes. Finally, for even denser clouds, mean field models become inaccurate and necessitate the full point dipole model that includes atom-atom correlations.