Light propagation beyond the mean-field theory of standard optics

TL;DR

This paper compares traditional optics with numerical simulations for light propagation in dense atomic gases, revealing failures of standard optics at high densities due to atom correlations from dipole interactions.

Contribution

It demonstrates the limitations of mean-field optics in dense gases and highlights the importance of atom correlations in light propagation.

Findings

Standard optics fails at low densities.

Failure becomes significant when interatomic separation approaches the wavelength.

Correlations from dipole interactions cause deviations from traditional models.

Abstract

With ready access to massive computer clusters we may now study light propagation in a dense cold atomic gas by means of basically exact numerical simulations. We report on a direct comparison between traditional optics, that is, electrodynamics of a polarizable medium, and numerical simulations in an elementary problem of light propagating through a slab of matter. The standard optics fails already at quite low atom densities, and the failure becomes dramatic when the average interatomic separation is reduced to around $k^{-1}$, where $k$ is the wave number of resonant light. The difference between the two solutions originates from correlations between the atoms induced by light-mediated dipole-dipole interactions.