Spatial distribution of optically induced atomic excitation in a dense and cold atomic ensemble

TL;DR

This paper theoretically investigates how weak monochromatic light excites atoms in a dense, cold atomic cloud, analyzing spatial and Zeeman sublevel distributions, and exploring localization effects.

Contribution

It provides a detailed theoretical analysis of atomic excitation distribution and Zeeman sublevel populations in dense cold clouds, including effects of density and frequency, and compares scalar approximation results.

Findings

No signs of light localization in full vector model.

Strong localization appears under scalar approximation in certain conditions.

Atomic angular momentum orientation occurs at cloud boundaries.

Abstract

On the basis of our general theoretical results developed previously in JETP 112, 246 (2011), we calculate the spatial distribution of atoms excited in a dense and cold atomic cloud by weak monochromatic light. We also study the atomic distribution over different Zeeman sublevels of the excited state in different parts of the cloud. The dependence of this distribution of atomic excitation on the density of the atomic ensemble and the frequency of external emission is investigated. We show that in the boundary regions of the cloud the orientation and alignment of atomic angular momentum takes place. Analysis of the spatial distribution of atomic excitation shows no noticeable signs of light localization effects even in those parameter regimes where the Ioffe-Regel criterium of strong localization is satisfied. However, comparative calculations performed in the framework of the scalar approximation to the dipole-dipole interaction reveals explicit manifestation of strong localization under some conditions.