A numerical study of the spatial coherence of light in collective spontaneous emission

TL;DR

This paper numerically investigates the spatial coherence in collective spontaneous emission from dilute atomic ensembles, highlighting differences from laser coherence and identifying key parameters influencing coherence.

Contribution

It introduces a numerical analysis of collective spontaneous emission, emphasizing the role of atom number, sample size, and wavelength in spatial coherence without relying on population inversion.

Findings

Coherence arises from collective atom-light coupling, not laser-like mechanisms.

The coherence depends on the ratio N/(L/λ), where N is atom count, L is sample size, and λ is wavelength.

Subradiance and anti-phasing of dipoles are key to the observed coherence.

Abstract

We present a numerical study of the spatial coherence of light that is radiated from a dilute ensemble of atoms. The spatial coherence is established as a result of the collective (cooperative) coupling of the atoms to the light, and is qualitatively different from the coherence of a laser. Specifically, the coherence in collective spontaneous emission does not rely on population inversion and stimulated emission, is governed by anti-phasing of the dipoles (subradiance), and the key figure-of-merit for the observed coherence is N /(L/{\lambda}) . Here, N is the number of atoms in the ensemble, L is the size of the sample, and {\lambda} is the wavelength of the emitted light.