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

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.
Comment: 11 figures, 29 pages