Radiation eigenmodes of Dicke superradiance

We calculate the field eigenmodes of the superradiant emission from an ensemble of N two-level atoms and confirm the results of other authors that Dicke superradiant emission is restricted to a small number of modes, with more than 90% of the photons emitted in a single dominant mode. While numerical techniques are effective due to the symmetry of the problem, we develop also an analytical method to approximate the modes in the limit of a large number of emitters.