Collective Emission of an ensemble of atoms or ions after coherent excitation.
Superradiance is a phenomenon of collective emission of an ensemble of excited atoms or ions. It is similar to Superfluorescence but it starts with the coherent excitation of the ensemble, usually with an optical pulse. This Coherence leads to a macroscopic dipole moment. The maximum Intensity of the emitted Light scales with the square of the number of atoms because each atom contributes a certain amount to the emission amplitude and the intensity is proportional to the square of the amplitude.