Coherent Spontaneous Emission

Coherent spontaneous emission from a system of $N$ two-level atoms interacting with a quantized radiation field is treated for the case in which Dicke's "cooperation number" $r$ is macroscopically large. It is shown how to modify the quasiclassical approach to this problem to incorporate quantum effects that are lost in the self-consistent-field approximation. The statistics of the emitted radiation are found to vary markedly with the initial state of the system of atoms. The photon statistics tend to that typical of blackbody radiation when the initial state of the atomic system is that which would result from incoherent pumping ($m\sim r$). When, on the other hand, the atoms are initially in a superradiant state ($m\ll r$), the emitted radiation may be represented approximately by a coherent state.