Elementary processes of stimulated emission

We consider the simplest process of stimulated emission, i.e., evolution of an excited two-level atom interacting with a quantized electromagnetic field being initially in a one-photon state under different boundary conditions imposed on the field. We study the kinetics of evolution, spectral properties and modal composition of the radiation field emerging in such processes. It is shown that in the general case this field is only partly composed of doubly occupied modes.