Quantum statistical theory of optical phenomena.

The purpose of this paper is to develop a density matrix formulation for optical phenomena that can be applied to both steady and transient states and to both resonance and off-resonance regions. To demonstrate the application, this theory has been applied to the steady-state one-photon and two-photon processes. We have found that, in the resonance region, the conventional equation used is incomplete; other terms that are comparable in importance have been ignored.