Generalized dicke model:δm=±2 transitions

Abstract

The theory of two-atom quantum transitions with frequency doubling of the emitted or absorbed photons in coherent optical processes is constructed. Third-order quantum electrodynamics (QED) effects, including virtual photon exchange and emission (absorption) of a double frequency real photon, are considered. In these effects, the two parts of the interaction accounting for intermediate states with positive or negative frequencies in the atomic spectrum are separated. Correspondingly, the electron and positron polarizations of the medium leading to the appearance of two mechanisms of frequency doubling with different physical properties are distinguished. In this paper, a generalized Dicke model for a system of N two-level atoms is used to describe coherent processes in the electric dipole approximation, allowing quantum transitions with ΔM=±1, ±2, where M is the half-difference of the resonance level populations in the atoms. In the framework of this model, a formula for the intensity of quantum transitions with ΔM=±2 is obtained.