Cavity field spectra of the two-atom two-photon Jaynes-Cummings model

The cavity field spectra for a pair of coupled two-level atoms with single mode of the radiation in an ideal cavity via two-photon resonant transition processes are investigated. The results for the initial fields in pure number state, coherent state or squeezed vacuum state are presented and discussed. The effects of dipole-dipole interaction of atoms and exchange symmetry of the initial state of atoms on the cavity field spectra are analyzed. It is found that the odd peaks structure of the cavity field spectra appears for various initial fields except vacuum state with the two atoms in the excited states. This is in contrast with the even peaks of the emission spectra of the Sham model. When only one of the two atoms is in the excited state, the exchange symmetry of the atoms plays a decisive role in the structure of the cavity field spectra.