Transmitted and fluorescent spectra of a two-level atom in an optical parametric oscillator

Summary form only given. The interaction of a single two-level atom with the electromagnetic field inside an optical parametric oscillator (OPO) gives rise to interesting and complex features in the fluorescent spectrum and transmitted spectra. In the weak driving-field limit the system can be thought of as one atom and an optical cavity driven by an occasional pair of correlated photons. Equivalently, these correlated pairs of photons can be viewed as a source of weakly squeezed light incident on an atom in a cavity. It is in this limit that we treat the problem, and find for one parameter regime sub-natural linewidth spectral features which persist although the system interacts with only one pair of photons at a time (i.e. the squeezing parameter N tends toward zero). Our technique is based on one successfully applied to other atom-cavity problems. We begin with a Hamiltonian describing the effective two-photon driving field (generated by the OPO itself), along with the two-level atom, the cavity field and their mutual coupling strengths.