Ultra-bright narrow-band down-conversion source for atom-photon interaction

There has been increasing interest in the generation of such photon pairs using a spontaneous parametric down-conversion (SPDC) source inside an optical cavity to enhance the down-conversion into modes resonant to the cavity, each of the modes having a MHz spectrum. These optical parametric oscillators (OPO) operated far below threshold also provide a well defined spatial mode. Our setup consists of a bow-tie cavity with a periodically poled KTP crystal as nonlinear medium, phase-matched for parametric down-conversion. This photon-pair source is designed to provide photons suitable for interaction with atoms. These photons could be directly used in applications towards a quantum memory of light, like in experiments on slow light or the storage of single photons in EIT media. In this way an optical polarization rotation in an atomic sample could be measured achieving super-resolution.