  We characterize a source of photon pairs based on cascade decay in a cold
Rb-87 ensemble. This source is particularly suited to generate of photons for
interaction with Rb-87 based atomic systems. We experimentally investigate the
dependence of pair generation rate, single photon heralding efficiency, and
bandwidth as a function of the number of atoms, detuning and intensity of the
pump beams. The observed power and detuning behaviors can be explained by the
steady state solution of an established three-level model of an atom.
Measurements presented here provide a useful insight on the optimization of
this kind of photon pair sources.
