Coherence properties of spontaneous parametric down-conversion pumped by a multi-mode cw diode laser

Coherence properties of the photon pair generated via spontaneous parametric down-conversion pumped by a multi-mode cw diode laser are studied with a Mach-Zehnder interferometer. Each photon of the pair enters a different input port of the interferometer and the biphoton coherence properties are studied with a two-photon detector placed at one output port. When the photon pair simultaneously enters the interferometer, periodic recurrence of the biphoton de Broglie wave packet is observed, closely resembling the coherence properties of the pump diode laser. These properties could be useful for building engineered entangled photon sources based on diode laser-pumped spontaneous parametric down-conversion.