Role of pump coherence in two-photon interferometry
Junlin Liang, S. M. Hendrickson, T. B. Pittman · Physical Review A · 2011
We use a parametric down-conversion source pumped by a short-coherence-length continuous-wave (CW) diode laser to perform two-photon interferometry in an intermediate regime between the more familiar Franson-type experiments with a long-coherence-length pump laser, and the short pulsed pump ``time-bin'' experiments pioneered by Gisin's group. The use of a time-bin-like Mach-Zehnder interferometer in the CW pumping beam induces coherence between certain two-photon amplitudes, while the CW nature of the experiment prevents the elimination of remaining incoherent ones. The experimental results highlight the role of pump coherence in two-photon interferometry.