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.
@article{arxiv.1012.4434,
title = {The role of pump coherence in two-photon interferometry},
author = {J. Liang and S. M. Hendrickson and T. B. Pittman},
journal= {arXiv preprint arXiv:1012.4434},
year = {2015}
}