  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.
