Indistinguishable photon pair generation using two independent silicon wire waveguides

We performed a Hong-Ou-Mandel interference experiment with 1.5 mu m band photon pairs generated through spontaneous four-wave mixing (SFWM) in two independent silicon wire waveguides (SWWs). To maintain the long-term stability of the coupling between the SWWs and optical fibers without a fiber alignment system, we employed fiber module SWWs installed in a rigid metallic case with fiber array interfaces. In addition, those signal photons that passed through a beam splitter (BS) were detected by high-speed single-photon detectors that used InGaAs avalanche photodiodes operated in a gated mode with a high gate frequency of 500 MHz. With these novel technologies, we successfully observed a quantum interference with a visibility of 73% without subtracting accidental coincidence counts in the fourfold coincidence measurement.