Multiphoton experiments using fibre pair photon sources

We have developed a source of time-correlated photon pairs based on phase matched four-wave mixing in a photonic crystal fiber designed to have a zero dispersion wavelength, lambda₀, close to 715nm. We generate parametric gain by pumping close to lambda₀ in the normal dispersion regime. By pumping with a pulsed titanium-sapphire (TI-SA) laser tuned to 708 nm we generate pair-photons at 583 nm and 900 nm visible to efficient silicon- based photon counting detectors. We can generate >100000 detected pairs per second (in a single spatial and temoral mode) with a few milli-watts of pump power. Using this source we have been able to show high visibility multi-photon interference, by mixing at a 50:50 beam-splitter, two heralded single photons generated in spatially separated micro-structured fibres. The source brightness meant we were able to measure high rates of four- photon generation and detection.