Bright ultra-broadband fiber-based biphoton source.

In this Letter, we report a first, to the best of our knoqledge, experimental realization of a bright ultra-broadband (180 THz) fiber-based biphoton source with widely spectrally separated signal and idler photons. Such a two-photon source is realized due to the joint use of a broadband two-loop phase-matching of interacting light waves and high optical nonlinearity of a silica-core photonic crystal fiber. The high performance of the developed fiber source identifies it as an important and useful tool for a wide range of optical quantum applications.