Pulsed sagnac source of polarisation entangled photon pairs

In this paper, the authors describe a pulsed polarisation-entangled photon pair source based on a Sagnac interferometer loop. A 76 MHz repetition rate Ti:sapphire creates 2 ps light pulses at a wavelength of 808 nm. This light is frequency doubled in a BIBO crystal to produce 404 nm pulses. Spontaneous parametric downconversion is realised using a type II periodically poled KTP crystal. Finally, the downconverted photon pairs are coupled into single mode fiber.