Sagnac-type entangled photon source using only conventional polarization optics

Abstract

We designed and implemented a novel combination of a Sagnacinterferometer with a Mach-Zehnder interferometer for a source of polarizationentangled photons. The new versatile configuration does not require multi-wavelength polarization optics, yet it performs with a good polarization quality and phase-stability over a wide wavelength range. We demonstrate the interferometer using only standard commercial optics to experimentally realize the pulsed generation of polarizationentangled photon-pairs at wavelengths of 764 nm and 1221 nm via type-I spontaneous four-wave mixing in a polarization-maintaining fiber. Polarization entanglement was verified by a polarization-correlation measurement with a visibility of 95.5 % from raw coincidence counts and the violation of the Clauser-Horne-Shimony-Holt (CHSH) inequality with S = 2.70 ± 0.04. The long-term phase-stability was characterized by an Allan deviation of 8 • over an integration time of about 1 hour with no active phase-stabilization.