Time-bin entangled photon pairs from spontaneous parametric down-conversion pumped by a cw multi-mode diode laser

Abstract

The Franson interferometer consists of two spatially separated unbalanced Mach-Zehnder interferometers through which the signal and the idler photons from spontaneous parametric down-conversion (SPDC) are made to transmit. It is often used to prepare time-bin entanglement of two photons in the two SPDC pumping, regimes: the narrowband regime and the double-pulse regime. In the narrowband regime, the SPDC- process is pumped by a narrowband cw laser with the coherence length much longer than the path length difference of the Franson interferometer. In the double-pulse regime, the longitudinal separation between the pulse pair is made equal to the path length difference of the Franscon interferometer. In this propose another regime by which the generation of time-bin entanglement is possible and demonstrate the scheme experimentally.