Fully-guided polarization-correlated photon pairs at 1560 nm from a type-II SPDC-based source.

The study, reliable generation, and application of spectral and polarization-correlated biphotons is a widely researched area in the field of quantum technology. In this Letter, we report a bright narrowband source of spectral and polarization-correlated orthogonal photon-pairs around the telecom wavelength of 1560 nm from a fiber-pigtailed, type-II quasi-phase-matched, MgO-doped periodically poled lithium niobate (MgO:ppLN) ridge waveguide. We achieved a high spectral brightness of ∼5×10 photon pairs/s/mW/nm with a coincidence-to-accidental ratio (CAR) value of ∼427 and an emission bandwidth of ∼2.4 nm. Owing to its compact and narrowband nature, this source can reliably be used in commercial quantum communication systems for long-distance transmissions. The generation of such high rates of correlated orthogonal twin photons from a fully guided type-II SPDC-based source has not been thoroughly investigated to the best of our knowledge.