A Fibre-Integrated SPDC Heralded Single-Photon Source Using Zn-Indiffused PPLN Ridge Waveguides at Telecom Wavelengths

We report a fibre-integrated heralded single-photon source based on a commercial Zn-indiffused MgO:PPLN ridge waveguide operated in Type-0 degenerate spontaneous parametric down-conversion (SPDC). The device emits a broadband spectrum spanning approximately 70 nm across the telecom C-and L-bands, with an absolute brightness of $9.1\times {10}^9$ pairs/(s mW). After accounting for optical losses, we determine an internal heralding efficiency of 58(5)%. The source maintains high purity, exhibiting a coincidences-to-accidentals ratio exceeding $9\times {10}^4$ and a heralded second-order correlation of $g_{\text{h}}^{(2)}(0)=(5.53\pm 0.46)\times {10}^{-4}$. Low multi-photon noise and broadband emission demonstrate the viability of such platforms for wavelength-multiplexed quantum networking.