A fibre-integrated SPDC heralded single-photon source using Zn-indiffused LiNbO₃ ridge waveguides at telecom wavelengths

We present a compact, fibre-integrated source of telecom-band photon pairs based on a commercial Zn-indiffused PPLN ridge waveguide. Operated in Type-0 degenerate SPDC, the device generates an exceptionally wide emission spanning ∼ 90 nm and exhibits strong nonclassical correlations. Using superconducting nanowire detectors, we record a normalised pair-generation rate of 9.1 × 10⁹ s⁻¹ mW⁻¹, a coincidences-to-accidentals ratio (CAR) exceeding 9 × 10⁴, and a heralded second-order correlation of g⁽²⁾_h (0) ≈ 5 × 10⁻⁴. These results demonstrate that fibre-pigtailed PPLN ridge devices can provide high-purity, broadband single-photon states suitable for wavelength-multiplexed quantum communication.