High-birefringence direct UV-written waveguides for heralded single-photon sources at telecommunication wavelengths

Direct UV-written waveguides are fabricated in silica-on-silicon with birefringence of $(4.9\pm 0.2)\times {10}^{-4}$, much greater than previously reported in this platform. We show that these waveguides are suitable for the generation of heralded single photons at telecommunication wavelengths by spontaneous four-wave mixing. A pulsed pump field at 1060 nm generates pairs of photons in highly detuned, spectrally uncorrelated modes near 1550 nm and 800 nm. Waveguide-to-fiber coupling efficiencies of 78-91% are achieved for all fields. Waveguide birefringence is controlled through dopant concentration of $\mathrm{G}\mathrm{e}\mathrm{C}{\mathrm{l}}_4$ and $\mathrm{B}\mathrm{C}{\mathrm{l}}_3$ using the flame hydrolysis deposition process. The technology provides a route towards the scalability of silica-on-silicon integrated components for photonic quantum experiments.