SPDC single photon source in Ti-indiffused diced ridge LiNbO3 waveguides

Stable and bright single photon sources are key components for future quantum applications. A simple fabrication method is an important requirement for such sources. Here, we present a single photon source based on diced ridge waveguides in titanium indiffused LiNbO₃. These waveguides can be easily fabricated by combining planar titanium in-diffusion without lithographic patterning and easy-to-handle precision dicing. Such devices have the potential to generate high single photon rates, because ridge structures are typically less prone to the photorefractive effect. We achieve waveguide propagation losses <0.4dB/cm and a SHG conversion efficiency of about 81 %/W/cm². Harnessing a type-0 SPDC process to generate 1550 nm photons, we obtain a SPDC brightness of 3·10⁵ 1/(s mW nm), with a heralding efficiency of η_h=45 % (η_h=77.5 % for the waveguide itself excluded setup losses) and a heralded second-order correlation function of g²_h(0)<0.003 at low pump powers.