Telecoms-wavelength SPDC in femtosecond-laser-written PPLN waveguides

We have optimised the design and fabrication of low-loss type-I femtosecond-laser-written waveguides in PPLN that are single-transverse mode at 780 nm and 1560 nm and mode-matched to single-mode fibres. Spontaneous parametric downconversion (SPDC) has been demonstrated at 1560 nm when pumped with a 780 nm DFB laser and has been characterised with measurement of the second-order cross-correlation g(2) using superconducting nanowire detectors. This novel approach to waveguide fabrication in PPLN offers routes to high levels of integration and high generation rates which is important for many quantum-information applications.