SiN waveguides for ultra-broadband visible-telecom photon pairs

Abstract Broadband frequency-correlated photon-pair sources could enable the realization of various quantum information technologies especially WDM-QKD (wavelength division multiplexed quantum key distribution) accommodating multiple users with enhanced data transmission rates. The wide transparency window, negligible nonlinear losses, and con- siderable refractive index contrast of silicon nitride (SiN) on insulator (SiO2) platform makes it an ideal material system for designing CMOS- compatible integrated photon sources based on spontaneous four-wave mixing (SFWM). We propose simple rectangular cross-section, few- cm long SiN waveguide designs capable of generating ultra-broadband frequency-correlated photon pairs via SFWM, exceeding an octave in bandwidth spanning the visible-to-telecom wavelengths (∼700-1700nm for ∼1-μm pump) with a spectral brightness of >2.5×10 4 photon pairs/s/nm/mW 2 . Such compact sources, spanning the entire telecom spectrum (across O, E, S, C, L, and U bands) on one side and cover- ing most of the major atomic transitions used in ultracold gases and solid-state based quantum memories on the other side, could poten- tially be employed in large-scale multi channel hybrid (free space + fiber) quantum networking schemes in addition to the heralding of telecom single photons by utilizing high efficiency visible detectors.