Abstract

The integration of silicon nitride (SiN) waveguides into silicon (Si) photonic platforms extends Si photonic integrated circuits (PICs) to visible-light applications including quantum information [1], neurotechnology [2] and miniaturized display systems [3]. Si photodetectors (PDs) are essential components in such systems. Although conventional Si PDs rely on surface incidence-based free space detection, waveguide-coupled PDs are preferred in PICs due to their integrability with other PIC components. In [4], our group reported ultra-broadband SiN-on-Si waveguide PIN and PN PDs operating at λ=400-640nm with an external quantum efficiency of >60% [4]. Such performance opens the possibility for single-photon avalanche diode (SPAD) operation. Although there are several examples of free-space SPADs (λ=490nm) [5] and waveguide-coupled SPADs (λ=1310nm) [6], here we report the preliminary characterization of, to best of our knowledge, the first monolithically integrated waveguide-coupled visible-light SPAD.

© 2023 IEEE