Interfacing photonic building blocks for silicon nitride photonic-integrated circuit-based sensing devices

Silicon nitride waveguide based photonic integrated circuits (PICs) are intensively investigated for a wide range of sensing applications in the visible to sub 1-µm near-infrared spectral region. The monolithic co-integration of silicon photodiodes and read-out electronics offers additional benefits in terms of performance and miniaturization. We discuss challenging aspects related to the efficient coupling and routing of light to, from, and within PICs and present interfacing photonic building blocks offering potential solutions. We demonstrate the suitability of these interfacing building blocks by using them for the realization of a PIC-based multi-channel optical coherence tomography concept at 840 nm.