Interfacing a laser-written programmable photonic integrated circuit with a silicon SPAD array

Integrating both manipulation and detection in the same device is essential for the scalability of single-photon processing systems, but achieving high performance through monolithic integration is challenging. With this work, we propose the direct coupling of a programmable photonic integrated circuit, manufactured by femtosecond laser waveguide writing in glass, to a silicon single-photon avalanche diode array, fabricated by using a planar custom technology. We show a compact device featuring a system detection efficiency (i.e. including both circuit and detector losses) of up to 41.0% at 561 nm, assembled with a method that is tolerant to misalignments and compatible with programmable multimode photonic circuits.