Ten years of biophotonics single-photon SPAD imager applications: retrospective and outlook, Multiphoton Microscopy in the Biomedical Sciences XVII

SPAD (single-photon avalanche diode) arrays are single-photon imagers that can provide unparalleled timeresolved sensing performance. Since their inception in standard CMOS technologies (2003), a host of architectures and target applications have been explored, ranging from simple pixel arrays, with off-chip data processing electronics, to fully integrated “smart” imagers with in-pixel time-stamping electronics and/or on-chip data processing fabric. Applications include (endoscopic) FLIM, (multi-beam multiphoton) FLIM-FRET, SPIMFCS, time-resolved Raman, NIROT, super-resolution microscopy, and PET, to name a few. We will review some representative sensors and applications, the corresponding challenges, and provide an outlook on the future of this fascinating technology