keywords ACTIVE-QUENCHING-CIRCUIT DARK COUNT Engineering Engineering, Electrical & Electronic HIGH-SPEED IMAGE SENSOR Optics PET PHOTON AVALANCHE-DIODE Physical Sciences Physics Physics, Applied Quantum Science & Technology RAMAN-SPECTROSCOPY Raman SILICON PHOTOMULTIPLIER Science & Technology Single-photon avalanche diode (SPAD) TDC TIME-OF-FLIGHT TO-DIGITAL CONVERTER Technology fluorescence lifetime imaging (FLIM) imagers positron emission tomography (PET)