Distortions from Multi-photon Triggering in a Single CMOS SPAD

Motivated by the need for correct characterization and operation of single-photon avalanche diodes (SPADs), three methods for discriminating between singleand multi-photon triggering in a single CMOS SPAD are compared. The first method, utilizing a measurement of the avalanche’s quench time, correctly distinguishes between avalanches initiated by one photon or 100 incident photons with p > 0.80 in single-shot measurements. The second method, which modulates the detector efficiency, correctly distinguished streams of pulses with single photons or 100 photons with p > 0.99, but is unable to provide a single-shot measurement. The third method, which examines distortions to the timing jitter’s diffusion tail, requires knowledge of the incident timing jitter a priori and is unlikely to be useful in most systems. All compared methods are independent of one another, and show promise for distinguishing how many photons seed an avalanche.