Characterization of Single-Photon Time Resolution: From Single SPAD to Silicon Photomultiplier

In this paper, we report on the characterization of the single-photon time resolution (SPTR) of the RGB (Red-Green-Blue) type silicon photomultipliers (SiPM) produced at FBK. We measured and compared single-photon timing jitter of 1 ×1 mm² and 3 ×3 mm² SiPMs, and also of square SPADs with integrated passive quenching, identical to the cells composing the SiPMs. We reached a single-photon time resolution of about 180 ps full-width at half-maximum for 3 ×3 mm² SiPM, 80 ps for 1 ×1 mm² SiPM and less than 50 ps for single cells. From measurements with pinholes placed in front of 1 ×1 mm² detector we see a very good cell-to-cell uniformity: it is not a limiting factor for time resolution. We also characterized the timing jitter of SiPMs as a function of the number of photons per laser pulse (N) finding that it does not decrease exactly with the square root of N because of the optical crosstalk between cells.