Over saturation behavior of SiPMs at high photon exposure

TL;DR

This study investigates the saturation behavior of Silicon Photomultipliers (SiPMs) under high photon exposure, revealing unexpected output exceeding theoretical limits and incomplete saturation at high intensities.

Contribution

The paper provides experimental evidence of SiPM over saturation phenomena at high photon flux, challenging existing models of their response.

Findings

SiPM output exceeds expected maximum at high photon exposure.

Response deviates significantly from trivial expected behavior.

Saturation is incomplete even at 500 times the number of pixels.

Abstract

Several types of Silicon Photomultipliers were exposed to short pulsed laser light (~ 30 ps FWHM) with its intensity varying from single photon to well above the number of microcells of the device. We observed a significant deviation of the output of SiPMs from the expected behavior although such response curve is considered to be rather trivial. We also noticed that the output exceeds the maximum expected pulse height, which should be defined as the total number of pixels times the single photon pulse height. At the highest light intensity (~ 500 times the number of pixels) that we tested, the signal output reached up to twice the maximum theoretical pulse height, and still did not fully saturate.