Characterization of SiPM Optical Crosstalk and its Dependence on the Protection-Window Thickness

TL;DR

This study investigates how the optical crosstalk in silicon photomultipliers depends on the protection-window thickness, combining experimental measurements with ray-tracing simulations to understand photon propagation effects.

Contribution

It provides the first detailed measurement of OCT in multichannel SiPMs and compares experimental results with simulations to elucidate the influence of protection-window thickness.

Findings

OCT rates depend on protection-window thickness.

Photon propagation inside the resin affects OCT.

Simulation results agree with experimental measurements.

Abstract

Owing to their high photon detection efficiency, compactness, and low operating voltage, silicon photomultipliers (SiPMs) have found widespread application in many fields, including medical imaging, particle physics, and high-energy astrophysics. However, the so-called optical crosstalk (OCT) phenomenon of SiPMs is a major drawback to their adoption. Secondary infrared photons are emitted inside the silicon substrate spontaneously after the avalanche process caused by the primary incident photons, and they can be detected by the surrounding photodiodes. As a result large output pulses that are equivalent to multiple photoelectrons are observed with a certain probability (OCT rate), even for single-photon events, making the charge resolution worse and increasing the rate of accidental triggers by single-photon events in applications such as atmospheric Cherenkov telescopes. In our previous study, we found that the OCT rates of single-channel SiPMs was dependent on the thickness of their protection resin window, which may be explained by photon propagation inside the resin. In the present study, we measured the OCT rate of a multichannel SiPM and those of neighboring channels caused by photon propagation. Both OCT rates were found to be dependent on the protection-window thickness. We report our OCT measurements of a multichannel SiPM and comparisons with a ray-tracing simulation.