Mechanism causing the spatial distribution non-uniformity of the prompt optical crosstalk effect in G-APD cells of silicon photomultipliers

The optical crosstalk effect in Silicon Photomultipliers (SiPM) is unnecessary parasitic effects. The mechanism leading to the non-uniform spatial distribution of the prompt optical crosstalk in SiPMs was investigated in detail herein. The experimental results showed that the optical crosstalk probability (Pct) in SiPMs without optical isolation trenches was clearly non-uniform within the Geiger-mode avalanche photodiode (G-APD) cell. However, the spatial distribution uniformity of Pct in G-APD cells was improved significantly in an SiPM containing optical isolation trenches. The different propagation distances of crosstalk photons emitted from different positions of the source G-APD cell to the nearest neighboring G-APD cell along a straight line, were the main reason for the non-uniform spatial distribution of Pct in the SiPM. According to the experimental results, it can also be inferred that the emission of crosstalk photons is spatially localized during a G-APD cell’s avalanche event, and majority crosstalk photons are emitted during the early stage of the avalanche.