Mechanism causing the spatial distribution non- uniformity of the prompt optical crosstalk effect in G- APD cells of Multi-Pixel Photon Counters

Abstract The optical crosstalk effect in Multi-Pixel Photon Counters (MPPC) is unnecessary parasitic effects. The mechanism leading to the non-uniform spatial distribution of the prompt optical crosstalk in MPPCs was investigated in detail herein. The experimental results showed that the optical crosstalk probability (P ct ) in MPPCs without optical isolation trenches was clearly non-uniform within the Geiger-mode avalanche photodiode (G-APD) cell. However, the spatial distribution uniformity of P ct in G-APD cells was improved significantly in an MPPC 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 P ct in the MPPC. 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.