The mechanism of the spatial distribution non-uniformity of prompt optical crosstalk effect within APD cells in MPPC

Multi-pixel photon counter (MPPC) has been widely used in the field of weak light detection due to their various advantages in recent years. However, their parasitic effects such as optical crosstalk limit their further improvement in photoelectric performance. A deep understanding of the generation and propagation mechanism of optical crosstalk in MPPC is one of the prerequisites for further improving the performance of MPPC. The mechanism of the non-uniform spatial distribution phenomenon of the prompt optical crosstalk effect (POCE) in MPPC was investigated in-depth. The experimental results show that the optical crosstalk probability (Pct) in MPPC without optical isolation trench shows obviously non-uniformity within the avalanche photo diode (APD) cell, nevertheless, for the MPPC with optical isolation trench, the uniformity of spatial distribution of Pct in APD cells is greatly improved. Therefore, the different propagation distances of crosstalk photons emitted from different positions of the source APD cell to the nearest neighbor APD cell along a straight line, are the main reason of non-uniform spatial distribution of Pct in MPPC. According to the experimental results, it can also be inferred that the emission of crosstalk photons is spatially localized during an avalanche of an APD cell, and most of the crosstalk photons are emitted during the early stage of the avalanche. The results of this paper not only have reference value for further understanding the mechanism of optical crosstalk effect in MPPC, but also be beneficial for guiding to optimize the structure and process design of MPPC, and thus improving the performance of MPPC.