Development and characterization of an 8×8 SPAD-array module for gigacount per second applications

In recent years the development of Single-Photon Avalanche Diodes (SPADs) had a big impact on single-photon counting applications requiring high-performance detectors in terms of Dark Count Rate (DCR), Photon Detection Efficiency (PDE), afterpulsing probability, etc. Among these, it is possible to find applications in single-molecule fluorescence spectroscopy that suffer from long-time measurements. In these cases SPAD arrays can be a solution in order to shorten the measurement time, thanks to the high grade of parallelism they can provide. Moreover, applications in other fields (e.g. astronomy) demand for large-area single-photon detectors, able also to handle very high count rates. For these reasons we developed a new single-photon detection module, featuring an 8 × 8 SPAD array. Thanks to a dedicated silicon technology, the performance of the detector have been finely optimized, reaching a 49% detection efficiency at 550 nm, as well as low dark counts (2 kcount/s maximum all over the array). This module can be used in two different modes: the first is a multi-spot configuration, allowing the acquisition of 64 optical signals at the same time and considerably reducing the time needed for a measurement. The second operation mode instead exploits all the pixels in a combined mode, allowing the detection of a 64-times higher maximum photon rate (up to 2 Gcount/s). In addition, this configuration provides also an extended dynamic range and allows to attain photon number resolving capabilities. Dark counts, detection efficiency, linearity, afterpulsing and crosstalk probability have been characterized at different operating conditions.