Teaching single-photon detection metrology with off-the-shelf CMOS SPAD detectors

The fabrication of the first CMOS single-photon avalanche diodes (SPADs) back in 2003 paved the way to a range of photodetection applications based on single-photon detection, photon counting, and photon time-stamping. In turn, it has become more and more important to teach the subject at the undergraduate and graduate levels, and to illustrate key underlying concepts, such as photon detection probability (PDP), dead time, timing jitter, and dark count rate (DCR), by means of new and existing hardware. We have therefore introduced at EPFL AQUA a series of lab practicals based on a credit card-sized off-the-shelf array of CMOS SPADs, known as SPAD23, to complement our existing Metrology graduate class. The sensor consists of 23 independent devices, individually connected to an FPGA that provides a user-friendly user interface, including time-tagging capabilities with 20 ps resolution and an instrument response function (IRF) of ~100 ps FWHM. Access to the raw data is provided and there is no risk of damaging the detector.