Above pile-up fluorescence microscopy with a 32 Mc/s single-channel time-resolved SPAD system

One of the major drawbacks of time-correlated single-photon counting (TCSPC) is generally represented by pile-up distortion, which strongly bounds the maximum acquisition speed to a few percent of the laser excitation rate. Based on a previous theoretical analysis, recently we presented the first, to the best of our knowledge, low-distortion and high-speed TCSPC system capable of overcoming the pile-up limitation by perfectly matching the single-photon avalanche diode (SPAD) dead time to the laser period. In this work, we validate the proposed system in a standard fluorescence measurement by comparing experimental data with the reference theoretical framework. As a result, a count rate of 32 Mc/s was achieved with a single-channel system still observing a negligible lifetime distortion.