Beyond pile-up limits in Time Correlated Single Photon Counting: a new approach

The Time Correlated Single Photon Counting (TCSPC) technique has gained a prominent role in the analysis of fast and faint optical signals. Nonetheless, it has been historically considered an intrinsically slow technique due to its repetitive nature combined with a strict constraint on the maximum detector count rate to avoid distortion. Indeed, classic TCSPC theory states that low (preferably negligible) distortion can be achieved only by limiting the single-photon detector count rate down to few percent (typically 1-5%) of the laser excitation rate[1]. In 2017, we demonstrated an alternative path to avoid distortion in TCSPC based on matching the detector dead time to the excitation period. This approach still limits the speed, preventing the exploitation of the fastest single photon detectors, e.g. Single Photon Avalanche Diodes with a dead time of a few nanoseconds. In this work, we present the experimental validation of a novel TCSPC methodology [2] showing how it is possible to remove all constraints (power, dead time, etc). and still get a negligible level of distortion. This approach opens the way to unprecedented speed in TCSPC measurements