Towards high-speed low-distortion time-correlated single photon counting measurements

The Time Correlated Single Photon Counting (TCSPC) technique represents a key tool in many fields where picosecond precision is required to record fast and faint luminous signals. Unfortunately, TCSPC experiments involve a relatively long acquisition time to accumulate a statistically relevant number of events. Indeed, the maximum operating rate of a single acquisition channel is usually kept below 5% of the excitation frequency in order to guarantee an acceptable pileup distortion. In this work, we propose a novel technique to speed up TCSPC experiments by almost an order of magnitude, avoiding at the same time any distortion of the recorded curve. First of all, we demonstrate that zero-distortion operation is feasible if an extremely fast conversion electronics is used and the dead time of the detector is matched to the excitation period. In this scenario, the excitation power can be increased well above the pile-up limit, thus enabling unprecedented measurement speed. It is worth highlighting that our technique can be easily extended to a multichannel approach to further speed up the measurement. We also discuss that a practical use of our solution is already feasible exploiting recently-proposed time-measurement circuits with negligible dead time and a Single Photon Avalanche Diode coupled to a fast Active Quenching Circuit, featuring a short and finely tunable dead time. We provide a deep theoretical analysis of the technique to show its potential; in addition, the main issues related to nonidealities of a practical implementation have been widely investigated by means of numerical simulations.