Acconcia Giulia, Cominelli Alessandro, Ghioni Massimo, Rech Ivan
Opt Express. 2018 Jun 11;26(12):15398-15410. doi: 10.1364/OE.26.015398.
Time-Correlated Single Photon Counting (TCSPC) is an essential tool in many scientific applications, where the recording of optical pulses with picosecond precision is required. Unfortunately, a key issue has to be faced: distortion phenomena can affect TCSPC experiments at high count rates. In order to avoid this problem, TCSPC experiments have been commonly carried out by limiting the maximum operating frequency of a measurement channel below 5% of the excitation frequency, leading to a long acquisition time. Recently, it has been demonstrated that matching the detector dead time to the excitation period allows to keep distortion around zero regardless of the rate of impinging photons. This solution paves the way to unprecedented measurement speed in TCSPC experiments. In this scenario, the front-end circuits that drive the detector play a crucial role in determining the performance of the system, both in terms of measurement speed and timing performance. Here we present two fully integrated front-end circuits for Single Photon Avalanche Diodes (SPADs): a fast Active Quenching Circuit (AQC) and a fully-differential current pick-up circuit. The AQC can apply very fast voltage variations, as short as 1.6ns, to reset external custom-technology SPAD detectors. A fast reset, indeed, is a key parameter to maximize the measurement speed. The current pick-up circuit is based on a fully differential structure which allows unprecedented rejection of disturbances that typically affect SPAD-based systems at the end of the dead time. The circuit permits to sense the current edge resulting from a photon detection with picosecond accuracy and precision even a few picoseconds after the end of the dead time imposed by the AQC. This is a crucial requirement when the system is operated at high rates. Both circuits have been deeply characterized, especially in terms of achievable measurement speed and timing performance.
时间相关单光子计数（TCSPC）是许多科学应用中的一项重要工具，这些应用需要以皮秒精度记录光脉冲。不幸的是，必须面对一个关键问题：在高计数率下，失真现象会影响TCSPC实验。为了避免这个问题，TCSPC实验通常通过将测量通道的最大工作频率限制在激发频率的5%以下来进行，这导致采集时间很长。最近，已经证明使探测器死时间与激发周期相匹配可以使失真保持在零左右，而与入射光子的速率无关。这种解决方案为TCSPC实验带来了前所未有的测量速度。在这种情况下，驱动探测器的前端电路在决定系统性能方面起着关键作用，无论是在测量速度还是定时性能方面。在这里，我们展示了两种用于单光子雪崩二极管（SPAD）的完全集成前端电路：一种快速有源猝灭电路（AQC）和一种全差分电流拾取电路。AQC可以施加非常快速的电压变化，短至1.6纳秒，以重置外部定制技术的SPAD探测器。实际上，快速重置是最大化测量速度的关键参数。电流拾取电路基于全差分结构，这允许前所未有地抑制通常在死时间结束时影响基于SPAD的系统的干扰。即使在AQC施加的死时间结束后几皮秒，该电路也能以皮秒精度和准确度感测由光子检测产生的电流边沿。当系统以高速率运行时，这是一项关键要求。这两种电路都经过了深入的表征，特别是在可实现的测量速度和定时性能方面。
