Peronio P, Acconcia G, Rech I, Ghioni M
Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano, Italy.
Rev Sci Instrum. 2015 Nov;86(11):113101. doi: 10.1063/1.4934812.
Time-Correlated Single Photon Counting (TCSPC) has been long recognized as the most sensitive method for fluorescence lifetime measurements, but often requiring "long" data acquisition times. This drawback is related to the limited counting capability of the TCSPC technique, due to pile-up and counting loss effects. In recent years, multi-module TCSPC systems have been introduced to overcome this issue. Splitting the light into several detectors connected to independent TCSPC modules proportionally increases the counting capability. Of course, multi-module operation also increases the system cost and can cause space and power supply problems. In this paper, we propose an alternative approach based on a new detector and processing electronics designed to reduce the overall system dead time, thus enabling efficient photon collection at high excitation rate. We present a fast active quenching circuit for single-photon avalanche diodes which features a minimum dead time of 12.4 ns. We also introduce a new Time-to-Amplitude Converter (TAC) able to attain extra-short dead time thanks to the combination of a scalable array of monolithically integrated TACs and a sequential router. The fast TAC (F-TAC) makes it possible to operate the system towards the upper limit of detector count rate capability (∼80 Mcps) with reduced pile-up losses, addressing one of the historic criticisms of TCSPC. Preliminary measurements on the F-TAC are presented and discussed.
时间相关单光子计数（TCSPC）长期以来一直被认为是测量荧光寿命最灵敏的方法，但通常需要“较长”的数据采集时间。这一缺点与TCSPC技术的计数能力有限有关，这是由堆积和计数损失效应导致的。近年来，多模块TCSPC系统已被引入以克服这一问题。将光分成连接到独立TCSPC模块的几个探测器，按比例增加了计数能力。当然，多模块操作也会增加系统成本，并可能导致空间和电源问题。在本文中，我们提出了一种基于新型探测器和处理电子设备的替代方法，旨在减少整个系统的死时间，从而能够在高激发速率下进行高效的光子采集。我们展示了一种用于单光子雪崩二极管的快速有源猝灭电路，其最小死时间为12.4纳秒。我们还介绍了一种新型时间幅度转换器（TAC），由于单片集成TAC的可扩展阵列和顺序路由器的组合，它能够实现极短的死时间。快速TAC（F-TAC）使系统能够在堆积损失减少的情况下朝着探测器计数率能力的上限（约80兆计数每秒）运行，解决了TCSPC长期以来的一个批评问题。本文展示并讨论了对F-TAC的初步测量结果。
