Fast fully-integrated front-end circuit to overcome pile-up limits in time-correlated single photon counting with single photon avalanche diodes

Abstract

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.

Asynchronous Single-Photon 3D Imaging

“…Implications and future outlook: Due to their compatibility with mainstream CMOS sensor fabrication lines, the capabilities of SPAD cameras continue to grow rapidly [11,32,12,20,18,1,3]. As a result, the proposed methods, aided by rapid ongoing advances in SPAD technology, will potentially spur wide-spread adoption of single-photon sensors as all-purpose cameras in demanding computer vision and robotics applications, where the ability to perform reliably in both photon-starved and photon-flooded scenarios is critical to success.…”

“…Photon pileup mitigation for SPAD cameras: Perhaps the most widely adopted approach for preventing pileup is attenuation, i.e., optically blocking the total photon flux incident on the SPAD so that only 1-5% of the laser pulses lead to a photon detection [2,3]. 1 Recent work [14,13] has shown that this rule-of-thumb extreme attenuation is too conservative and the optimal operating flux is considerably higher. Various computational [25,14] and hardware [1,3,35] techniques for mitigating pileup have also been proposed.…”

“…1 Recent work [14,13] has shown that this rule-of-thumb extreme attenuation is too conservative and the optimal operating flux is considerably higher. Various computational [25,14] and hardware [1,3,35] techniques for mitigating pileup have also been proposed. These approaches are complementary to the proposed asynchronous acquisition, and can provide further improvements in performance when used in combination.…”

“…In contrast, we use shifting to mitigate pileup and present a theoretically optimal method for choosing the sequence of shifts and durations of the SPAD measurement gates without any prior knowledge of scene depths. Photon-driven acquisition: The photon-driven (or freerunning) mode of operation has been analyzed for FLIM [16,9,1], and recently for LiDAR [28] where a Markov chain model-based iterative optimization algorithm is proposed to recover the incident waveform from the distorted histogram. The focus of these approaches is on designing efficient waveform estimation algorithms.…”

Custom-Technology Single-Photon Avalanche Diode Linear Detector Array for Underwater Depth Imaging

“…For example, a count rate of 120 Mcps and dark count rate of 9 cps at the temperature T = −20 °C has been demonstrated by Ceccarelli et al [ 33 ]. It is important to note that when SPAD detectors fabricated in custom technology are used for time-correlated measurements, external front end and timing electronics are needed [ 34 , 35 , 36 , 37 ], potentially limiting the number of pixels. However, at the same time, a high number of pixels means a high count rate of the module; under such conditions, readout times become significant and may limit the speed of a TCSPC measurement [ 38 ].…”