1,721,042 research outputs found
A 4.5 ps precision TCSPC system: design principles and characterization
Get PDFWith the recent advancements in single-photon detectors, very low-jitter timing systems are required to fully exploit their performance in real applications. In this article, we present the design principles and experimental characterization of a single-channel time-correlated single-photon counting (TCSPC) system, that achieves a jitter down to 4.5 ps FWHM, a peak-to-peak differential nonlinearity of 1.5 % LSB and a count rate of 12 Mcps over a nanoseconds full-scale range. These results have been attained by minimizing the different jitter contributions that are introduced at various levels in the whole timing chain, still without trading them off with the other performance parameters. To the best of our knowledge, this work represents the state-of-the-art performance in case of a full-scale range as large as 12.5 ns
Toward ultra-fast time-correlated single-photon counting: A compact module to surpass the pile-up limit
Get PDFTime-Correlated Single-Photon Counting (TCSPC) is an excellent technique used in a great variety of scientific experiments to acquire exceptionally fast and faint light signals. Above all, in Fluorescence Lifetime Imaging (FLIM), it is widely recognized as the gold standard to record sub-nanosecond transient phenomena with picosecond precision. Unfortunately, TCSPC has an intrinsic limitation: to avoid the so-called pile-up distortion, the experiments have been historically carried out, limiting the acquisition rate below 5% of the excitation frequency. In 2017, we demonstrated that such a limitation can be overcome if the detector dead time is exactly matched with the excitation period, thus paving the way to unprecedented speedup of FLIM measurements. In this paper, we present the first single-channel system that implements the novel proposed methodology to be used in modern TCSPC experimental setups. To achieve this goal, we designed a compact detection head, including a custom single-photon avalanche diode externally driven by a fully integrated Active Quenching Circuit (AQC), featuring a finely tunable dead time and a short reset time. The output timing signal is extracted by using a picosecond precision Pick-Up Circuit (PUC) and fed to a newly developed timing module consisting of a mixed-architecture Fast Time to Amplitude Converter (F-TAC) followed by high-performance Analog-to-Digital Converters (ADCs). Data are transmitted in real-time to a Personal Computer (PC) at USB 3.0 rate for specific and custom elaboration. Preliminary experimental results show that the new TCSPC system is suitable for implementing the proposed technique, achieving, indeed, high timing precision along with a count rate as high as 40 Mcps
32ps timing jitter with a fully integrated front end circuit and single photon avalanche diodes
Get PDFExcellent performance of custom technology SPAD detectors have been widely demonstrated in recent years. Low-jitter timing measurements with these detectors require front end electronics able to sense the avalanche current at a very low level when the multiplication process is still confined in a very small area around the photon absorption point. Best in class results (35 ps full width at half maximum) have been obtained with discrete circuits not suitable to be used in densely integrated systems of SPAD arrays required by modern demanding applications. A new fully integrated front end able to read out the avalanche current with a timing jitter as low as 32 ps and suitable to be exploited with SPAD arrays is presented
Fast time-correlated single photon counting system to overcome pile-up limitation with single photon avalanche diodes
No full textTime-Correlated Single Photon Counting (TCSPC) is generally recognized as a powerful tool for Fluorescence Lifetime Imaging (FLIM), thanks to its inherently high sensitivity and timing precision. Nevertheless, one of the major drawbacks of the technique is represented by the so-called pile-up distortion, that typically limits the acquisition rate to few percent of the laser stimulation rate. In recent years, an innovative methodology has been proposed to overcome this restriction: by matching the detector dead time to the laser period an average acquisition rate of 40 Mcps is achieved, along with negligible distortion. In this work, we present the first single-channel system that implements the new measurement technique. To this aim, two modules have been specifically developed to accommodate a custom-technology Single-Photon Avalanche Diode (SPAD) and its dedicated acquisition chain. On one hand, a compact Detection Module hosts both a fully-integrated Active Quenching Circuit (AQC) to provide a finely-tunable dead time and a differential Pick-Up Circuit (PUC) to extract a picosecond-precision timing signal. On the other hand, a Time Conversion module is intended to acquire the fast timing signal thanks to a mixed-architecture Fast Time to Amplitude Converter (F-TAC). The experimental characterization proved that the modules feature excellent performance both in terms of timing precision (55 ps FWHM) and Differential Nonlinearity (4 % LSB peak to peak) and we're now ready to compare the new technique with the classic pile-up limited approach in a real application on field
Modified single photon counting modules for optimal timing performance
No full textA modification of a standard Perkin Elmer SPCM-AQR photon detector module that remarkably improves the photon timing performance is presented here. The modification consists of an additional timing circuit board, which is inserted in the module without modifying the original circuit board. The essential feature is a pulse pickup linear network, connected to the high-voltage terminal of the photodetector, which extracts a short pulse signal with fast rise, coincident with the rise of the avalanche current. The information about the photon arrival time is obtained by sensing the onset of the rise. At low counting rates (<10^5 counts/ s) time-correlated photon counting tests show that the instrumental resolution function (IRF) thus obtained has full width at half maximum (FWHM) narrower by about 40% with respect to the original module. At higher counting rate, up to few Mcounts/s, the advantage is even more remarkable: The timing circuit practically eliminates the drawbacks that plague the original module, namely, a progressive increase of the FWHM and a progressive shift of the peak position of the IRF with increasing counting rate. The modified SPCM-AQR module is therefore suitable also for applications requiring subnanosecond time resolution at high and/or variable counting rate, such as fluorescent decay measurements, fluorescent lifetime imaging, single molecule detection and spectroscopy, and optical radar techniques
A simple and flexible FPGA based autocorrelator for afterpulse characterization of single-photon detectors
No full textSingle Photon Avalanche Diodes (SPADs) are widely employed for photon counting and timing in a variety of scientific and industrial applications. However they are affected by the afterpulsing effect, which can significantly increase the effective dark count rate of the detector. Being correlated with previous photon pulses, afterpulses can cause sharp distortions in photon correlation experiments. In this paper we exploit autocorrelation to characterize the afterpulsing of SPADs. A FPGA based autocorrelator has been specifically designed to this purpose, featuring a lag-time range from 10ns to more than 10ms, covering a range well beyond the longest expected trapped carrier lifetime
10-nanosecond dead time and low afterpulsing with a free-running reach-through single-photon avalanche diode
No full textThe reduction of detector dead time represents an enabling factor in several photon counting applications. In this work, we investigate the free-running operation of reach-through single-photon avalanche diodes (SPADs) at ultra-low dead times. By employing a fast active quenching circuit with direct bonding to the detector, we are able to achieve a 10 ns dead time with a thick SPAD by Excelitas, still maintaining extremely low afterpulsing probabilities (below 1.5%)
A 32-channel photon counting module with embedded auto/cross-correlators for real-time parallel fluorescence correlation spectroscopy
Get PDFFluorescence correlation spectroscopy (FCS) is a well-established technique to study binding interactions or the diffusion of fluorescently labeled biomolecules in vitro and in vivo. Fast FCS experiments require parallel data acquisition and analysis which can be achieved by exploiting a multi-channel Single Photon Avalanche Diode (SPAD) array and a corresponding multi-input correlator. This paper reports a 32-channel FPGA based correlator able to perform 32 auto/cross-correlations simultaneously over a lag-time ranging from 10 ns up to 150 ms. The correlator is included in a 32 × 1 SPAD array module, providing a compact and flexible instrument for high throughput FCS experiments. However, some inherent features of SPAD arrays, namely afterpulsing and optical crosstalk effects, may introduce distortions in the measurement of auto- and cross-correlation functions. We investigated these limitations to assess their impact on the module and evaluate possible workarounds
Overcoming Pile-up Limitation in Fluorescence Lifetime Imaging
No full textWe present the first compact Time-Correlated Single-Photon Counting single-channel system, capable of overcoming the typical pile-up limitation of Fluorescence Lifetime Imaging. An ultra-fast acquisition is obtained (40 Mcps), along with excellent timing results and negligible distortion
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