A 4 × 128 SPAD array with a 78-ps 512-channel TDC for time-gated pulsed Raman spectroscopy

Abstract

A time-gated 4 9 128 single photon avalanche diode (SPAD) line array with a 512-channel time-to-digital converter (TDC) has been designed and fabricated in a 0.35 lm high voltage CMOS technology for pulsed Raman spectroscopy. In Raman spectroscopy the SPAD array can be designed as a line array with a high fill factor because the electronics can be placed on either side of it. The resolution of the designed TDC is 80 ps in the first four bins, to achieve an accurate time position of the Raman photons, while the last four bins are increased in width to achieve a larger dynamic range. The measured standard deviation of the variation in the width of the first four bins of the 512-channel TDC was less than 10 ps. In addition, crosstalk measurements were carried out to investigate the probability of cross-talk between adjacent SPADs in an array of high density. These showed a cross-talk probability of 0.12 % with a pitch of 32 lm between adjacent SPADs. The highest probability of cross-talk was found to occur with a short delay.

Time-zoomable FRET spectroscopy with a 512 x16 SPAD line sensor

“…The per-pixel time-resolution offered by SPAD line sensors opens up new applications in hyperspectral scanning systems in microscopy, endoscopy as well as new modalities in FRET, fluorescence lifetime and Raman spectroscopies. 1,5,6,7 A major drawback of TCSPC systems is the need to readout time-stamp information for each detected photon requiring a high output data rate which limits the maximum operating frequency. 5 Time-gated measurement can be used to lower data rates through detecting photons in two or more time-windows to extract fluorescence life-times.…”

“…5 Time-gated measurement can be used to lower data rates through detecting photons in two or more time-windows to extract fluorescence life-times. Several architectures have been proposed to address such challenges from 4 gated counters 5 , per-pixel time to digital converters (TDCs) 6 , time-gated memories 7 , in-pixel center-of-mass computation 1 , and off-chip FPGA TDCs. 8 In this work we exploit a recently developed 512 x 16 x 2 line sensor array for time-resolved fluorescence spectroscopy which supplements the generation of TCSPC time-codes with on-chip histogramming functionality for each pixel, greatly increasing sensor throughput.…”

Effects of the inhomogeneity of the time resolving CMOS single-photon avalanche diode array on time-gated Raman spectroscopy

“…The SPAD is well-suited for Raman spectroscopy because it can detect single photons and thus a weak Raman scattering can be detected and additionally, the time gating can be constructed in the same die with a SPAD quite easily compared to ICCDs and CCDs without any cooling. Several other groups have also presented SPADs and SPAD arrays for time-gated Raman spectroscopy [17][18][19][20]. As has been shown, SPADs are suitable for array structures where the time gating electronics with a timing resolution of hundreds of picoseconds can be realized in the same die [19,20].…”

“…Several other groups have also presented SPADs and SPAD arrays for time-gated Raman spectroscopy [17][18][19][20]. As has been shown, SPADs are suitable for array structures where the time gating electronics with a timing resolution of hundreds of picoseconds can be realized in the same die [19,20]. To achieve adequate fluorescence suppression with a high fluorescence background having lifetimes of several nanoseconds, a time gate width of hundreds of picoseconds or less is required.…”

A CMOS SPAD Line Sensor With Per-Pixel Histogramming TDC for Time-Resolved Multispectral Imaging

“…achieved. Several architectures have been explored in the literature including gated counters [2], time-gated memories [4], in-pixel center-of-mass computation [5], [6], per-pixel time-to-digital converters (TDCs) [3], column parallel flash TDCs [7], multi-event folded flash TDCs [8], off-chip FPGA TDCs [9], and on-chip histogramming [10], [11].…”