256 × 2 SPAD line sensor for time resolved fluorescence spectroscopy

Nikola Krstajic, James Levitt, Simon P. Poland, Simon Ameer-Beg, Robert Henderson

Research output: Contribution to journalArticlepeer-review


We present a CMOS chip 256 × 2 single photon avalanche diode
(SPAD) line sensor, 23.78 μm pitch, 43.7% fill factor, custom designed for
time resolved emission spectroscopy (TRES). Integrating time-to-digital
converters (TDCs) implement on-chip mono-exponential fluorescence
lifetime pre-calculation allowing timing of 65k photons/pixel at 200 Hz line
rate at 40 ps resolution using centre-of-mass method (CMM). Per pixel
time-correlated single-photon counting (TCSPC) histograms can also be
generated with 320 ps bin resolution. We characterize performance in terms
of dark count rate, instrument response function and lifetime uniformity for
a set of fluorophores with lifetimes ranging from 4 ns to 6 ns. Lastly, we
present fluorescence lifetime spectra of multicolor microspheres and skin
autofluorescence acquired using a custom built spectrometer. In TCSPC
mode, time-resolved spectra are acquired within 5 minutes whilst in CMM
mode spectral lifetime signatures are acquired within 2 ms for fluorophore
in cuvette and 200 ms for skin autofluorescence. We demonstrate CMOS
line sensors to be a versatile tool for time-resolved fluorescence
spectroscopy by providing parallelized and flexible spectral detection of
fluorescence decay.
Original languageEnglish
Pages (from-to)5653-5669
Number of pages17
JournalOptics Express
Issue number5
Publication statusPublished - 9 Mar 2015

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