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Proceedings Paper

Highly parallel SPAD detector for time-resolved lab-on-chip
Author(s): Michele Benetti; Daniele Iori; Lucio Pancheri; Fausto Borghetti; Laura Pasquardini; Lorenzo Lunelli; Cecilia Pederzolli; Lorenzo Gonzo; Gian-Franco Dalla Betta; David Stoppa
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Paper Abstract

Fluorescence lifetime detection is widely used in molecular biology to monitor many cell parameters (such as pH, ion concentrations, etc.) and for an early diagnosis of many pathologies. In a typical fluorescence lifetime experiment a pulsed laser is used to excite the fluorescent dyes and the emitted light is revealed by means of high sensitivity detectors, typically: intensified CCD, PMTs or Single-Photon Avalanche Diodes (SPADs).In this contribute we present a SPAD detector module fabricated in a 0.35μm High Voltage CMOS technology to be used within a lab-on-chip system consisting of a micro-reactor array for bioaffinity assays based on fluorescence markers. The detector module, having a total area of 600 x 900 μm2, can be arranged to build a small pixel array to be directly coupled to the micro-reactors. No emission filters are needed, since the ultra-short laser pulse is cut off in the time domain. The module consists of a 10x10-SPAD array, where each SPAD cell is equipped with dedicated active quenching and recharging circuit. Each cell has a pitch of 26μm with a fill factor of 48%. The SPADs have been binned in order to realize a large photosensitive area detector exhibiting a reasonably low dark count rate (DCR) and reduced dead time, as required in a fast measurement system. A memory has also been implemented in order to enable only low DCR SPADs, so that a total DCR of about 100kHz can be achieved for the whole photosensitive area. The digital output generated by the SPAD array is sent to a time-discriminator stage which allows a time-gated detection of the incident light. Two time-windows have been implemented in this architecture. Their time width is controlled by an on-chip digital PLL locked to the external laser clock whereas the width of the time-windows can be set within the range 500ps-10ns with a resolution of 500ps. Photons detected within each time window are then counted by two 10-bits digital counters. Time-interleaved operation has been implemented to read out the pixel data in parallel with the photon detection phase.

Paper Details

Date Published: 5 May 2010
PDF: 11 pages
Proc. SPIE 7723, Optics, Photonics, and Digital Technologies for Multimedia Applications, 77231Q (5 May 2010); doi: 10.1117/12.854565
Show Author Affiliations
Michele Benetti, Univ. degli Studi di Trento (Italy)
Daniele Iori, Univ. degli Studi di Trento (Italy)
Fondazione Bruno Kessler (Italy)
Lucio Pancheri, Fondazione Bruno Kessler (Italy)
Fausto Borghetti, Fondazione Bruno Kessler (Italy)
Laura Pasquardini, Fondazione Bruno Kessler (Italy)
Lorenzo Lunelli, Fondazione Bruno Kessler (Italy)
Cecilia Pederzolli, Fondazione Bruno Kessler (Italy)
Lorenzo Gonzo, Fondazione Bruno Kessler (Italy)
Gian-Franco Dalla Betta, Univ. degli Studi di Trento (Italy)
David Stoppa, Fondazione Bruno Kessler (Italy)

Published in SPIE Proceedings Vol. 7723:
Optics, Photonics, and Digital Technologies for Multimedia Applications
Peter Schelkens; Touradj Ebrahimi; Gabriel Cristóbal; Frédéric Truchetet; Pasi Saarikko, Editor(s)

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