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Proceedings Paper

Waveguide-excited fluorescence microarray
Author(s): Gabriel Sagarzazu; Mélanie Bedu; Lucio Martinelli; Khoi-Nguyen Ha; Nicolas Pelletier; Viatcheslav I. Safarov; Claude Weisbuch; Thierry Gacoin; Henri Benisty
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Paper Abstract

Signal-to-noise ratio is a crucial issue in microarray fluorescence read-out. Several strategies are proposed for its improvement. First, light collection in conventional microarrays scanners is quite limited. It was recently shown that almost full collection can be achieved in an integrated lens-free biosensor, with labelled species hybridizing practically on the surface of a sensitive silicon detector [L. Martinelli et al. Appl. Phys. Lett. 91, 083901 (2007)]. However, even with such an improvement, the ultimate goal of real-time measurements during hybridization is challenging: the detector is dazzled by the large fluorescence of labelled species in the solution. In the present paper we show that this unwanted signal can effectively be reduced if the excitation light is confined in a waveguide. Moreover, the concentration of excitation light in a waveguide results in a huge signal gain. In our experiment we realized a structure consisting of a high index sol-gel waveguide deposited on a low-index substrate. The fluorescent molecules deposited on the surface of the waveguide were excited by the evanescent part of a wave travelling in the guide. The comparison with free-space excitation schemes confirms a huge gain (by several orders of magnitude) in favour of waveguide-based excitation. An optical guide deposited onto an integrated biosensor thus combines both advantages of ideal light collection and enhanced surface localized excitation without compromising the imaging properties. Modelling predicts a negligible penalty from spatial cross-talk in practical applications. We believe that such a system would bring microarrays to hitherto unattained sensitivities.

Paper Details

Date Published: 2 May 2008
PDF: 8 pages
Proc. SPIE 6991, Biophotonics: Photonic Solutions for Better Health Care, 699123 (2 May 2008); doi: 10.1117/12.781297
Show Author Affiliations
Gabriel Sagarzazu, Genewave (France)
Mélanie Bedu, Genewave (France)
Lucio Martinelli, Genewave (France)
Khoi-Nguyen Ha, Genewave (France)
Nicolas Pelletier, Genewave (France)
Viatcheslav I. Safarov, Genewave (France)
Claude Weisbuch, Lab. de Physique de la Matière Condensée, Ecole Polytechnique (France)
Thierry Gacoin, Lab. de Physique de la Matière Condensée, Ecole Polytechnique (France)
Henri Benisty, Lab. Charles Fabry, Institut d'Optique Graduate School (France)

Published in SPIE Proceedings Vol. 6991:
Biophotonics: Photonic Solutions for Better Health Care
Jürgen Popp; Wolfgang Drexler; Valery V. Tuchin; Dennis L. Matthews, Editor(s)

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