title: Quantitative analysis of enhanced light irradiance in waveguide-based fluorescent microarrays.
abstract: Probing microarray assays in the presence of a hybridization mix retrieves precious information on hybridization kinetics. However, in common detection schemes, useful surface signals compete with the high supernatant background from labelled targets in the mix. A known solution consists in exciting specifically the microarray surface with evanescent fields. Configurations using planar optical waveguides to produce such fields are shown here to present also a dramatic excitation irradiance enhancement at the guide/surrounding matter interface. We compare theoretically and experimentally a guided excitation with a classical external excitation. A full electromagnetic analysis predicts an irradiance increase higher than 10(4) for adequately tailored waveguides. We deposited high-index TiO(2) sol-gel waveguides on glass substrates according to best simulations. Quantitative enhancement analysis exploiting actual biological fluorescent spots perfectly confirms the irradiance amplification effect of a thin waveguide. The impact of amplification on the design of biochip readers is discussed since it leaves ample margin for simple and low-cost light couplers, advantageous in affordable readers and sensor systems.
authors.affiliation: Genewave, XTEC, Ecole Polytechnique Campus, 91120 Palaiseau, France.
authors.forename: Gabriel
authors.initials: G
authors.lastname: Sagarzazu
authors.forename: Mélanie
authors.initials: M
authors.lastname: Bedu
authors.forename: Lucio
authors.initials: L
authors.lastname: Martinelli
authors.forename: Nicolas
authors.initials: N
authors.lastname: Pelletier
authors.forename: Viatcheslav I
authors.initials: VI
authors.lastname: Safarov
authors.forename: Claude
authors.initials: C
authors.lastname: Weisbuch
authors.forename: Thierry
authors.initials: T
authors.lastname: Gacoin
authors.forename: Henri
authors.initials: H
authors.lastname: Benisty
mesh_terms: D017076:Computer-Aided Design; D004867:Equipment Design; D019544:Equipment Failure Analysis; D017404:In Situ Hybridization, Fluorescence / Q000295:instrumentation*; D008029:Lighting / Q000295:instrumentation*; D020411:Oligonucleotide Array Sequence Analysis / Q000295:instrumentation*; D012031:Refractometry / Q000295:instrumentation; D015203:Reproducibility of Results; D012542:Scattering, Radiation; D012680:Sensitivity and Specificity; D020349:Surface Plasmon Resonance / Q000295:instrumentation*