Absolute absorption cross-section measurement of a submonolayer film on a silica microresonator

Year: 2014

Authors: Barnes Jack A., Gagliardi G., Loock H.-P.

Autors Affiliation: Department of Chemistry, Queen’s University, Kingston, Ontario K7L 3N6, Canada;
Consiglio Nazionale delle Ricerche-Istituto Nazionale di Ottica (INO), Comprensorio “A. Olivetti,” Via Campi Flegrei 34, 80078 Pozzuoli (Naples), Italy

Abstract: Conventional absorption spectroscopy is not nearly sensitive enough for quantitative overtone measurements on submonolayer coatings. While cavity-enhanced absorption detection methods using microresonators have the potential to provide quantitative absorption cross sections of even weakly absorbing submonolayer films, this potential has not yet been fully realized. To determine the absorption cross section of a submonolayer film of ethylene diamine (EDA) on a silica microsphere resonator, we use phase-shift cavity ringdown spectroscopy simultaneously on near-IR radiation that is Rayleigh backscattered from the microsphere and transmitted through the coupling fiber taper. We then independently determine both the coupling coefficient and the optical loss within the resonator. Together with a coincident measurement of the wavelength frequency shift, an absolute overtone absorption cross section of adsorbed EDA, at submonolayer coverage, was obtained and was compared to the bulk value. The smallest quantifiable absorption cross section is sigma(min) = 2.7 x 10(-12) cm(2). This absorption cross section is comparable to the extinction coefficients of, e.g., single gold nanoparticles or aerosol particles. We therefore propose that the present method is also a viable route to absolute extinction measurements of single particles. (C) 2014 Optical Society of America

Journal/Review: OPTICA

Volume: 1 (2)      Pages from: 75  to: 83

More Information: Funding Agency: Consiglio Nazionale delle Ricerche; Natural Sciences and Engineering Research Council of Canada (NSERC).
KeyWords: Absorption spectroscopy; Ethylene; Microspheres; Silica, Absorption cross sections; Cavity enhanced absorption; Cavity ring-down spectroscopy; Conventional absorption; Extinction coefficients; Extinction measurements; Microoptical devices; Submonolayer coverage; Resonators
DOI: 10.1364/OPTICA.1.000075

Citations: 13
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