Title: Resonant absorption in dielectric thin films for humidity sensing

Authors: Madhuri Kumari; Boyang Ding; Richard J. Blaikie

Addresses: Department of Physics, MacDiarmid Institute for Advanced Materials and Nanotechnology, University of Otago, Dunedin, 9016, New Zealand ' Department of Physics, MacDiarmid Institute for Advanced Materials and Nanotechnology, University of Otago, Dunedin, 9016, New Zealand ' Department of Physics, MacDiarmid Institute for Advanced Materials and Nanotechnology, University of Otago, Dunedin, 9016, New Zealand

Abstract: We have designed and fabricated novel humidity sensors based on thin-film systems capable of sustaining optical resonances in subwavelength thick absorbing dielectric coatings on reflecting surfaces, as a result of coupling between molecular absorption and Fabry-Perot resonances. Specifically, our experiments demonstrate that a strong resonance can be observed in the reflection spectrum of a 105 nm thick Rhodamine 6G-doped polyvinyl alcohol (PVA) coating on a silver surface under certain illumination conditions; this resonance shows an excellent spectral and temporal sensitivity to the change of environmental humidity. In addition, we also demonstrate the humidity sensing potential of a 47 nm thick titanium dioxide coating on an aluminium substrate as a more robust system for practical implementation.

Keywords: titanium dioxide; TiO2 coatings; polyvinyl alcohol; PVA coatings; resonant absorption; dielectric thin films; humidity sensing; humidity sensors; sensor design; aluminium substrate; optical resonances; molecular absorption; Fabry-Perot resonances; silver surfaces.

DOI: 10.1504/IJNT.2017.082466

International Journal of Nanotechnology, 2017 Vol.14 No.1/2/3/4/5/6, pp.204 - 212

Published online: 21 Feb 2017 *

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