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Proceedings Paper

Relative humidity sensing using dye-doped polymer thin-films on metal substrates
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Paper Abstract

We demonstrate humidity sensors based on optical resonances sustained in sub-wavelength thick dye-doped polymer coatings on reflecting surfaces. As a result of coupling between dye molecular absorption and Fabry-Perot resonances in the air-coating-surface cavity, the absorption spectra of such thin-film structures show a strong resonant peak under certain illumination conditions. These resonances are sensitive to the structural and material properties of the thin-film, metal underlayer and ambient conditions and hence can be used for gas and vapor sensing applications. Specifically, we present our proof of principle experimental results for humidity sensing using a thin-film structure comprising Rhodamine6G-doped polyvinyl alcohol (PVA) films on silver substrates. Depending on the PVA film thickness, dye-concertation and angle of incidence, the resonant absorption peak can undergo either red-shift or blue-shift as RH level increases in the range 20% to 60%. Also, the absorption magnitude at certain wavelengths near to resonance show almost linear reduction which can be used as the sensing signal. Our simulation studies show a very good agreement with the experimental data. The spectral and temporal sensitivity of this thin-film structure is attributed to the changes in the thickness of the PVA layer which swells by absorbing water molecules

Paper Details

Date Published: 22 December 2015
PDF: 9 pages
Proc. SPIE 9668, Micro+Nano Materials, Devices, and Systems, 96680T (22 December 2015); doi: 10.1117/12.2201167
Show Author Affiliations
Madhuri Kumari, Univ. of Otago (New Zealand)
Boyang Ding, Univ. of Otago (New Zealand)
Richard Blaikie, Univ. of Otago (New Zealand)


Published in SPIE Proceedings Vol. 9668:
Micro+Nano Materials, Devices, and Systems
Benjamin J. Eggleton; Stefano Palomba, Editor(s)

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