Whispering gallery mode micro resonators for multi-parameter sensing applications

Mallik, Arun Kumar, Farrell, Gerald, Ramakrishnan, Manjusha, Kavangal, Vishnu, Liu, Dejun, Wu, Qiang and Semenova, Yuliya (2018) Whispering gallery mode micro resonators for multi-parameter sensing applications. Optics Express, 26 (24). pp. 31829-31838. ISSN 1094-4087

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Official URL: https://doi.org/10.1364/OE.26.031829


A novel fiber optic sensing configuration for simultaneously measuring ammonia vapor (NH3) concentration and relative humidity (RH) in air is proposed and experimentally demonstrated. The system comprised two silica whispering gallery mode (WGM) microsphere resonators coated with different polymer layers. One of the microspheres was dip-coated with sol gel silica polymer and another with a 0.5 % wt./vol. agarose hydrogel. WGMs in both microspheres were excited simultaneously by evanescent coupling using a single adiabatic fiber taper. The optical properties of both coating layers change due to their exposure to ammonia and water molecules in the surrounding atmosphere, resulting in the spectral shifts of the WGM resonances relevant to each of the microspheres. By measuring the relevant WGMs spectral shifts, NH3 concentration in air and RH can be determined simultaneously. The experimentally demonstrated sensitivity of the proposed sensor array to ammonia was estimated as 19.07 pm/ppm (NH3 molecules in air) and its sensitivity to relative humidity as 1.07 pm/% RH. Detailed studies of the coatings cross-sensitivity and temperature dependence are also presented. The proposed sensor array is compact, highly sensitive and potentially low cost.

Item Type: Article
Additional Information: © 2018 Optical Society of America. Users may use, reuse, and build upon the article, or use the article for text or data mining, so long as such uses are for non-commercial purposes and appropriate attribution is maintained. All other rights are reserved.
Subjects: H600 Electronic and Electrical Engineering
Department: Faculties > Engineering and Environment > Mathematics, Physics and Electrical Engineering
Depositing User: Paul Burns
Date Deposited: 21 Aug 2018 10:26
Last Modified: 01 Aug 2021 07:48
URI: http://nrl.northumbria.ac.uk/id/eprint/35431

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