Porous silica coated spherical microresonator for vapor phase sensing of ammonia at a sub-ppm level

Lewis, Elfed, Mallik, Arun, Farrell, Gerald, Liu, Dejun, Kavungal, Vishnu, Wu, Qiang and Semenova, Yuliya (2016) Porous silica coated spherical microresonator for vapor phase sensing of ammonia at a sub-ppm level. Proceedings of SPIE - The International Society for Optical Engineering, 9916. 99161Y. ISSN 0277-786X

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Official URL: http://dx.doi.org/10.1117/12.2236486

Abstract

A new type of fiber optic sensor for the detection and quantification of ammonia (NH3) vapor levels is proposed and experimentally demonstrated. This sensor is based on a spherical silica micro resonator coated with porous silica gel. Whispering gallery modes (WGMs) in the micro resonator are excited by evanescent coupling to a tapered fiber with a 3.3 μm waist diameter. The optical properties of the porous silica layer change when it is exposed to ammonia vapor, leading to a spectral shift of the WGM resonant wavelengths. The sensitivity of the proposed sensor has been tested by exposing it to different low level concentrations of ammonia: 4 ppm, 8 ppm, 12 ppm and 30 ppm at a constant relative humidity (50% RH) and constant temperature (23°C). The detection limit is calculated from experimental results as 57 ppb of ammonia for a 282 μm diameter porous silica coated microsphere.

Item Type: Article
Uncontrolled Keywords: Microresonators; Silica; Sensors; Optical properties; Fiber optics sensors; Humidity
Subjects: F200 Materials Science
Department: Faculties > Engineering and Environment > Physics and Electrical Engineering
Depositing User: Becky Skoyles
Date Deposited: 15 Jul 2016 09:26
Last Modified: 02 Feb 2017 11:38
URI: http://nrl.northumbria.ac.uk/id/eprint/27282

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