@inproceedings{bb3e2b437015404a9185a5df2ae493d4,
title = "Porous silica coated spherical microresonator for vapor phase sensing of ammonia at a sub-ppm level",
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.",
keywords = "Ammonia sensor, Fiber optic sensor, Optical resonator, Whispering gallery mode",
author = "Mallik, \{Arun K.\} and Gerald Farrell and Dejun Liu and Vishnu Kavungal and Qiang Wu and Yuliya Semenova",
note = "Publisher Copyright: {\textcopyright} 2016 SPIE.; 6th European Workshop on Optical Fibre Sensors ; Conference date: 31-05-2016 Through 03-06-2016",
year = "2016",
doi = "10.1117/12.2236486",
language = "English",
series = "Proceedings of SPIE - The International Society for Optical Engineering",
publisher = "SPIE",
editor = "Elfed Lewis",
booktitle = "Sixth European Workshop on Optical Fibre Sensors",
address = "United States",
}