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1.3 PHYSICAL SCIENCES, 2.2 ELECTRICAL, ELECTRONIC, INFORMATION ENGINEERING
A new type of fiber optic sensor for detection and quantification of ammonia (NH3) vapors 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 constant relative humidity (50% RH) and constant temperature (230 C). The response and recovery times are measured as 100 and 570 seconds respectively.
Arun Kumar Mallik, Gerald Farrell, Dejun Liu, Vishnu Kavungal, Qiang Wu, and Yuliya Semenova "Porous silica coated spherical microresonator for vapor phase sensing of ammonia at a sub-ppm level", Proc. SPIE 9916, Sixth European Workshop on Optical Fibre Sensors, 99161Y (30 May 2016); DOI: 10.1117/12.2236486