Type

Journal Article

Authors

Qiang wu
Dejun Liu
Vishnu Kavungal
Manjusha Ramakrishnan
Gerald Farrell
Arun Mallik

Subjects

Physics

Topics
molecules microspheres optical properties sol gels silica physical sciences and mathematics plastic coatings temperature distribution ammonia

Whispering Gallery Mode Micro Resonators for Multi-Parameter Applications (2018)

Abstract 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, the NH3 concentration in air and the 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.
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Full list of authors on original publication

Qiang wu, Dejun Liu, Vishnu Kavungal, Manjusha Ramakrishnan, Gerald Farrell, Arun Mallik

Experts in our system

1
Qiang wu
TU Dublin
Total Publications: 90
 
2
Dejun Liu
TU Dublin
Total Publications: 24
 
3
Vishnu Kavungal
TU Dublin
Total Publications: 11
 
4
Manjusha Ramakrishnan
TU Dublin
Total Publications: 10
 
5
Gerald Farrell
TU Dublin
Total Publications: 212
 
6
Arun Mallik
TU Dublin
Total Publications: 26