Abstract

In this paper, we investigate both theoretically and experimentally the influence of the agarose hydrogel layer thickness on the sensitivity of a proposed relative humidity (RH) sensor based on a silica microsphere resonator coated with agarose hydrogel. The operating principle of the sensor relies on excitation of whispering gallery modes (WGMs) in the coated silica microsphere using the evanescent field of a tapered fiber. A change in the ambient relative humidity is detected by measuring the wavelength shift of the WGMs in the transmission spectrum of the tapered fiber. Using perturbation theory, we analyze the influence of the agarose coating thickness on the sensitivity of the proposed sensor and compare the results of this analysis with experimental findings for different coating layer thicknesses. We demonstrate that an increase in the coating layer thickness initially leads to an increase in the sensitivity to RH and reaches saturation at higher values of the agarose layer thickness. The results of the study are useful for the design and optimization of microsphere sensor parameters to meet a performance specification.

© 2017 Optical Society of America

Agarose coated spherical micro resonator for humidity measurements

Arun Kumar Mallik, Dejun Liu, Vishnu Kavungal, Qiang Wu, Gerald Farrell, and Yuliya Semenova
Opt. Express 24(19) 21216-21227 (2016)

Whispering gallery mode micro resonators for multi-parameter sensing applications

Arun Kumar Mallik, Gerald Farrell, Manjusha Ramakrishnan, Vishnu Kavungal, Dejun Liu, Qiang Wu, and Yuliya Semenova
Opt. Express 26(24) 31829-31838 (2018)

Effect of coating thickness on the sensitivity of a humidity sensor based on an Agarose coated photonic crystal fiber interferometer

Jinesh Mathew, Yuliya Semenova, and Gerald Farrell
Opt. Express 21(5) 6313-6320 (2013)

Experimental demonstration of a high-sensitivity humidity sensor based on an Agarose-coated transmission-type photonic crystal fiber interferometer

Jinesh Mathew, Yuliya Semenova, and Gerald Farrell
Appl. Opt. 52(16) 3884-3890 (2013)

Ultrasensitive chemical sensors based on whispering gallery modes in a microsphere coated with zeolite

Nai Lin, Lan Jiang, Sumei Wang, Lei Yuan, Hai Xiao, Yongfeng Lu, and Hailung Tsai
Appl. Opt. 49(33) 6463-6471 (2010)