Research on fabrication and sensing properties of fiber-coupled whispering gallery mode microsphere resonator

In this paper, a fiber-coupled whispering gallery mode (WGM) microsphere resonator was fabricated with using a simple package scheme. The resonant properties of the WGM resonator are analyzed and their responses to bulk refractive index and temperature are theoretically and experimentally investigated. Experiment results show that the bulk refractive index sensitivity is about 20.49 nm/RIU with detection limit of 4.3\times 10^{-4} RIU and very low temperature sensitivity of 7.38 pm/°C. Moreover, the WGM microsphere resonator is firstly used for acoustic intensity level sensing, and the sensitivity is about -1.9 pm/dB, which can enlarge the application field of the WGM sensor and can be used for noise monitoring to enhance environmental protection.This work was supported in part by the National Natural Science Foundation of China under Grant 61703080, Grant 61773102, and Grant 61603265 and in part by the Fundamental Research Funds for the Central Universities under Grant N160408001 and Grant N180404011. The work of Y.-N. Zhang was supported in part by the China Scholarship Council through the Visiting Scholarship under Grant 201806085010. The associate editor coordinating the review of this article and approving it for publication was Dr. Daniele Tos