Lineshape Modulation and Sensing Characteristics of Resonator Assembled With Liquid-Metal Core Edge-Coupled With Microfiber Coupler

The resonant response of the hollow microcapillary resonator (HMCR) assembled with liquid-metal core edge-coupled with microfiber coupler (MFC) was theoretically and experimentally investigated. Primarily, for the first time, the analogy electromagnetically induced transparency (EIT) phenomenon and Fano resonance was proposed and discovered in this coupling system. Different from the traditional method, the discrepancy in temperature characteristics of waveguide super-mode and whispering gallery mode (WGM) leads to the evolution of EIT and Fano resonances. This feature has great application value for fiber optic sensors, filters, and switches due to its sharp and asymmetric lineshape. Secondly, the temperature response characteristics were improved by assembling a liquid metal core inside the HMCR. Benefitting from the high thermal expansion-coefficient material, this solution reduces externally imposed energy consumption during the tuning process. In addition to all that, to realize the multi-parameter tuning characteristics, a fiber Bragg grating (FBG) unit was constructed to perform strain tuning. This research has significant implications for sensor measurement, optical filters, optical switches, and optical modulators.