Temperature-Tunable Optical Filter Based On Fano Resonance Liquid-Core Microcapillary Resonator

In this paper, we demonstrate a novel Fano resonance optical filter based on thin fiber taper coupled whispering gallery mode (WGM) liquid core microcapillary resonator, and such the filter comes from the narrow band transmission spectrum of Fano resonance. Due to the large thermos-optical coefficient of the liquid core, slight temperature change will greatly change the resonant wavelength. In addition, high order resonant modes are generated through thin fiber taper coupling. With their large intensity fraction in the liquid core, these modes achieve high sensitivity to refractive index change or temperature change of the liquid core. So this tunable filter has very large temperature tunable coefficient of about 0.4nm/K, which is far larger than other traditional methods.