High Q-factor Fano resonances based on an all-dielectric metasurface for high-performance refractive index sensing

This paper proposes a high-performance refractive index sensor based on an all-dielectric metasurface consisting of four silicon arcs arranged back-to-back on a silicon dioxide substrate. A sharp Fano resonance with a high quality factor (Q-factor) in the near-infrared (NIR) wavelength is innovatively excited by electric quadrupole (EQ) resonance by varying the size of the inner angle. And electromagnetic field distribution and mode assessment further demonstrate that the EQ resonance mode is governed by quasi-bound states in the continuum (Q-BICs). Additionally, the ability to precisely control Fano resonance peaks is demonstrated by tuning the geometrical parameters of the structure, which makes the designed metasurface a promising gas refractive index sensing candidate. The results show that the highest Q-factor, sensitivity (S), and figure of merit (FOM) are 23,236, 603 nm/RIU, and 9869RIU −1 , respectively. The proposed structure provides a good application prospect for nonlinear optical devices and air refractive index sensors.