All-dielectric metastructure based on multiple Fano resonances with high sensitivity

Fano resonance with narrow linewidth through the theory of quasi-bound states in the continuum (quasi-BIC) plays an effective role in the field of optical sensors. In this paper, an all-dielectric metastructure is proposed which consists of two silicon-notched cylinders (TSNC) in the unit cell to design an optical refractive sensor with multiple and sharp Fano resonances. By breaking the symmetry, TSNC are used to excite four Fano resonances by toroidal dipole (TD), in which the maximum of Q-factor is 1320. Particularly, the sensitivity of the optical refractive sensor can reach 652 nm/RIU. It is believed that the optical refractive sensor based on the TSNC can be widely used in biomedical, agricultural and chemical sensing fields due to its high sensitivity.