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An all-dielectric hollow nanocylinder dimer metastructure with high sensitivity is proposed and investigated. The unit structure consists of two nanocylinders with two circular air holes etched into them, which are periodically aligned on the SiO2 substrate. Combined with the bound states in the continuum (BIC) theory, five Fano resonances are achieved by breaking the symmetry (height symmetry or aperture symmetry) of two hollow nanocylinders. The modulation depth can reach nearly 100%, the maximum Q-factor exceeds 2220, the refractive index sensitivity is 870 nm/RIU, and the figure of merit (FOM) of 600 is achieved. Therefore, it is believed that the suggested metastructure can be widely used in lasers, optical switches and biological sensors due to its high sensitivity and high Q-factor. [ABSTRACT FROM AUTHOR]

A novel asymmetric all-dielectric metasurface supporting multiple Fano resonances with high quality-factor through the excitation of quasi-bound states in the continuum is theoretically investigated. It is demonstrated that two resonances in the near-infrared wavelength are excited by the symmetry-protected bound state in the continuum, which can be transformed into the electric dipole and the toroidal dipole quasi-BIC resonance with high quality-factor by breaking the symmetry of metasurface. Moreover, the sensing properties based on different liquid refractive indexes are researched theoretically. The results show that the maximum quality-factor of the Fano resonance peak is 8422, and the sensitivity can reach 402 nm/RIU, with a maximum figure of merit of 2400 RIU−1. This research is believed to further promote the development of optical sensing and nonlinear optics. [ABSTRACT FROM AUTHOR]