Fano resonance with high quality (Q) factor is of great significance to enhance the interaction between light and matter. The all-dielectric metasurface has low loss and can be used to realize the Fano resonance with high Q-factor. Herein , we propose a novel metasurface and apply it to the optical refractive index sensor in the near infrared. It consists of a silicon layer based on four rectangular holes and the substrate is silica. By introducing a new rectangular hole, the symmetry of the structure is broken and two new Fano resonance peaks are excited at the same time. The maximum Q-factor is 7709 (at 1304.4 nm). It can be applied to optical refractive index sensor with sensitivity of 296.7 nm/RIU and FOM of 1483.5.
Fano resonance with high Q-factor based on all-dielectric metasurface is of great significance for the design of optical refractive index sensor. Herein, we proposed an all-dielectric metasurface structure based on silicon, which is composed of two circular holes and one hexagonal hole. The substrate is silica. Two schemes are put forward to achieve asymmetry structure: changing the radius of a circular hole and changing the circular hole into an elliptical hole. Both schemes can generate quasi-BIC mode. The transmission spectrum is calculated by finite difference time domain (FDTD) simulation software, and the maximum Q-factor can exceed 24000. Finally, the extremely narrow linewidth of Fano resonance is utilized to design the optical refractive index sensors, yielding the sensitivity of 273nm / RIU and figure of merit (FOM) of 2730.
We designed ab all-dielectric device based on permittivity-asymmetric rectangular holes, yielding multiple Fano resonances with high Q-factor in the near-infrared regime. there is a newly-generated sharp Fano peak with arising from the interference between sub-radiant modes and the electric and magnetic dipole resonance modes. Combining the multipole decomposition based on cartesian system and the field distribution, the resonance modes are analyzed to be toroidal dipole (TD) and magnetic dipole (MD). Furthermore, the dependence on materials and geometric parameters has been studied and the maximal quality (Q)-factor reaches 28503. This structure may be used for optical switching, nonlinear optical devices, and laser
Fano resonances based on circle-with-inner-core and stub structure are investigated using data derived from the finite element method and theoretically explained by the multimode interference coupled mode theory and the electric distribution in the system. The parameters of specific structure are modified to investigate the influence of different parts for this metal–insulator–metal system. Due to the high sensitivity to filled dielectric materials, the proposed structure can be applied as a refractive index sensor, whose performances are also explored. High sensitivity is gained as high as 1183.3 nm / RIU. And the figure of merit, a key parameter to describe the sensing characteristic, is achieved as 5.1115 × 104, which is better than most similar structures. Our work is significant for the sensitive refractive index nanosensor.
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