Excitation of multiple Fano resonances on all-dielectric nanoparticle arrays.

In this paper, an all-dielectric metasurface consisting of a unit cell containing a nanocube array and organized periodically on a silicon dioxide substrate is designed and analyzed. By introducing asymmetric parameters that can excite the quasi-bound states in the continuum, three Fano resonances with high Q-factor and high modulation depth may be produced in the near-infrared range. Three Fano resonance peaks are excited by magnetic dipole and toroidal dipole, respectively, in conjunction with the distributive features of electromagnetism. The simulation results indicate that the discussed structure can be utilized as a refractive index sensor with a sensitivity of around 434 nm/RIU, a maximum Q factor of 3327, and a modulation depth equal to 100%. The proposed structure has been designed and experimentally investigated, and its maximum sensitivity is 227 nm/RIU. At the same time, the modulation depth of the resonance peak at λ = 1185.81 nm is nearly 100% when the polarization angle of the incident light is 0 °. Therefore, the suggested metasurface has applications in optical switches, nonlinear optics, and biological sensors.

Multiple Fano resonances on the metastructure of all-dielectric nanopore arrays excited by breaking two-different-dimensional symmetries.

We have designed and analyzed the high quality-factor (Q-factor), multiple Fano resonances device on the basis of the all-dielectric metastructure. The unit structure consists of two rectangular air holes etched within a silicon cube and periodically aligns on the substrate of silicon dioxide. The results demonstrate that four Fano resonances are achieved by integrating the theory of bound states in the continuum (BIC)and breaking the symmetry (width symmetry or depth symmetry) of two rectangle air holes, and the resonant wavelength can be modified by altering structural parameters. The sensing characteristics of the presented structure are studied. The sensitivity(S) of 304 nm/RIU, the maximal Q-factor of 2142 and the figure of merit (FOM) of 515.3 are achieved while width symmetry is broken. Meanwhile, the sensitivity of 280 nm/RIU, the maximal Q-factor of 2517 and the FOM of 560 are gotted through breaking depth symmetry. The proposed metastructures can be used for the lasers, biosensing and nonlinear optics.