Design Of Electromagnetically Induced Transparency Metasurfaces Based On Bound States In Continuum

In recent years,analogue of Electromagnetically induced transparency(EIT)by metasurface has received extensive attention.Bound states in continuum(BIC)provide a new idea for the realization and regulation of metasurface-like EITs.However,there are few research reports on this issue in the world.This thesis focuses on BIC-based high-Q EIT metasurfaces.The main research contents are as follows:(1)A silicon cuboid BIC metasurface is studied,and the transmission spectrum and near-field electromagnetic field distribution of the metasurface are calculated by numerical simulation of electromagnetic waves.Multipole scattering power analysis shows that the metasurface supports toroidal dipole resonance.In particular,when the length of the silicon cuboid is equal to the period,the two-dimensional(2D)metasurface degenerates into a one-dimensional(1D)BIC metasurface,and eigenmode analysis shows that the metasurface supports FW BIC.(2)Based on the above-mentioned silicon cuboid BIC metasurface,a metal-dielectric hybrid bilayer EIT-like metasurface is designed and studied.The response of EIT-like is studied in two ways: coupling between low-Q electric dipole resonance and quasi-BIC toroidal dipole resonance(bright mode-bright mode)/ coupling between low-Q electric dipole resonance and ideal BIC toroidal dipole resonance(bright mode-dark mode).In particular,under the combined action of the F–P effect and the coupling between the two resonances,an EIT resonance with a Q value of up to 4022 is achieved,and the interaction distance between the two resonances is extended to nearly one operating wavelength,which is much larger than that of the traditional one-tenth of a wavelength.The thesis also calculates the refractive index sensing properties of high-Q EIT-like metasurface,which can be applied to high-sensitivity sensing.(3)A BIC-based all-dielectric bilayer EIT-like metasurface is designed and studied.The effect of the Q value of the toroidal dipole quasi-BIC resonance on the EIT-like response characteristics is studied,and the high transmittance and high Q EIT-like response is reported for the first time based on the ideal BIC.This unique 1D-2D EIT metasurface is very insensitive to the transverse relative displacement of the bilayer metasurface and has good robustness,which greatly reduces the difficulty of device fabrication and integration.