Numerical simulation on high quality anapole resonator with large electric field concentration in all-dielectric metasurface

Abstract

In the field of nanophotonics, the manipulation of light using high refractive index dielectric materials has garnered significant attention in recent years. This occurs because dielectric materials with a high refractive index demonstrate lower losses in comparison to metallic plasmonic materials. Furthermore, the interference between internal toroidal dipole moment and electric dipole moment leads to destructive interference in the radiation field, resulting in the formation of an anapole state and localization of energy in the near-field. In this work, we initially excite the anapole state in a silicon nanodisk with a periodic nanostructured disk. By introducing a cross slit and adjusting the structural parameters, the anapole state is further optimized, and achieving highly concentrated near-field energy within the cross air slit of the silicon nanodisk. Specially designed, with a full width at halfmaximum (FWHM) of the transmitted spectrum of only 0.09 nm, and a Q factor of up to 9745, close to 104. Additionally, the structure can produce up to 571 times the electric field enhancement. The remarkable performance of a high Q factor and localized near-field energy holds great potential for various applications, including enhancing nonlinear effects, surface enhanced Raman scattering (SERS) and designing nanolasers.