Highly electric field enhancement induced by anapole modes coupling in the hybrid dielectric–metal nanoantenna

Abstract

Plasmonic nanoantenna has received tremendous attention in various optoelectronic applications owing to their unique optical characteristics with strong localized electric field enhancement. However, the highly intrinsic dissipation losses of metallic nanoantennas limits its application development. Coupling anapole modes of dielectric nanostructure with plasmonic mode of metallic nanoantenna seems to provide a promising alternative to further boost the electric field intensity with low dissipation losses. Herein, we demonstrate that the electric field intensity from a metallic nanoantenna can be remarkably heightened through introducing a dielectric nanostructure to build hybrid dielectric–metal nanoantenna, where the hybrid nanoantenna is composed of a gold nanorod dimer and a slotted silicon nanodisk. Through rationally optimizing the structural parameters, the hybrid nanoantenna exhibits an intensified resonant electric field intensity (> 3700 folds) at the gap of the dimer nanoantenna, which exceeds 30 times higher than that of the individual dimer nanoantenna. The far-field scattering characteristics and the near-field electromagnetic field distributions are systematically investigated to elucidate the field enhancement mechanism via utilizing numerical simulations and multipole decomposition analysis. It can be confirmed that the highly electric field intensity can be primarily attributed to the mode coupling between plasmonic resonances of Au nanoantenna and the radiationless anapole modes supported by the slotted Si nanodisk. The proposed hybrid dielectric–metal nanoantenna can serve as an effective platform to amplify the radiative decay rate and Raman scattering intensity, which paves a prospective avenue in the field of single-molecule surface enhanced spectroscopy.