Optical Anapole Modes of the Hybrid Ring-Disk Nanoantenna for Electric Field Enhancement

Abstract

A promising design combining low loss, high refractive index dielectric materials with metal nanoparticles, and local plasma resonance is described for ring-disk nanoantenna. A hybrid Au ring Si disk structure with chain gaps is constructed and the distributions of the electric field and near-field enhancement of the electric fields are analyzed by numerical simulation utilizing the multipole decomposition method. The electric field strength can be enhanced efficiently using metals to improve the anapole mode response of dielectric materials with large refractive indexes. Additional enhancement of the electric field is achieved by opening the chain gap to create high-intensity hot spots inside the disk. The chain comprises 14 normal octahedrons and a few tips are created by intersecting octahedrons. The electric field is greatly enhanced at the tips where there are high-intensity hot spots. The effectiveness of this structure as a refractive index sensor is assessed. The scattering cross-section (SCS) and wavelength shifts result in a maximum sensitivity of 210[Formula: see text]nm/RIU. The results validate the design concept and the hybrid structure boasting large electric field enhancement and excellent optical sensing properties have large potential in nonlinear photonics.