Direct amplitude-phase near-field observation of higher-order anapole states

TL;DR

This paper demonstrates the experimental observation and numerical analysis of higher-order anapole states in silicon dielectric disks, revealing their strong energy confinement and narrow resonances for advanced nanophotonics applications.

Contribution

It introduces a method to identify higher-order anapole states via near-field electric measurements and confirms their properties through experiments and simulations.

Findings

Higher-order anapole states exhibit stronger energy confinement.

They have narrower resonance linewidths.

Experimental detection aligns with numerical predictions.

Abstract

Anapole states associated with the resonant suppression of electric-dipole scattering exhibit minimized extinction and maximized storage of electromagnetic energy inside a particle. Using numerical simulations, optical extinction spectroscopy and amplitude-phase near-field mapping of silicon dielectric disks, we demonstrate high-order anapole states in the near-infrared wavelength range (900-1700 nm). We develop the procedure for unambiguously identifying anapole states by monitoring the normal component of the electric near-field and experimentally detect the first two anapole states as verified by far-field extinction spectroscopy and confirmed with the numerical simulations. We demonstrate that higher order anapole states possess stronger energy concentration and narrower resonances, a remarkable feature that is advantageous for their applications in metasurfaces and nanophotonics components, such as non-linear higher-harmonic generators and nanoscale lasers.