Magnetic Octupole Response of Dielectric Oligomers

TL;DR

This paper demonstrates how dividing a silicon block into an oligomer structure with nanogaps induces a magnetic octupole response, enabling tunable magnetic hot-spots and enhanced light absorption for nanophotonic applications.

Contribution

It introduces a novel method to generate and control magnetic octupole resonances in dielectric nanostructures using oligomer configurations with nanogaps.

Findings

Magnetic octupole resonance can be achieved in dielectric oligomers.

Tuning the spectral position of the resonance by adjusting nanogap distances.

Enhanced light absorption at the resonance in silicon structures.

Abstract

The development of new approaches to tuning the resonant magnetic response of simple all-dielectric nanostructures is very important in modern nanophotonics. Here we show that a resonant magnetic octupole (MOCT) response can be obtained by dividing a solid rectangular silicon block to an oligomer structure with the introduction of narrow gaps between four nanocubes. We control and tune the spectral position of the MOCT resonance by varying the distance between the nanocubes. We demonstrate that several magnetic hot-spots related to the MOCT resonance can be located in the gaps creating a strong magnetic field gradient in free space. We observe that the resonant excitation of the MOCT moment leads to a significant enhancement of light absorption in the system at the spectral region, where light absorption in bulk silicon is weak. The results of this work can be applied to design new composite antennas and metamaterials based on complex building blocks, energy harvesting devices and molecular trapping with magnetic hot-spots.