Electromagnetic multipole theory for optical nanomaterials

TL;DR

This paper introduces a new method to calculate and analyze electromagnetic multipole excitations in nanostructured materials, aiding the design and understanding of optical nanomaterials.

Contribution

It presents a simple multipole decomposition approach linked to classical field expansion, revealing that different multipoles can produce identical scattering fields.

Findings

Different multipoles can generate identical scattered fields.

The method enables detailed characterization of optical nanomaterials.

It provides a basis for designing nanostructures with tailored optical properties.

Abstract

Optical properties of natural or designed materials are determined by the electromagnetic multipole moments that light can excite in the constituent particles. In this work we present an approach to calculate the multipole excitations in arbitrary arrays of nanoscatterers in a dielectric host medium. We introduce a simple and illustrative multipole decomposition of the electric currents excited in the scatterers and link this decomposition to the classical multipole expansion of the scattered field. In particular, we find that completely different multipoles can produce identical scattered fields. The presented multipole theory can be used as a basis for the design and characterization of optical nanomaterials.