Probing the electrodynamic local density of states with magnetoelectric point scatterers

TL;DR

This paper investigates how magnetoelectric point scatterers, like split ring resonators, respond to local electromagnetic environments by analyzing their extinction spectra near interfaces, revealing the interplay of electric and magnetic LDOS.

Contribution

It introduces a method to probe the magnetoelectric cross-coupling components of polarizability tensors using extinction measurements near interfaces.

Findings

Dependence of extinction cross section on mixed magnetoelectric LDOS.

Comparison of analytical and finite element models for scatterer response.

Identification of the interplay between electric and magnetic dipole moments.

Abstract

In a scattering experiment, the induced dipole moments of a magnetoelectric point scatterer in response to driving fields are given by its polarizability tensor \alpha. Its linewidth will be dictated by the local density of optical states (LDOS) at the scatterer's position. To retrieve the magnetoelectric cross coupling components of \alpha for an archetypical magnetoelectric scatterer - a split ring resonator - we study the frequency dependent extinction cross section as a function of distance to an interface. Rather than following a purely electric or purely magnetic LDOS, we find a dependence which reflects the interplay of both dipole moments in a 'mixed' magnetoelectric LDOS. For a strongly magnetoelectric cross-coupled microwave scatterer, we compare analytical point dipole with finite element method calculations.