Strong magnetic response of submicron Silicon particles in the infrared

TL;DR

This paper demonstrates that submicron Silicon particles exhibit strong magnetic resonances in the infrared, enabling new metamaterial applications despite low refractive index limitations.

Contribution

It reveals that Silicon nanoparticles with moderate permittivity can produce significant magnetic responses in the infrared, challenging previous assumptions about low-loss dielectric particles.

Findings

Silicon particles show magnetic resonances at 1.2-2 micrometers.

Dipolar electric and magnetic responses dominate scattering.

Higher multipole contributions are negligible.

Abstract

High-permittivity dielectric particles with resonant magnetic properties are being explored as constitutive elements of new metamaterials and devices in the microwave regime. Magnetic properties of low-loss dielectric nanoparticles in the visible or infrared are not expected due to intrinsic low refractive index of optical materials in these regimes. Here we analyze the dipolar electric and magnetic response of loss-less dielectric spheres made of moderate permittivity materials. For low material refractive index there are no sharp resonances due to strong overlapping between different multipole contributions. However, we find that Silicon particles with refractive index 3.5 and radius approx. 200nm present a dipolar and strong magnetic resonant response in telecom and near-infrared frequencies, (i.e. at wavelengths approx. 1.2-2 micrometer). Moreover, the light scattered by these Si particles can be perfectly described by dipolar electric and magnetic fields, quadrupolar and higher order contributions being negligible.