Electro-Optic Effects in Colloidal Dispersion of Metal Nano-Rods in Dielectric Fluid

TL;DR

This paper presents a method to create tunable metamaterials using colloidal dispersions of metal nano-rods in dielectric fluids, enabling spatial control of optical properties for transformation optics applications.

Contribution

It introduces a novel approach to fabricate switchable metamaterials by controlling nano-rod orientation and concentration with electric fields in colloidal dispersions.

Findings

Electric fields induce a refractive index change of about 0.1.

Spatially varying configurations of nano-rods can be achieved.

The method enables dynamic control of optical properties.

Abstract

In modern transformation optics, one explores metamaterials with properties that vary from point to point in space and time, suitable for applications in devices such as an "optical invisibility cloak" and an "optical black hole". We propose an approach to construct spatially varying and switchable metamaterials that are based on colloidal dispersions of metal nano-rods (NRs) in dielectric fluids, in which dielectrophoretic forces, originating in the electric field gradients, create spatially varying configurations of aligned NRs. The electric field controls orientation and concentration of NRs and thus modulates the optical properties of the medium. Using gold (Au) NRs dispersed in toluene, we demonstrate electrically induced change in refractive index on the order of 0.1.