Electrically Controlled Optical Metamaterials Based on Dispersions of Nano-Rods
Abstract
We proposed 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 demonstrated electrically induced change in refractive index on the order of 0.1. By exploring local light absorption and birefringence, and by developing a model of light propagation in a medium with spatially varying composition, we determined the concentration of NRs and field-induced changes in the refractive indices as the function of spatial coordinates in a nonuniform electric field. We demonstrated that the electric-field induced condensation and alignment of gold NRs near the central region of a cylindrical shell causes bending of light rays around the region enclosed by the shell and to the mitigation of the shadow of the central electrode (nonideal cloaking effect). We also describe liquid crystal metamaterials (LCMMs), representing a composite of a liquid crystal (rather than an isotropic fluid) as a dispersion medium and solid (metal) NRs as a dispersed component. The purpose of the metal component is to vary the effective refractive indices and the resulting birefringence. By spatially distorting the optic axis of LCMMs and by controlling concentration of the metallic component, one can design different trajectories of light propagation through the medium as illustrated analytically and numerically for cylindrical samples of LCMMs. Depending on the refractive indices and configuration of the optic axis in LCMM, the light beam can be concentrated thus offering an approach for the solar energy storage, or bent around the obstacle.
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 15, 2011
- Accession Number
- ADA567711
Entities
People
- Andrii B. Golovin
- Heung-shik Park
- Jie Xiang
- Luana Tortora
- Oleg D. Lavrentovich
Organizations
- Kent State University