Coaxial plasmonic metamaterials for visible light

Optical metamaterials are materials built from sub-wavelength building blocks, and can be designed to have effective optical properties that are not found in natural materials. A much-studied class of metamaterials uses small noble-metal resonant structures as building blocks, which have a magneto-electric response. These metal structures, however, suffer from high Ohmic losses near the metal plasma frequency and only work for a limited bandwidth. Furthermore, operation in the visible or UV spectral range requires scaling down of the structures to dimensions which are impossible to experimentally realize using todays available fabrication techniques. In this thesis, we consider a different approach, that circumvents these limitations, in which the effective refractive index of the metamaterial is controlled by the coupling of surface plasmon polaritons (SPPs) on thin metal-dielectric-metal (MDM) waveguides. In particular, we consider a polarization-independent geometry consisting of a hexagonal array of dielectric coaxial waveguides, embedded in metal. The dispersion of the metamaterial can be controlled by tuning the geometry of the individual coaxes and designing the coupling with neighboring coaxial waveguides. In this thesis we describe the fabrication process and determine the optical properties of such a three-dimensional coaxial plasmonic metamaterial