title: Experimental realization of a polarization-independent ultraviolet/visible coaxial plasmonic metamaterial.
abstract: We report the experimental realization of an optical metamaterial composed of a hexagonal array of coaxial plasmonic metal/insulator/metal waveguides that shows strong polarization-independent optical mode index dispersion in the ultraviolet/blue. The metamaterial is composed of silicon coaxes with a well-defined diameter in the range of 150-168 nm with extremely thin sidewalls (13-15 nm), embedded in a silver film, fabricated using a combination of electron beam lithography, physical vapor deposition, reactive ion etching, and focused ion beam polishing. Using a Mach-Zehnder interferometer the phase advance is measured on several metamaterial samples with different dimensions in the UV/visible part of the spectrum. For all geometries the spectral features as well as the geometry dependence of the data correspond well with numerical finite-difference time domain simulations and the calculated waveguide dispersion diagram, showing a negative mode index between 440 and 500 nm.
authors.affiliation: Center for Nanophotonics, FOM Institute AMOLF , Science Park 104, 1098 XG Amsterdam, The Netherlands.
authors.forename: M A
authors.initials: MA
authors.lastname: van de Haar
authors.forename: R
authors.initials: R
authors.lastname: Maas
authors.forename: H
authors.initials: H
authors.lastname: Schokker
authors.forename: A
authors.initials: A
authors.lastname: Polman
keywords: Plasmonics; metamaterial; nanofabrication; negative index; optical interferometry