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MM: Fachverband Metall- und Materialphysik
MM 46: Nanostructured Materials III
MM 46.5: Vortrag
Donnerstag, 25. März 2010, 11:15–11:30, H16
Experimental demonstration of hyperbolic wave vector surfaces in silver nanowire arrays — •Jörg Schilling1 and Jyotirmayee Kanungo2 — 1ZIK "SiLi-nano", Martin-Luther-Universität Halle-Wittenberg, Halle — 2Queen's University Belfast, Belfast, UK
Arrays of metal nanowires represent uniaxial metamaterials, whose principal effective permittivities perpendicular and parallel to the wire axis have opposite sign in the infrared and visible spectral range. This property leads to a hyperbolic equi-frequency surface for the extraordinary rays in wave vector space allowing the propagation of waves with unusally large wave vectors. Here we present an experimental mapping of the hyperbolic equi-frequency surfaces of TM (p-) polarised light propagating within a silver nanowire array. To this purpose we performed angular resolved transmission measurements on a 1.7micron high alumina film containing the silver nanowire array. From the order of the observed Fabry-Perot resonances the wave vector component kz is determined, while the lateral wave vector component kx, is obtained from the angle of incidence. The resulting markings in kx-kz wave vector diagram then result in a hyperbolic equi-frequency surface for the TM polarisation. Fitting the relationship between spectral position of the Fabry-Perot peaks and angle of incidence by a simple linear equation, we furthermore determined the values of the principal permittivities for TE and TM polarisation in a wide spectral range. All experimental results agree well with simulations based on the Maxwell-Garnett effective medium theory.