Dresden 2011 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 58: [DS] Plasmonics and Nanophotonics (jointly with HL and O)
O 58.5: Vortrag
Mittwoch, 16. März 2011, 18:15–18:30, GER 38
Periodic Nanostructures: Spatial dispersion mimics chirality — •Bruno Gompf1, Julia Braun1, Thomas Weiss1, Harald Giessen1, Martin Dressel1, and Uwe Hübner2 — 1Physikalisches Institut and Research Center SCOPE, Universität Stuttgart — 2Institut für Photonische Technologien, Jena
The underlying idea of metamaterials is that it should be possible to construct artificial materials with completely new effective dielectric properties from nanometer-sized photonic atoms. One of these new fascinating properties is, for example, the recently achieved optical activity in photonic metamaterials. In our work we demonstrate that even a simple isotropic metal-dielectric nanostructure, i.e., a sub-wavelength hole array on a square lattice in a semitransparent Au film, rotates the polarization state at oblique incidence, but this behaviour cannot be explained by effective optical parameters. The structure was characterized by Mueller matrix spectroscopic ellipsometry at various angles of incidence and azimuthal orientations in the energy range of 0.73 to 4.6 eV. For the additional theoretical simulations, we employed a Fourier modal approach. To visualize the theoretical and experimental results, we plot the matrix elements in polar coordinates. Already from a brief look at the off-diagonal elements, it becomes obvious that the hole array mixes different incoming polarization states upon reflection in a complex way, which can not be explained by purely dielectric optical constants. It can be shown that for our square array even a bi-anisotropic model must fail. Rather spatial dispersion has to be taken into account.