Regensburg 2013 – scientific programme
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O: Fachverband Oberflächenphysik
O 86: Plasmonics and Nanooptics VI
O 86.5: Talk
Friday, March 15, 2013, 11:30–11:45, H36
Validity of the effective medium theory for hyperbolic layered materials in the presence of surface modes. — •Maria Tschikin1, Philippe Ben-Abdallah2, and Svend-Age Biehs1 — 1Carl von Ossietzky Universität, Institute of Physics, 26111 Oldenburg, Germany — 2Laboratoire Charles Fabry, Institut d’Optique, CNRS, Université Paris- Sud, France
It is well known that the physics of periodic structures can be described by the effective medium theory (EMT) if the period of the structure is smaller than the wavelength of radiation. One example where the EMT is applied are bilayer structures with effective permittivity perpendicular є⊥ and parallel є|| to the optical axes. If both effective permittivities have different signs, i.e., є⊥є||<0, than the dispersion relation for propagating modes inside the medium is hyperbolic. In these regions the local density of states can have large values in a broad frequency band which can be used for near-field energy conversion or broadband enhanced spontaneaus emission. We consider the particular case where surface modes appear inside the hyperbolic bands and show that the EMT can lead to wrong interpretations. In particular effects which are due to surface modes could be associated to hyperbolic modes. To this end, we compare exact S-matrix calculations with the results of EMT and determine the regions where EMT can lead not only to quantitatively but also to qualitatively wrong results.