title: On the reinterpretation of resonances in split-ring-resonators at normal incidence.
abstract: We numerically study the spectral response of 'U'-shaped split-ring-resonators at normal incidence with respect to the resonator plane. Based on the evaluation of the near-field patterns of the resonances and their geometry-dependent spectral positions, we obtain a comprehensive and consistent picture of their origin. We conclude that all resonances can be understood as plasmonic resonances of increasing order of the entire structure. In particular, for an electrical field polarized parallel to the gap the so-called LC-resonance corresponds to the fundamental plasmonic mode and, contrary to earlier interpretations, the electrical resonance is a second order plasmon mode of the entire structure. The presence of further higher order modes is discussed.
authors.forename: Carsten
authors.initials: C
authors.lastname: Rockstuhl
authors.forename: Falk
authors.initials: F
authors.lastname: Lederer
authors.forename: Christoph
authors.initials: C
authors.lastname: Etrich
authors.forename: Thomas
authors.initials: T
authors.lastname: Zentgraf
authors.forename: Jürgen
authors.initials: J
authors.lastname: Kuhl
authors.forename: Harald
authors.initials: H
authors.lastname: Giessen