Abstract
Extinction cross-section spectra of split-ring-resonator dimers have been measured at near-infrared frequencies with a sensitive spatial modulation technique. The resonance frequency of the dimer's coupled mode as well as its extinction cross-section and its quality factor depend on the relative orientation and separation of the two split-ring resonators. The findings can be interpreted in terms of electric and magnetic dipole-dipole interaction. Numerical calculations based on a Discontinuous Galerkin Time-Domain approach are in good agreement with the experiments and support our physical interpretation.
Highlights
The metamaterial concept has enriched optics and photonics with new and fascinating aspects, e.g., magnetism at optical frequencies [1,2,3], negative index materials [4,5], transformation optics [6,7], and strong chirality [8,9,10]. These phenomena result from a dense arrangement of resonant metallic nanostructures (“photonic atoms”)
The optical properties of the photonic metamaterial are governed by the interplay of two contributions: (i) The optical response of the individual photonic atoms resulting from the direct excitation with the incident light field and (ii) the mutual electromagnetic couplings of the photonic atoms mediated by the scattered fields
We find that the dimer's resonance frequency shifts with increasing split-ring resonator (SRR) separation
Summary
The metamaterial concept has enriched optics and photonics with new and fascinating aspects, e.g., magnetism at optical frequencies [1,2,3], negative index materials [4,5], transformation optics [6,7], and strong chirality [8,9,10]. The optical properties of the photonic metamaterial are governed by the interplay of two contributions: (i) The optical response of the individual photonic atoms resulting from the direct excitation with the incident light field and (ii) the mutual electromagnetic couplings of the photonic atoms mediated by the scattered fields The latter can be decomposed into the elementary, i.e., pairwise, interactions of the photonic atoms, which depend on the relative separation and relative orientation of the two corresponding photonic atoms. Experiments on arrays of SRRs revealed an influence of the lateral period on the resonance frequency and linewidth of the fundamental magnetic mode [16] Another manifestation of interaction effects in metamaterials is the formation of magneto-inductive waves observed at microwave [17,18] and near-infrared frequencies [19,20]. The proportionality factor 1/ξ accounts for the sinusoidal modulation of the beam and depends only on the ratio of the modulation amplitude a and the beam radius r0 [29]
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