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Journal Article
Subwavelength Localization and Toroidal Dipole Moment of Spoof Surface Plasmon Polaritons
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- Authors
- Seong-Han Kim, Sang Soon Oh, Kap-Joong Kim, Jae-Eun Kim, Hae Yong Park, Ortwin Hess, Chul-Sik Kee
- Issue Date
- 2015-01
- Citation
- Physical Review B : Condensed Matter and Materials Physics, v.91, pp.1-9
- ISSN
- 1098-0121
- Publisher
- American Physical Society(APS)
- Language
- English
- Type
- Journal Article
- Abstract
- We experimentally and theoretically demonstrate subwavelength scale localization of spoof surface plasmon polaritons at a point defect in a two-dimensional groove metal array. An analytical expression for dispersion relation of spoof surface plasmon polaritons substantiates the existence of a band gap where a defect mode can be introduced. A waveguide coupling method allows us to excite localized spoof surface plasmon polariton modes and measure their resonance frequencies. Numerical calculations confirm that localized modes can have a very small modal volume and a high Q factor both of which are essential in enhancing light-matter interactions. Interestingly, we find that the localized spoof surface plasmon polariton has a significant toroidal dipole moment, which is responsible for the high Q factor, as well as an electric quadrupole moment. In addition, the dispersion properties of spoof surface plasmon polaritons are analyzed using a modal expansion method and numerical calculations.
- KSP Keywords
- Band gap, Coupling method, Defect mode, Dipole moment, Dispersion properties, Electric quadrupole moment, Numerical calculation, Quality-factor(Q-factor), Resonance frequency, Surface plasmon(SP), Waveguide coupling