Subwavelength Localization and Toroidal Dipole Moment of Spoof Surface Plasmon Polaritons

Chul-Sik Kee Integrated Optics Laboratory, Advanced Photonics Research Institute, GIST, Gwangju, South Korea Seung-Han Kim Integrated Optics Laboratory, Advanced Photonics Research Institute, GIST, Gwangju, South Korea Sang-Soon Oh Blackett Laboratory, Department of physics, Imperial College London, London, UK Kap-Joong Kim Basic Science Laboratory, ETRI, Daejeon, South Korea Jea-Eun Kim Department of Physics, KAIST, Daejeon, South Korea Hae Yong Park Department of Physics, KAIST, Daejeon, South Korea Ortwin Hess Blackett Laboratory, Department of physics, Imperial College London, London, UK

Subwavelength scale localization of spoof surface plasmon polaritons at a point defect in a two-dimensional groove metal array to exhibit a band gap where a defect mode can be introduced is demonstrated in experiments and numerical simulations. To excite localized spoof surface plasmon polariton modes and measure their resonance frequencies, a waveguide coupling method was employed. Experimental and numerical simulation results 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, 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.

cskee@gist.ac.kr









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