Toroidal dipole resonance under a normal incident excitation can be realized by designing a metallic circular groove with a depth asymmetry. Due to its specific radial charge current configuration, charges… Click to show full abstract
Toroidal dipole resonance under a normal incident excitation can be realized by designing a metallic circular groove with a depth asymmetry. Due to its specific radial charge current configuration, charges gather together on the central circular platform and form a plasmonic hotspot, covering a large circular region with a diameter of 200 nm, where E-field magnitude attains 34-time enhancement than that of the incident light, providing more potentials for energy harvesting or nanoparticle trapping, manipulating of light-matter interaction, and optical data storage.
               
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