Surface Plasmon Polariton Mediated Multiple Toroidal Resonances in 3D Folding Metamaterials

Abstract

© 2017 American Chemical Society. Toroidal dipole has attracted tremendous attentions in nuclear, particle, condensed matter and material physics due to its exotic characteristics that are distinct from the fundamental electric and magnetic dipoles. Due to the very weak intensity, toroidal dipolar response is extremely difficult to be detected in natural materials. Although single dynamic toroidal dipole has recently been observed in metamaterials, simultaneous observation of multiple toroidal dipole resonances is still very challenging, and many intriguing physical phenomena associated with them have remained elusive. Here we experimentally demonstrate an approach to achieving toroidal dipole responses with high quality factors in the infrared region via surface-plasmon-polariton excitation. Implementation of this concept leads to simultaneous experimental observation of double toroidal modes in 3D metamaterial. Periodicity and angle dependent transmission measurements clearly reveal the coupling between the surface-plasmon-polariton mode and toroidal modes. Our demonstration provides a unique platform for the study of toroidal electrodynamics and various astonishing optical phenomena involving toroidal moments.