All-Dielectric Metasurfaces with Toroidal Multipole Resonances at sub-THz

A novel free-standing dielectric metasurface that shows a strong toroidal resonance in the sub-THz range is proposed and demonstrated. Theoretical and experimental studies confirm the basic operation principle and electromagnetic response of the metasurface. This first demonstration of a single-layer silicon metasurface opens new venues of research for the investigation of toroidal multipoles and the engineering of ultra-high Q factor devices in the sub-THz spectral range, where high Q factors are very difficult to obtain.