Excitation of plasmon toroidal mode at optical frequencies by angle-resolved reflection

Plasmon toroidal mode is a unique electromagnetic resonance that cannot be expanded by general electronic or magnetic multipoles. Usually, this mode excitation needs complicated nanostructures, which is a challenge for sample fabrications, especially for nanodesigns with optical resonant frequencies. In this work, we designed a circular V-groove array and studied its toroidal-mode excitation by angle-resolved reflection experimentally and numerically. Our results show that a plasmon toroidal mode around wavelength 700 nm can be excited in this simple nanostructure for incident angles larger than 20 degrees. Compared to reported papers, our design can realize the optical excitation of plasmon toroidal mode, which is useful in high-sensitivity plasmon sensors. (C) 2014 Optical Society of America