Abstract

The Laguerre-Gaussian (LG) beam, called as optical vortex, that possesses helical wave-front and doughnut beam profile has recently attracted significant attention because of the unique characteristics of carrying the orbital angular momentum in addition to the spin angular momentum corresponding to circular polarization. Recently, we demonstrated that multipolar plasmons of metal nano-disks can be selectively excited by circularly-polarized optical vortex beams [1]. The orbital and spin angular momenta are transferred from LG-mode photons to localized plasmons. This plasmonic field localized by the nano-disk just corresponds to the whispering gallery mode (WGM), where the angular mode number is determined by the total angular momentum of the LG beam. Unfortunately, the mode volume of this plasmonic resonator is sub-micrometer dimension that is restricted by the diffraction limit of the surface plasmon wave.

© 2016 Japan Society of Applied Physics, Optical Society of America