Controlling the interplay of electric and magnetic resonances for nanoantennas
Presenter: Kan Yao
Nanoantennas are able to efficiently couple the energy of free-space radiation to a highly confined region with subwavelength dimensions and vice versa. This promises a wide spectrum of applications, such as near-field microscopy, spectroscopy and photovoltaics, etc. While the size of the optical antennas is one of the major concerns in practice, scaling down the classical microwave antennas is not sufficient for the future miniature. We propose an ultra-compact plasmonic nanoantenna with switchable directionality. The antenna comprises a metallic trimer that can support a highly spectrally tunable magnetic resonance with its amplitude comparable to that of the electric resonance. By moving one of the particles slightly for a few nanometers, the resonant frequency of the magnetic mode will shift dramatically, which leads to a change of the interference conditions and in turn the switching of the radiation direction. The enhancement of spontaneous emission and far-field radiation of a nano emitter coupled to the antenna can reach 4 and 3 orders of magnitude, respectively. Analyses based on a simple dipole model are performed and the reconstructed radiation patterns agree well with the numerical simulations.