Color-dependent unidirectional scattering of a plasmonic heterodimer investigated by a dipole-dipole interference...

In this paper, we employ an interference model of two separated electric dipoles to study the color-dependent unidirectional scattering of a plasmonic heterodimer consisting of a pair of gold and silver disks of the same size. The dipole moments in such a dipole-dipole interference model are numerically obtained by a multipole decomposition method. It shows that the power difference between the different scattering directions predicted by the dipole-dipole interference model agrees well with that calculated by the full wave simulation. The dipole-dipole interference model indicates that the scattering directionality of the heterodimer is intimately related to its geometrical parameters, including the height and radius of the disk as well as the distance between two disks. We further show that the color routing of such a heterodimer is also maintained when an electric or magnetic dipole source is positioned in the center of the heterodimer. Finally, we propose an approach to enhance bidirectional scattering by arranging the heterodimer in a line and then the main lobe beamwidth can be reduced to about 26 deg for the right scattering and 29 deg for the left scattering. Our results may be used in designing integrated plasmonic nanocircuits that demand light guiding and routing in nanoscale.