Optical properties of plasmonic dimer, trimer, tetramer and pentamer assemblies of gold nanoboxes

The scattering and absorption properties of the monomer (single), dimer (double), trimer (triple), tetramer (quadruple), and pentamer (quintupling) assemblies with gold nanoboxes as building blocks are studied theoretically. Using the finite element method, the far-field and near-field optical responses of 1-D and 2-D assemblies are analyzed numerically to identify the plasmon modes. Our results illustrate that the longitudinal plasmon modes of 1-D array are red-shifted and more higher-order modes appear as the number of nanoboxes increases. Moreover, the 2-D assemblies show their versatile multiple modes. For example, five configurations of the tetramer (tetris structure) exhibit different plasmon modes as illuminated by different-polarized plane waves. Due to the symmetry breaking of the 2-D assemblies, the Fano resonances and dips are observed. These phenomena demonstrate that the plasmon modes of a nanobox-cluster assembly are tunable to manipulate light on demand by tailoring the configuration.