Effects of symmetry breaking on plasmon resonance in a noncoaxial nanotube and nanotube dimer

The effects of symmetry breaking on plasmonic properties of one nanotube and three types of nanotube dimers are numerically investigated. It is found that increasing the coaxial offset can result in redshifting of the transmission spectra and the existence of more peaks in the nanoegglike structures, while the nanocuplike structures present the opposite and more complex behaviors. We also study the combined effects of coaxial offset and gap size. The results show that the nanoegglike spectra redshift with the increase of coaxial offset and the decrease of the gap size, and the nanocuplike spectra display opposite behaviors. The asymmetrical distribution of surface charges demonstrates that the hybridization of dipolar and multipolar plasmon polaritons exist in the cross section of these structures, and the electric field adjacent to the thinner side enhances greatly. The proposed nanostructures may have great potential applications in various near-field optics. (C) 2011 Optical Society of America