Scattering suppression and field enhancement of the fundamental plasmonic mode in bent nanorods

We study the absorption and scattering cross sections of three-dimensional retardation-based plasmonic resonators as straight gold nanorod antennas are transformed gradually to split-ring resonators. Using a multipole expansion of the scattered field, we show by bending the nanoantennas that it is possible at the fundamental resonance to suppress the scattering due to a decrease in the electric dipole response in favor of a magnetic dipole response. The decrease in scattering strength is accompanied by an increase in the Q-factor which in the split-ring resonator limit is improved by a factor of ~1.9 (equivalent to ~1.2 times larger than the quasi-static value). Additionally, the split-ring resonator shows promising prospects in surface enhanced sensing applications with local field enhancement of ≥50 in the split-ring gap. Copyright © 2011 American Scientific Publishers.