Tunable Resonances in the Plasmonic Split-Ring Resonator

A nanoscale resonator composed of two metal-insulator-metal (MIM) waveguides and a split ring is investigated numerically. The multipolar plasmonic resonance modes can be excited, weakened, or even cut off by adjusting the split angle. These novel phenomena are due to the electric polarization in the split area. Odd modes exhibit when the electric field is polarized perpendicular to the split. The resonator acts as a LC circuit for the electric field polarized parallel to the split, in which even modes are excited. The capacitance diminished when the split depth is increased, and the resonance wavelengths of even modes exhibit blue shift. Our results imply an extensive potential for tunable multichannel filters and biosensor devices in integrated nano-optics.