Plasmonic Waveguide Filters Based on Tunneling and Cavity Effects

This work presents a bandstop plasmonic filter that comprises a metal-insulator-metal (MIM) waveguide and a few pairs of strip cavities that are embedded in the metal. The strip cavity acts as both a near-field antenna and an MIM resonator. The central frequency and the bandwidth of the forbidden band are inversely related to the cavity length and the cavity-to-waveguide distance, respectively. These results correlate with the predictions of the ring resonator model but only under the resonant condition that double the effective length of cavity is an integer multiple of the guiding wavelength in the cavity.