The Filter Characteristic Research of Metal-Insulator-Metal Waveguide with Double Overlapping Annular Rings

A metal-insulator-metal (MIM) waveguide with double overlapping annular rings is proposed, and its transmission properties are simulated and characterized by the finite element method. The results show that the transmission valley appears in the transmission spectra when the straight MIM waveguide output port has a positional angular deviation θ relative to the incident port. Compared with the symmetric structure ( θ = 0°), the filtering properties of the asymmetric structures ( θ > 0°) are greatly improved. And compared to the MIM waveguide with single ring resonator, the filter characteristic of MIM waveguide with the double overlapping rings is superior to that of single ring resonator. For the asymmetric structure, due to the fact that parts of coupled MIM waveguide output port locates at the magnetic nodes of the standing waves in the ring resonator, there is a transmission minimum. Moreover, the asymmetric MIM waveguide can easily detect the refractive index changes of the filled media inside of resonator cavities, its potential applications in sensors.