Band-stop filter and narrow band-pass filter based on metal-insulator-metal waveguide

A metal-insulator-metal (MIM) waveguide comprising concave and triangular cavities is proposed, and its transmission characteristics are studied by the finite element method (FEM). The calculation results indicate that a U-shaped region with band-stop filtering characteristics is formed by the two Fano resonances. This structure achieves a sensitivity of 1400 nm/RIU, and the cascade coupling of the structures realizes narrow band-pass filtering. The simulation results indicate that a third Fano resonance appears when the structure is optimized by adding a rectangular cavity. The optimized structure is coupled in the cascade, and a double narrow band-pass filter is obtained. Because of the characteristics of this structure, it can be applied to filters and sensors.