Tunable ultra-narrow band band-stop filter based on metal–insulator–metal​ plasmonic waveguide with square resonator

Abstract

A tunable ultra-narrow band-stop filter based on metal–insulator–metal (MIM) plasmonic waveguide with square resonator is proposed and numerically investigated using Finite-Difference Time-Domain (FDTD) simulations. Different from straight waveguides with the same width, the proposed waveguide is composed of straight waveguides and ring waveguides with different widths. It is demonstrated that the proposed structure has a full width at half maximum (FWHM) of 9 nm at wavelength of 1261 nm. The influence of the structural parameters of the waveguides and square resonator on the transmission characteristics were analyzed in detail. The resonant wavelength can be tuned by changing the refractive index in the cavity or adding a square metal in the center of the cavity, where adding a square metal in the center of the cavity can make the resonant wavelength change proportionally. Combining the two schemes can achieve specific modulation of the resonance wavelength. Such waveguide filter may have potential applications in highly integrated optical circuits.