Tunable Multiple Fano Resonances and Stable Plasmonic Band-Stop Filter Based on a Metal-Insulator-Metal Waveguide

Abstract

A metal-insulator-metal (MIM) waveguide consisting of two stub resonators and a ring resonator is proposed, which can be used as refractive index sensor and stop-band filter at the same time. The transmission characteristics of the MIM waveguide structure is studied by the finite element method (FEM). The simulation results show that the typical Fano profile and multiple Fano resonances can be achieved. According to the analysis, the range of stop-band and the multiple Fano resonance positions can be adjusted flexibly and independently by adjusting the aggregate parameters of the MIM waveguide structure. Moreover, it is also found that the two Fano resonances at both ends of the stop band can be determined by the two stubs, and the other two Fano resonances are regulated by the ring resonator. In addition, the spectral position of multi-Fano resonances is highly sensitive to the radius of the ring resonator and the refractive index of the filled medium. The maximum sensitivity and the figure of merit (FOM) of the MIM waveguide structure are 1650 nm/RIU and 117.8 in magnitude, respectively. These results provide a reference for implementing high-sensitivity sensors and large-bandwidth stop-band filter in MIM waveguide coupling systems based on multi-Fano resonance effect.