Highly-Miniaturized Nano-Plasmonic Filters Based on Stepped Impedance Resonators with Tunable Cut-Off Wavelengths

This paper presents the design and numerical investigation of tunable, ultra-compact, and highly-efficient plasmonic filters based on stepped impedance resonators (SIRs). The proposed devices are realized in metal–insulator-metal (MIM) plasmonic waveguide systems and exhibit more degrees of freedom and high flexibility to design resonator-based devices, thanks to the SIRs. The principle of conventional SIRs is discussed in terms of equivalent circuit model and characteristic impedance. Among the three proposed plasmonic filters, one of them acts as a short-wavelength, while the other two nanostructures work as long-wavelength cut-off filters at near-infrared region (NIR) and telecom wavelengths. Simulation results are carried out by a finite element method (FEM)-based solver and indicate that the cut-off wavelengths of the proposed resonators found to be at 1187 nm, 1265 nm, and 999 nm, respectively, can be easily tuned by modulating their structural parameters. In addition to the mentioned remarkable properties of the designed structures including the size which are found to be 500 nm × 310 nm, 350 nm × 285 nm, and 210 nm × 195 nm, respectively, the simple structures of the proposed topologies facilitate their fabrication process. Therefore, the suggested devices can contribute to the development of miniaturized, tunable, and efficient optical components for photonic integrated circuits (PICs) applications and in optical wireless communication systems.