Design of a Tunable Wide-Stopband Plasmonic Filter Based on a Metal-Insulator-Metal (MIM) Waveguide for Mid-Infrared Applications

Wide-stopband plasmonic filters are critical components for the development of compact mid-infrared (MIR) photonic systems. In this study, we propose a geometrically tunable wide-stopband plasmonic filter based on a meta-insulator-metal (MIM) waveguide integrated with dual resonator cavities. The optical response of the proposed structure is numerically investigated using the twodimensional finite-difference time-domain (2D-FDTD) method. We systematically analyze the influence of key geometric parameters, specifically the resonator height (H2) and inter-cavity distance (D), on the stopband characteristics. Our results demonstrate that the symmetric dual-cavity configuration provides effective control over both the stopband bandwidth and central wavelength. Consequently, the proposed design achieves a significantly broadened stopband while preserving structural compactness and high transmission selectivity, making it a highly promising candidate for integration into advanced MIR photonic circuits and sensing systems.