Design of a Band-Stop Filter Based on Metal–Insulator–Metal (MIM) Plasmonic Structures

Abstract

In this work, a comprehensive study of plasmonic band-pass filters based on Metal Insulator–Metal (MIM) waveguides and resonant cavities has been presented. The investigation was motivated by the growing demand for compact, highly selective, and efficient optical components suitable for modern nanophotonic and integrated optical systems. The study began with a review of the fundamental principles of plasmonics, including Surface Plasmon Polaritons (SPPs), Localized Surface Plasmon Resonances (LSPRs), plasmonic materials, nanostructures, and fabrication techniques. Particular attention was given to the mechanisms responsible for light confinement and electromagnetic field enhancement at the nanoscale. Subsequently, the main plasmonic devices and applications were examined, with a focus on plasmonic filters and their importance in optical communications, sensing technologies, and integrated photonic circuits. The operating principles, performance characteristics, and technological advantages of plasmonic filtering structures were discussed in detail. The practical part of this work focused on the design and optimization of a plasmonic band pass filter based on an MIM waveguide coupled to resonant cavities. Starting from a single cavity configuration, the structure was progressively improved through the addition of multiple resonant cavities. The effects of geometric parameters and coupling mechanisms on the transmission characteristics were systematically analyzed. The obtained results clearly demonstrate that increasing the number of resonant cavities improves the filtering performance. Enhanced electromagnetic confinement, sharper resonance peaks, improved spectral selectivity, and better transmission characteristics were achieved as the structure evolved from one cavity to four cavities. The final optimized configuration provided the most favorable performance among all investigated designs, confirming the effectiveness of the proposed approach. Overall, this work highlights the potential of multi-cavity MIM plasmonic structures for the realization of compact and high-performance optical filters. Such devices represent promising candidates for future applications in integrated photonics, optical communication systems, wavelength division multiplexing, and advanced sensing technologies.