Multi-conductor transmission line networks in analysis of side-coupled metal–insulator–metal plasmonic structures

An approximate and accurate enough multi-conductor transmission line model is developed for analysis of side-coupled metal–insulator–metal (MIM) waveguides. MIM waveguides have been already modeled by single conductor transmission lines. Here, the side coupling effects that exist between neighboring plasmonic structures are taken into account by finding appropriate values for distributed mutual inductance and mutual capacitance between every two neighboring conductors in the conventional single-conductor transmission line models. In this manner, multi-conductor transmission line models are introduced. Closed-form expressions are given for the transmission and reflection of miscellaneous MIM plasmonic structures, e.g. dual-stop-band and band-pass filters. In all examples, the results of the proposed model are compared against the fully numerical finite-difference time-domain (FDTD) method. The results of the analytical model are in good agreement with the numerical results.