Publication # 359

359.        Sukru Ekin Kocabas, Georgios Veronis, David A. B. Miller, and Shanhui Fan, "Transmission Line and Equivalent Circuit Models for Plasmonic Waveguide Components," IEEE J. Selected Topics in Quantum Electronics, Special Issue on Surface Plasmon Photonics and Plasmonics, 14 (6), 1462‑1472 (Dec 2008). Digital Object Identifier: 10.1109/JSTQE.2008.924431.

Modeling of waveguide junctions using transmission lines and lumped circuit elements is common practice in microwave networks. By the help of the scattering matrix formalism, it is possible to describe junction effects in a very concise way. Such a representation is crucial for the design of complex systems containing many interacting parts. Using scattering matrices, we characterize symmetric junctions between two dimensional metal-insulator-metal (MIM) waveguides with optical signals at infrared frequencies (1550nm) propagating in them. We verify our characterization by perfectly matching a wavelength-sized MIM waveguide to a sub-wavelength sized one using a Smith chart. We then map the scattering matrix description to an equivalent lumped circuit representation and discuss the physical significance of its elements. We show that a simplified characteristic impedance model is appropriate for the deep sub-wavelength regime. The scattering matrix model for the MIM junctions leads to simplified analysis that then can be integrated into circuit modeling software packages, such as, SPICE.

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