Role of Surface Geometric Patterns and Parameters in the Dispersion Relations of Spoof Surface Plasmon Polaritons at Microwave Frequency

摘要

Spoof surface plasmon polaritons (SSPPs) can be excited using geometric shapes on conducting surfaces in microwave (MW) regime. They are eminent as compared to the conventional microstrip (MS) transmission lines, due to their better efficiency and compactness in high density and high-speed circuitry. In this work, we compare normalized dispersion curves (DCs) of different groove shapes engineered on the planar metallic strip with the variation of geometric parameters of the structure, which are obtained by Eigen-mode solver of ANSYS's HFSS. It is found the dispersion characteristics are determined by the shape and the asymptotic frequency can finely be tuned through the geometric parameters. All DCs deviate further from the light line indicating slow propagation of SSPPS. The performance of rectangular grooves is clearly outstanding; however, the circular grooves behave comparably better than Vee-groove. Further, a low pass plasmonic filter has been proposed with semicircular gradient subwavelength grooves designed on a planar metallic strip with transition sections to match both the impedance and momentum of MS line and the plasmonic waveguide. Results of S-parameters and magnitude of electric field distributions show excellent transmission efficiency from fast guided wave to slow SSPPs. It is also observed that the confinement of such surface waves is dependent on the geometric parameters which can be useful in plasmonic structure engineering and fine-tuning the cutoff frequencies, hence posing a new prospect for advanced plasmonic integrated devices and circuits.