Using the Surface Impedance Model to Analyze Plasmonic Modes of a Circular Single Wire at Terahertz and Optical Frequencies

At optical frequencies metals are penetrated by electromagnetic fields and interact with the incident waves like lossy dielectrics with negative index. Therefore, a single metallic wire can make a waveguide to convey the optical waves. This characteristic entails considering the field distributions inside the metallic single wire for correct analysis of plasmonic waves. The surface impedance technique relaxes this condition by modeling the interior fields with surface impedance. The accuracy of this method as well as its domain of validity is studied by comparing it with two other well-known techniques namely analytical solution and the method of moment (MoM). It is shown that the surface impedance model can be accurate at terahertz and infrared frequencies when the field distributions in exterior domain are desired.