Analysis Of The Propagating Modes In The Waveguide Of Spoof Surface Plasmon Polaritons

Surface plasmon polaritons(SPP),originating from the collective oscillation of electrons in metal,can propagate along the metal/dielectric interface.The spoof surface plasmon polaritons is the extension of the surface plasmon polaritons of light wave in the microwave and THz bands.Due to the subwavelength nature and remarkable enhancement of local fields,spoof SPP are widely extensively studied by researchers.In this thesis,the surface plasmon polaritons modes in the Metal-Insulator-Metal(MIM)waveguide structure and the Spoof-Insulator-Spoof(SIS)waveguide structure are studied systematically.Firstly,we investigate the properties of surface plasmon polariton(SPP)supported by the Metal-Insulator-Metal(MIM)waveguides.Based on the FEM simulation by software COMSOL Multiphysics,two electromagnetic modes are found,namely,symmetric mode and anti-symmetric mode.According to the field distributions,it is found that the foundmental mode is anti-symmetric mode,and the corresponding dispersion curves is obtained,which depends on the insulator width and thickness of MIM waveguide.Finally,the comparison of dispersion curves between 3D MIM and 2D MIM are shown.At low frequencies,a cut-off frequency for the dispersion curve of SPP in the 2D MIM waveguide is revealed,while the anti-symmetric mode still exists.Then,we analyze the optical properties of the spoof surface plasmon in SIS waveguide structures.Firstly,we obtain two EM modes supported in the SIS waveguide by numerical simulations and experiments,i.e.the symmetric mode and anti-symmetric mode.And we obtain the field distributions of these two modes and their dispersion curves.Next,the impact of the metal strips thickness and the changes of insulator width to the dispersion curves are analyzed.We give explanations to similarities and differences of the spoof SPP between 2D and 3D SIS waveguide from the underlying physics.And comparison to the SPP in the MIM waveguide structure are made.Finally,we study the case when the thin metal layer inserted to the insulator layer in the SIS waveguide structure.Based on the numerical simulation,the dispersion relation of the spoof SPP,the width of the thin metal layer and its position are investigated.An interpretation is given based on to the field distributions.