Deeper Confinement of Electromagnetic Waves Beyond Spoof Surface Plasmon Polaritons

The physics of spoof surface plasmon polaritons (SSPPs) is widely studied for their intrinsic confinement of electromagnetic wave, leading to the useful applications of device miniaturization and signal integrity. As another imitation of surface plasmon polaritons (SPPs) in microwave, effective SPPs (ESPPs) are excited inside the waveguide based on structural dispersion. Without using lossy plasmonic materials, slow wave property is achieved inside the waveguide for the interface confinement. In this work, for further enhancing the field confinement of SSPPs, the waveguide dispersion method is utilized on the structure of SSPPs. In this way, the techniques of ESPPs and SSPPs are feasibly combined for the first time, coining the name of “effective SSPPs (ESSPPs).” The dispersion relation of the ESSPPs is analyzed theoretically and numerically with the obvious field confinement. The structural dispersion makes the wavelength of ESSPPs reach 1/18 of the wavelength of SSPPs, which has potential applications for device miniaturization and signal integrity. Finally, two prototypes of the ESSPPs waveguide are fabricated on the substrate integrated waveguide (SIW) platform. The experimental results of the prototypes verify the stronger field confinement, indicating new possibilities to slow down the wave propagation with controllable confinement.