Research And Application Of Spoof Surface Plasmon Polaritons Structures

As an important derivative of surface plasmon polaritons in optical frequencies, spoof surface plasmon polaritons(SSPPs) have attracted the attention of many scholars because of their excellent features in microwave and terahertz frequencies. Essentially, they are a kind of surface electromagnetic wave which is confined by grooves or holes in the metal surface and propagating along the surface. In this article, the ultrathin SSPPs structures have been studied deeply.Firstly, the ultrathin metal single grating has been discussed as a SSPPs waveguide. We find that the single grating has bigger loss when it propagates SSPPs. In order to overcome this problem, we proposed the double gratings as SSPPs waveguides. Then, we analyze the double gratings from the dispersion relations, propagation characteristics, and mode features. The results show that the depth of the grooves and the permittivity of the substrate have a great influence for the cut off frequency of SSPPs in the double gratings. It’s worth pointing out that the fundamental mode is odd SSPPs mode in the double gratings. This point is very important for us to design the exciting device. Furthermore, we proposed and studied the composite periodic grating as SSPPs waveguides. The results prove that the composite periodic grating supported the double frequencies band for SSPPs wave.Based on the electric distributions of the odd SSPPs mode, we designed two exciting device for odd SSPPs mode in double gratings: one is fed by micro-strip line; another one is fed by coplanar waveguide(CPW). The experimental results demonstrated that both the exciting devices can excite the SSPPs wave effectively in double grating. Two kinds of exciting devices have different characteristics and are used for different occasions. Combined with the double gratings and exciting devices, we fabricated four functional devices, such as, two straight SSPPs filters, a 900 bending SSPPs filter, and a dual-band SSPPs filter based on the composite periodic structure. Finally, we introduce another structure(H-structure) which is researched by predecessor. Then, a SSPPs power divider has been proposed, which based on the composite H-structure. The experimental results demonstrated that all of these functional devices have excellent features. These researches laid a certain foundation for SSPPs from theory research to practical application.