The Research About Passive Devices Based On Spoof Surface Plasmons

Surface plasmons(SPs) is a kind of surface electromagnetic(EM) mode formed by the interaction of free electrons and photons at the interface of metal and dielectric, and it has become one of the focus researches since it can break through the diffraction limit of light and achieve subwavelength confinement to the EM waves. At lower frequencies, such as terahertz(THz) or microwave frequencies, structured metal surfaces drilled with subwavelength holes or grooves can support spoof SPs, whose behavior is similar to that of the SPs. There are two kinds of SPs modes: spoof surface plasmon polaritons(spoof SPPs) and spoof localized surface plasmons(spoof LSPs). Both can find wide applications at far infrared, THz and microwave frequencies. Based on the characteristics of subwavelength confinement to the EM waves at lower frequencies, the miniaturization and integration of spoof plasmonic waveguides and components can be achieved. The main works in this dissertation are about the passive devices based on spoof SPs. The major studies and innovations are summarized as follows:1. A kind of planar compact four-way spoof SPPs wavelength splitter excited by coplanar waveguide(CPW) structure has been designed and it is easy to integrate with planar circuits. The band pass filter is introduced to improve bad isolations between branches at lower frequencies. The work is published on Japanese Journal of Applied Physics;2. We proposed a kind of four-way spoof SPPs wavelength splitter based on broad band slow wave system. By introducing specially designed waveguide branches with specific lengths at the locations where the EM waves are trapped, the trapped EM waves can be released and propagate along these branches. The band pass filter is introduced to improve bad isolations between branches. The work is published on Optics Express;3. The propagating characteristics of spoof SPPs waveguides with different groove shapes have been fully investigated. Based on these novel spoof SPPs waveguides, we designed the ultra-wideband filter, broadband slow wave system, band pass filter and four-way wavelength splitter with more compact structure. These works are published on Applied Optics,Optics Communications and Journal of Modern Optics, respectively;4. A corrugated ring resonator printed on a thin dielectric substrate with ground plane has been proposed, and microstrip line is used to excite spoof LSPs in the textured ring resonator which can enhance the multipolar fundamental mode and restrain high-order mode. A multi-band-pass filter and a plasmonic sensor to detect the refraction index of materials under test have been proposed and numerically demonstrated based on the proposed corrugated ring resonator. The work is published on Optics Express.