Research Of Spoof Surface Plasmons Based On Plasmonic Metamaterials

Surface plasmons(SPs)are a kind of electron dense waves excited by light on metal surface,which is a mixture of electrons and photons.The SPs are called surface plasmon polaritons(SPPs)when they are traveling in an open structure as propagating modes;and are called localized surface plasmons(LSPs)when they exist in a closed structure as local resonant modes.Due to the special property of noble metals in optical band,the theory and applications of SPs have received intensive study mainly in optical regime,where tremendous research progress has been made.In order to extend the applications to microwaves or Terahertz waves,scientists have successfully realized the so-called spoof surface plasmons(SSPs)which possess similar properties as SPs in optics,by engraving periodic grooves on metal.Similarly SSPs are called spoof surface plasmon polaritons(SSPPs)or spoof localized surface plasmons(SLSPs),depending on their existence in open or closed structures.This kind of metal engraved with periodic grooves are usually referred to as plasmonic metamaterials.Firstly,a new type of plasmonic metamaterials is designed in this thesis.The effects of geometrical dimensions of the unit cell on the dispersion curves are studied in great details.My results show that the slot depth h is the main factor affecting the dispersion relationship.The influence of the dielectric substrate on the dispersion relation of the novel plasmonic metamaterials is also analyzed.By comparing with the unit cell usually adopted in the conventional plasmonic metamaterials and the dispersion relations,we show that the novel plasmonic metamaterials designed in this paper are more effective for sustaining SSPs.Secondly,an open SSPPs waveguide structure based on the new plasmonic metamaterials is designed.A smooth matching converter between the conventional coplanar waveguide(CPW)and the new SSPPs waveguide has been proposed.By using the CPW as the feed,we have further designed four new structures of practical interests,including: a single-row SSPPs waveguide filter structure,a double-row SSPPs waveguide filter structure,a double-row dual-band SSPPs waveguide filter structure,and a SSPPs waveguide power divider.The bending loss and conformal properties of these structures are also studied.Finally,I have designed a closed SLSPs resonant structure based on the novelplasmonic metamaterials.According to the simulation results of the extinction cross section(ECS),the excitation effects of three kinds of TEM waves on the closed plasmonic metamaterials are analyzed.It is concluded that the horizontally polarized wave can excite the SLSPs resonance.In view of this conclusion,we have designed three kinds of practical excitation modes,namely,the patch monopole antenna excitation,the microstrip line excitation,and the vivaldi antenna excitation.Based on these excitations,a variety of high order SLSPs resonant modes have been excited successfully.The influences of the structure dimensions and the dielectric environment on the resonant frequencies of SLSPs are also studied.