Research On Electromagnetic Devices Based On Spoof Surface Plasmon Polaritons

Surface Plasmon Polaritons(SPPs)is a type of surface wave that propagates locally along the interface between a conductor and a medium.The SPPs modes on metal surfaces have important application values in optical communications,molecular sensing and material sciences due to their characteristics of local field,field enhancement and subwavelength at optical frequency band.Since professor Pendry published a paper in the famous journal "Science" in 2004 to prove the phenomenon of surface plasmon polaritons(Spoof SPPs or SPPs-like),the relevant researches had attracted widespread attentions in the scientific community,opening the door to the application of SPPs at terahertz and microwave band.Spoof SPPs is a kind of surface wave propagating confined by the geometric shape of the conductor surface.Its dispersion relationship is mainly controlled by the parameters of the conductor surface topological structure,which enhances the flexibility of the design.In recent years,with the advancement of wireless communication to terahertz and microwave bands,higher requirements have emerged for the development of new electromagnetic functional devices.Based on the theory of spoof SPPs transmission lines,this paper proposed four EM functional devices,including transmission line sensor,focusing device,WGM resonator and filter,analyzed the implementation methods of their equivalent circuit,and manufactured the prototypes for testing.Results show that spoof SPPs EM devices have a wide application prospects in wireless communication,biomedicine and sensing fields due to their flexible freedom in design.To sum up,the main research contents and innovations of the thesis include the following four aspects:1.A microwave sensor based on spoof SPPs transmission line is proposed.For the spoof SPPs transmission line composed of sub-wavelength periodic grooved arrays,the dispersion relationship and mode distribution are studied,and the influence of geometric strcture parameters on transmission responses is analyzed.Two types of spoof SPPs sensor optimized structures are proposed.A spoof SPPs sensor is manufactured,and the sensing performance is tested at the microwave band.2.The field intensity of surface wave is compressed and expanded by using the spoof SPPs gradient transmission line.Taking single-cone and bi-cone focusers as examples,the field compression ratio and transmission efficiency are analyzed,and three types of optimal focusers structures are obtained.The results show that the bi-cone has the best focusing performance and the single cone has the best transmission performance.The structure of single cone focuser with slot at the tip can enhance the focusing property.3.The spoof SPPs transmission line is connected end to end to form a closed loop,and the whispering gallery mode(WGM)is realized.For the spoof SPPs WGM resonator,the equivalent circuit implementation method of the LC transmission line is proposed and analyzed from the perspectives of field and circuit.The characteristics of WGM mode excited by microstrip and spoof SPPS transmission lines are studied,and an optimized structure of WGM discs with two different inner diameters is proposed.At the same time,the prototype of WGM resonator is manufactured,and the sensing performance is tested at the microwave band.4.The equivalent circuit model of spoof SPPs transmission line is established,and four types of metamaterial filters are designed.By analyzing the metamaterial properties of the equivalent circuit,the element values for unit circuits of RH,LH,CRLH and D-CRLH are numerically calculated.Based on the analyses,four types metamaterial filters of low-pass,high-pass,band-pass and band-reject are designed,and the D-CRLH notch filter is fabricated and tested.Compared with Butterworth filter,the metamaterial filter has the advantages of shorter group delay and continuous smooth phase changes in the rejected band.