Applications Of Non-Metallic Conducting Materials In Surface Plasmon Polaritons And Artificial Electromagnetic Structures

Surface Plasmon Polaritons(SPPs)are resonance modes formed by free-charge oscillations and electromagnetic fields that propagate on the surface of a conductor.The interaction between surface charge oscillation and the electromagnetic field renders many unique properties to SPPs,especially the important characteristics of adjusting the distribution of electromagnetic field in sub-wavelength scale,which has many unique applications.Nowadays,a mature research area named "plasmonics" has been developed.However,most of the studies on surface plasmon polaritons are limited to metallic materials,and partly because of this reason,most of them focus on the visible light and infrared wavebands.J.B.Pendry et al.proposed the artificial plasmonic materials that can manipulate the electromagnetic wave propagation at low frequencies in the way similar to that of the SPPs,known as spoof SPPs.It provides important technical means for developing surface wave integrated circuits and devices.At the same time,more and more attention has been attracted to the research of non-metallic plasmon materials.This dissertation focuses on non-metallic material surface plasmon polaritons and their applications in different wavebands,including deep ultraviolet,microwave and terahertz.The main research work and results of the dissertation are summarized as follows:1.Surface plasmon polaritons excitation based on gallium arsenide(GaAs)in deep ultraviolet band and its applications in beam enhancement.Based on the physical model of the excitation of the SPPs,it is predicted that gallium arsenide can excite SPPs in the ultraviolet frequency band.Software simulation proved that gallium arsenide can excite the SPPs under some certain conditions in the ultraviolet band,and has a better surface plasmon effect than common SPP materials such as silver Also,the designed concentric ring structure(bull's eye structure)can achieve beam enhancement in the ultraviolet band,and can get a 19 times enhancement of light intensity,while focusing the beam's half-height width(FWHM)from 48°to 6°.This work provides a new material and method for the design of the surface plasmon structure in the ultraviolet band.2.Artificial electromagnetic structure based on indium tin oxide glass in microwave band and its application in transparent ultra wideband microwave absorber.Most microwave devices use conventional printed circuit boards(PCB).We proposed a novel way of designing microwave devices using indium tin oxide(ITO)glass based on artificial electromagnetic structure.A visible light transparent microwave ultra-wideband microwave absorber based on ITO glass was designed.The transmittance of the structure in the visible light band is higher than 80%,so the absorber is transparent;at the same time,the bandwidth of the structure with absorption larger than 80%is 23.4 GHz(from 15.6 GHz to 39 GHz,and the electromagnetic wave is incident perpendicular to the surface of the structure).The experimental results verified the simulation results and the theoretical analysis.The thickness of the structure was 1.1 mm,only 0.11 times of the corresponding wavelength(9.23 mm)of the central frequency 32.5 GHz,and is possible to reduce further.Simulations also show that the absorber is insensitive to the polarization angle of incident wave.This new type of absorber is designed to realize ultra wideband and low reflection on both visible light and microwave bands It provides a new idea for the design of microwave system in the future.It is of great significance for the design of microwave stealth system and so on.3.Artificial electromagnetic structure based on indium tin oxide PET in microwave band and its application in flexible transparent ultrabroadband microwave absorber.The traditional metamaterial absorber has limitations including optical opacity,high hardness and rigidity.Especially in recent years,with the rapid development of transparent electronic devices and flexible electronic devices,the demand for flexible transparent absorber has become more and more urgent.A new type of flexible transparent microwave absorber is proposed in this dissertation,using polybutylene terephthalate(Polyethylene Terephthalate,PET)film as substrate material,ITO as conductive material,to excite surface plasmon wave.It not only maintains the characteristics of optical transparency and flexibility,but also achieves broadband absorption.The bandwidth of the absorption larger than 80%is 19.9 GHz-51.8 GHz.Experimental measurements proved the simulation and theoretical analysis results.The sample was conformed to the surface of cylinders with different diameters,and the absorption was excellent under bending condition.The absorption performance under bending condition was theoretically deduced and tested,which complied with each other.The flexible transparent absorbing structure provides a new tool for the future development and application of transparent electronic devices and flexible electronic devices.4.Surface plasmon polaritons excitation based on indium tin oxide film in terahertz band and its applications in precise location and scale bar of terahertz imaging.The use of terahertz time-domain spectrometers for imaging has become a hot spot in recent years,because of its wide spectral bandwidth,non-contact measurement,and non-destructive to the imaging target.However,the location resolution of the imaging is limited by the diffraction limit.This dissertation studies the surface plasmon polariton effect of indium tin oxide and other materials in the terahertz band,proposes a precise location structure in the reflective terahertz imaging process,and can provide an ultra-precision scale bar in reflective terahertz imaging.