Characterization Of Novel Terahertz Guided Wave Structures

Since terahertz wave between millimeter-wave and infrared shows many advancefeatures compared with other frequency band, it has important scientific value andbroad application prospect in radar imaging, material analysis, and mass storagecommunication. As a result, terahertz technology has been one of the popular areas inscientific research recently. Terahertz transmission line is dispensable to build up thefoundation of the terahertz technology development and application. However, due tothe lack of terahertz guided waves structure with low loss and low dispersion, theapplications and integrations of terahertz systems has been greatly limited. So theresearch and development of high-performance terahertz novel guided waves structureis very important for developing a range of potential applications. The main contents ofthis dissertation are summarized as follows:1,Based on the Sommerfeld model, the terahertz propagation characteristic of thecylindrical G line and the conical G line is analyzed. The expression of energydistribution of the cylindrical G line is deduced, and the influence of different materialsand configuration parameters on the terahertz propagation characteristic of waveguide isanalyzed. The conical G line is proposed to realize the enhancement of energy focus byimproving the configuration of cylindrical G line. By using the method of numericalintegral, the energy distribution equation of waveguide is proposed. And the fielddistribution and the energy coupling capability of the conical G line are studied at0.1-1THz, by solving the complex eigenvalue equation and using the power flow theorem.The results show that the conical G line can realize the characteristic of energy focus.By solving the complex eigenvalue equation of waveguide in80-500K, the energydistribution of the conical G line is analyzed at0.1-1THz. The results show that theconical G line has good propagation characteristic at cryogenics.2,Based on the electromagnetic wave reflection between dielectrics with differentrefractive index, the dielectric tube loaded with metal wire waveguide is proposed byimproving the configuration of G line. Based on the Helmholtz equation, the basicequation of the proposed guided wave structure is deduced through field-match method.By solving the complex eigenvalue equation, the energy distribution of waveguide isobtained. The results show that the proposed guided wave structure has lowerpropagation loss, lower dispersion characteristic and greater field comfnement at terahertz frequency. The influence of various metal conductivity models on the terahertzpropagation loss is studied by theoretical calculation. The results show that the classicalrelaxation-effect model will demonstrate the surface characteristic parameters of metalat terahertz frequency more accurately.3,Based on the energy absorbing capability of dielectric material, an air-coreddielectric tube with double layers is proposed by improving the configuration of single-layer dielectric tube. The proposed guided wave structure can be used to realize higherenergy focus characteristic. Through theory modeling and solving the complexeigenvalue equation, the propagation characteristics of air-cored dielectric tube withdouble layers are studied at terahertz frequency. With the consideration of differentconfiguration parameters, the dispersion characteristic of air-cored dielectric tube withdouble layers is studied at terahertz frequency, and THz-TDS is used to measure theeffective refractive index and the ratio of power amplitude of the single-layer dielectrictube and air-cored dielectric tube with double layers. The calculated results and themeasured values show that the air-cored dielectric tube with double layers can realizehigher energy focus characteristic than the single-layer dielectric tube, and thedispersion of the proposed waveguide is weaken with the increasing of frequency.4,Based on the electromagnetic wave reflection that happens on the surface ofdielectric slab, a shielded dielectric doule-slot waveguide is proposed by improving theconfiguration of dielectric slot waveguide. The power distribution equation of shieldeddielectric multiple-slot waveguide is deduced from field match method and numericalintegration in the form of Riemann sum. The results show that the proposed guidedwave structure has good propagation characteristic at terahertz frequency. The deviationof terahertz loss among various metal conductivity models is studied by theoreticalcalculation.In conclusion, this dissertation fulfills a comprehensive analysis in the terahertzpropagation characteristics of metal wire surface wave guided wave structure, dielectrictube guided wave structure and dielectric-slab guided wave structure. The deviation ofterahertz propagation loss between various metal conductivity models is analyzed.