Research Of Terahertz Waveguide And Characteristics

Due to the development of ultrafast laser technology,the terahertz source and detector continue to develop rapidly,result that there has been increasingly great interest in terahertz wave applications.Nowadays,terahertz systems predominantly utilize free-space propagation,where has large volume and loss.Therefore,it is imperative to strengthen the study of terahertz waveguide and establish a high efficient and compact terahertz waveguide propagation system.At the same time,exploring a variety of new types of terahertz waveguide functional components will further promote the continous development and wide application of terahertz technology.We carry out study on several novel THz waveguides and functional components optimally and innovatively to solve the problem existed in free-space propagation,and improve the performance.The following four parts are included in this dissertation:(1)The basis of the selection of terahertz dielectric waveguide materials is analyzed.We firstly propose a novel kind of frequency-selective coupling for terahertz range based on solid five-core fiber.The performances of modes,losses and frequency-selective coupling have been numerically investigated by using a full vector beam propagation method.Furthermore,the effects of the variation of structural parameters on the working performances of the coupler are also investigated.The coupling principle of the frequency-selective coupler is discussed.(2)The guiding mechanism of dielectric/metal layer hollow terahertz waveguide is discussed.Based on the guiding mechanism of dielectric/metal layer hollow terahertz waveguide and the problems existed in the reported terahertz hollow waveguide directional coupler,we propose a dielectric metal layer terahertz hybrid-cladding hollow waveguide directional coupling device.In addition,by employing the finite element method,the coupling performances have been numerically investigated,including the effects of the variation of the thickness of the metal layer on the confinement losses of hybrid-cladding structures,numerical analysis of coupling characteristic,comparative analysis of confinement losses with the the existing terahertz waveguide directional coupler,and the analysis of the optimized design of the terahertz waveguide structure.Finally,the propagation mechanism of hybrid-cladding hollow terahertz waveguide is discussed.(3)The surface plasmon resonance and Fabry-Perot-like resonance is introduced.Based on it,we design a terahertz metal waveguide absorber based on pyramid-shaped groove structure.By employing the finite difference time domain method,the absorb performances have been numerically investigated,including the analysis of absorption characteristic,the analysis of the physical meaning of the absorption characteristics,the effects of incident angle,structural parameters and selection of metal material on absorption characteristics.The application of terahertz metal waveguide absorber is studied.(4)The principle of terahertz metallic wire waveguide is discussed.Based on it,we propose a design for terahertz refractive index sensing based on the multi-metal-wires and dielectric layer hybrid-cladding hollow waveguide,by employing the finite element method,the sensing performances have been numerically investigated,including comparative analysis of mode field area between the multi-metal-wires and dielectric layer hybrid-cladding hollow waveguide refractive index sensor and the metal/dielectric layer terahertz waveguide refractive index sensor,the exploratory analysis of the refractive index sensing performance,the effects of frequency and structural parameters on refractive index sensing performance,and the analysis of the optimized design of the terahertz waveguide structure.