THz Asymmetric Transmissi On Devices Based On Metamaterials

Metarmaterial is an artificial periodic structure with both the equivalent permittivity and magnetic permeability negative.In recent years,the emergence of artificial metamaterials has provided important applications for microwave and terahertz wave functional devices.In this dissertation,firstly,development of the asymmetric electromagnetic transmission device is introduced.Then,based on the transmission matrix theory,the principle of asymmetric transmission is analyzed,and the simulation process of the asymmetric transmission device is given by using simulation software CST.Finally,two kinds of wideband terahertz asymmetric transmission devices are designed.Two kinds of microwave all-dielectric asymmetric transmission devices are proposed,and a terahertz all-dielectric asymmetric transmission device is proposed.The main contents of the work include:1)Two kinds of asymmetric transmission metamaterials in terahertz bandare designed.The two structures are dual-opening rectangular ring structures and double "F" structures with relative asymmetric transmission efficiency 0.87 and 0.81,respectively.Furthermore,the principles of asymmetric transmission is deeply analyzed,and the influence of the thickness of medium and the width of metal structure on the asymmetric transmission coefficient and polarization conversion rate are studied.After that,a simple comparative analysis is made for the complementary structure of the double open rectangular ring structure.2)Two kinds of all-dielectric asymmetric transmission devices for microwave band are proposed,which are double "L" structure and right angle-rectangular bar structure,respectively.Among them,the transmission effect of the double "L" structure is good,the transmission efficiency can reach 0.93.As the right angle-rectangular bar structure has double axial symmetry,it not only can achieve the microwave asymmetric transmission line polarization wave,but also can realize asymmetric transmission of circular polarized wave.In addition,the asymmetric transmission principle of these two structures and parameter variations on the transmission are analyzed.3)An asymmetric transmission device for all-dielectric metamaterial in terahertz band is proposed.The structure is based on double "L"structure.The asymmetric transmission efficiency is 0.93.As the proposed structure is totally made up of dielectric materials,the processing cost and loss may be much lower than those of traditional metal metamaterials.The research results is of great significance for developmenting asymmetric transmission devices in the terahertz band.