太赫兹金属线波导传输特性实验研究及模拟分析

Experimental study and simulation analysis of transmission characteristics of terahertz metal wire waveguides

太赫兹波介于微波与红外之间,当前太赫兹波主要在自由空间中传输,金属线波导以低损耗、低色散等突出的传输特性被广泛关注.本研究首先根据太赫兹波在不同金属线表面的趋肤深度选择铜线作为研究对象,然后基于太赫兹时域光谱系统搭建可调节式金属线波导传输特性测试光路,采集到通过不同半径、不同长度、不同端口状态的单/双铜线传输的时域信号,最后利用有限元方法对不同半径、不同形变程度的单/双根铜线在空气域的传输特性进行仿真.实验结果表明,传输损耗会随着铜线长度的增加而增加,金属线越细传输速度越慢,端口形态对传输特性的影响不如长度变化对传输特性的影响明显,双金属线越粗传输速度越快.仿真结果表明,太赫兹波在单根金属线上传输时,电场主要分布在金属线表面,金属线越细表面等离激元的模场面积越小;当金属线形变成椭圆时,模场主要分布在长轴两端;当太赫兹波在双金属线中传输时,模场主要分布在两根金属线中间,且距离越远模场面积越小.本研究结合实验与仿真分析方法对单、双金属线的太赫兹传输特性进行研究,为后续开发高效太赫兹金属波导提供参考.

Terahertz waves are between microwave and infrared,and currently,terahertz waves are mainly transmitted in free space.Metal wire waveguides have been widely studied due to their outstanding transmission characteristics such as low loss and low dispersion.In this study,copper wires are selected as the research samples based on the skin depth of terahertz waves on different metal wire surfaces.An adjustable metal wire waveguide transmission characteristic testing optical path is studied based on the terahertz time-domain spectroscopy system.The time-domain signals transmitted through single/double copper wires with different radii,lengths,and port states are collected.Then,the finite element method is used to analyze the transmission characteristics of single/double copper wires with different radii,lengths,and port states,and the transmission characteristics of single/double copper wires with different degrees of deformation in the air domain are simulated.The experimental results indicate that the transmission loss increases with copper wire length increasing,and the thinner the metal wire,the slower the transmission speed is.The influence of port shape on transmission characteristics is not so significant as that of length variation.The thicker the bimetallic wire,the faster the transmission speed is.The simulation results show that when terahertz waves are transmitted on a single metal wire,the electric field is mainly distributed on the surface of the metal wire,and the finer the metal wire,the smaller the mode field area of the surface plasmon is.When the metal line becomes elliptical,the mode field is mainly distributed on both ends of the major axis;When terahertz waves are transmitted in bimetallic wires,the mode field is mainly distributed between the two wires,and the farther the distance,the smaller the mode field area is.In this work,the terahertz transmission characteristics of single wires and bimetallic wires are studied by combining experimental method and simulation analysis,providing a reference for the subsequent development of efficient terahertz metal waveguides.