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

Abstract

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.