Research On New Terahertz Hollow Core Waveguides

ABSTRACT:The terahertz region occupies a large portion of the electromagnetic spectrum located between the microwave and optical frequencies and is normally defined as the band from0.1to10THz.In recent years,this intermediate THz radiation band has comprehensive applications,such as in sensing,in imaging,in spectroscopy,in security check,and in communication.With the development of THz sources and receivers,effective transmission of THz wave become more and more important in a THz system. Reported transmission for terahertz waveguide loss is generally greater than ldB/m, not suitable for long distance transmission. Therefore, studying a lower loss, long-distance transmission terahertz waveguide has a very important significance.This paper mainly introduced transmission characteristics of terahertz metallic hollow waveguide and dielectric/metallic waveguide and analyzed the impact of various factors of the waveguide transmission characteristics. Then through improving waveguide material and structure,proposed teflon waveguide and grapheme/teflon waveguide and analyzed systematicly the factors that can impact the mode loss in two waveguides.Firstly, we analyzed the transmission mechanism of THz metallic hollow waveguide and obtained the major mode loss curve graph with the variation of parameters. There are many modes can exist in metallic hollow waveguide,TE01mode,TE11mode,TM01mode and TE21mode are the most low order modes.TE01mode has lower loss than TE11mode,but TE11mode is suitable for transmission.Secondly, we introduced finite element numerical analysis method and Comsol simulation software. Using Comsol software,we can accurately obtain mode field distribution and transmission loss of terahertz hollow metal waveguide. Compared with the theoretical values, the error is very low.Then we studyed the terahertz dielectric/metal waveguide structure and the transmission characteristics,discussed the major modes in this waveguide.Analyzed the impacts of waveguide core diameter, type of dielectric layer, the dielectric layer thickness, metal thickness, transmission wavelength on the transmission characteristics.HE11mode is the fundamental mode and has the lowest loss in this waveguide. Through the analysis results,we could acquire the optimum waveguide structure parameters and the best material choice. Finally,the paper propose teflon waveguide and grapheme/Teflon waveguide which have simple structure waveguide.We analyse the two waveguides through finite element method using Comsol multiphysics.When the frequency is0.5THz,the fundamental mode(HE11) loss is0.398dB/m in teflon waveguide which radius is4mm and teflon thickness is0.5mm.In grapheme/teflon waveguide,when the radius is4mm,the teflon thickness is0.5mm,the bias voltage is10V,the TE01mode loss is0.58dB/m,the HE11mode loss is0.6215dB/m.