Mode theory of three-layer cylindrical waveguides and its application to aurum(Au)/polystyrene(PS)-coated terahertz hollow waveguides

In this paper, we present a generic mode theory for the three-layer cylindrical waveguides consisting of three arbitrary material mediums. Based on derived eigenvalue equations of the TE, TM, and hybrid modes, the mode conditions of metal/dielectric-coated terahertz hollow waveguides are extracted. In addition, we quantitatively describe both the effective refractive indexes and the loss characteristics of the aurum/polystyrene-coated terahertz hollow waveguides operating at the TE01, TM01, and HE11 modes. It is indicated that the loss coefficient of the TE01 mode can be much lower than that of the TM01, and HE11 modes, and, especially, can tend to that of the terahertz wave in air. So the TE01 mode is very significant for the hollow waveguides in term of low loss propagating of the terahertz wave. We expect these results to enable a variety of new long-distance THz applications in sensing, detecting and communicating.