Propagation of Single-Mode and Multi-Mode TerahertzRadiation Through a Parallel-Plate Waveguide

摘要

We investigated the propagation of single- and multi-mode terahertz (THz) radiation through aparallel-plate waveguide for various gap sizes of the plates and polarizations of the incoming THzfield. Single TEM (TM_0) and TE_1 modes within the 4-THz frequency range propagated through awaveguide with a plate separation of 103 pm. Multi TE and TM modes were observed for a 360-pmseparation. High-order modes have a very high group velocity dispersion near the cutoff frequencies,which causes extensive pulse reshaping and broadening, in addition to multimode interference inthe time and frequency region. The majority dominant mode is a combination of the TE_1 (97.96 %)and the TM_0 (81.61 %) modes because the lowest mode has a small absorption and an incident evenfield pattern. Because each mode has different transmission and coupling coefficients, absorptionand propagation constant, the theoretical calculation for the total TM or TE modes requires asummation of the components. The theoretical calculation and the measured data fit well in thefrequency and time domain.