One terahertz (THz) waveguide based on the metal rod array (MRA) structure is numerically demonstrated in 0.1–1 THz, including the fundamental and high-order transverse magnetic (TM) modes. The high-order TM-mode THz waves are strictly confined inside the MRA structure and are thus sensitive to the metal rod interspace for their spectral positions, bandwidths, transmittances, and attenuation coefficients. Arranging metal rods with fine-tuning the interspaces across the optic axis is presented as the critical stratagem to optimize the transportation efficiency of THz waves through an MRA structure. The maximum propagation length of MRA-confined THz waves is over 30 mm with the lowest attenuation coefficients of approximately 0.05–0.1 cm−1. The MRA is, therefore, applicable as one deformable artificial structure in THz frequency region because simply one-axial adjustment of the metal-rod interspace enables the modulation purpose without uniform adjustment on the two-dimensional metal rod interspace.
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