We propose and numerically analyze various hollow-core antiresonant fiber (HC-ARF) for operation at terahertz frequencies. We compare typical HC-ARF designs with nested and adjacent nested designs while analyzing performance in terms of loss and single-mode guidance of terahertz waves. With optimized fiber dimensions, the fundamental core mode, cladding mode, core higher-order modes (HOMs), and the angle dependence of adjacent tubes are analyzed to find the best design for low loss terahertz transmission. Analysis of the fiber designs shows that the nested tube-based antiresonant fiber exhibits lower transmission loss and superior HOM suppression, exceeding 140. The nested HC-ARF is feasible for fabrication using existing fabrication technologies and opening up the possibility of efficient transmission of terahertz waves.
