Eight-Capillary Cladding THz Waveguide with Low Propagation Losses and Dispersion

We investigated the perspectives of a hollow core fiber with a cladding of eight polypropylene capillaries that provides flexibility, low propagation losses, and a single-mode regime in the terahertz frequency range. Optimization procedure is developed. The 7-dB/m propagation loss for 1.3-mm core size and 20-cm waveguide length is experimentally demonstrated at 22.2 THz frequency band. The measured group velocity dispersion do not exceed 1 ps/(THz.cm). The theoretical calculations based on the method of Green's functions confirm the experimental data, demonstrate the influence of capillary radius and wall thickness and predict 1.7-dB/m propagation losses for optimized geometry.