Terahertz Tube Lattice Fibers With Octagonal Symmetry

A new hollow core fiber for terahertz applications consisting of dielectric tubes arranged with an octagonal symmetry is presented. Simulation results have shown that this fiber exhibits an effectively single-mode propagation with lower propagation loss with respect to hollow core fibers with a hexagonal symmetry. The suppression of higher order modes is due to a better phase-matching condition with cladding modes propagating into the hollow core of tubes. In particular, by using tubes with 44-μm thickness and outer diameters as low as 0.5 mm, a rejection of high order modes higher than 20 dB/m and fundamental mode propagation loss lower than 5 dB/m from 2.30 to 2.85 THz can be obtained.