A low-loss polarization-maintaining terahertz fiber

A novel low-loss THz polarization-maintaining fiber is analyzed numerically. The proposed fiber consists of two small thin dielectric tubes nested in a large dielectric tube. Numerical simulations performed using the full-vector finite element method show that the difference between the effective refractive index of LPx 01 and the adjacent modes is up to 10−2 orders of magnitude in the frequency range from 0.32 to 0.7 THz. At the same time, the proposed fiber has low loss characteristics, and the total loss of LPx 01 is only 0.17 dB/cm at 0.35 THz. In addition, near-zero flat dispersion of 0.3 ± 0.36 ps/THz/cm can be achieved by adjusting the structural parameters of the fiber.