Low-loss polarization-maintaining hollow-core anti-resonant terahertz fiber

Polarization-maintaining terahertz (THz) fibers have been considered as fundamental elements in polarization sensitive THz systems. Based on the anti-resonant waveguiding mechanism, we propose a low-loss polarization-maintaining hollow-core THz fiber with four half-elliptical cladding membranes. Numerical simulations indicate that birefringence of the fundamental mode group could be introduced by modifying the thickness of a pair of membranes while sacrificing available low-loss bandwidth. We observe that the core size, the dimension and shape of cladding membranes, have significant impacts on modal properties. For the half-circular membranes based fiber with optimized parameters, the attenuation coefficients of fundamental modes are below 10 dB m^-1, the birefringence is above 10^-4 and the group velocity dispersion values are lower than 60 ps THz^-1 m^-1 within the frequency bandwidths of 0.46-0.6 THz and 0.74-1.1 THz. At 0.9 THz, the lowest attenuation coefficient is 0.5 dB m^-1 with birefringence of 1.52 × 10^-4. Moreover, this THz fiber is insensitive to neither x- nor y-direction bend with a bend radius no less than 2 cm.