High-Birefringence Low-Loss Hollow-Core THz Waveguide Embedded Parallel Slab Cladding

A novel high-birefringence and low-loss hollow-core (HC) antiresonant (AR) THz waveguide is proposed and experimental demonstrated. The waveguide is a circular tube embedded with two pairs of symmetrical parallel slabs. With the support of a circular tube, one pair of slabs near the waveguide center is used to form a rectangular-like core to achieve high birefringence, and another pair of slabs is placed in the cladding to further reduce the waveguide loss. Simulation results indicate that the birefringence reaches the magnitude order of 10
⁻³
within the transmission window from 0.38 to 0.50 THz. The highest birefringence reaches 3.42 × 10
⁻³
at 0.38 THz with a loss of 0.09 cm
⁻¹
. We manufacture the HC-AR THz waveguide with photosensitive resin by using three-dimensional printing technology. And the waveguide properties are investigated by THz time-domain spectroscopy system. Experimental results demonstrate that the birefringence variation of the HC-AR THz waveguide is within the range of 1.57 × 10
⁻³
to 4.77 × 10
⁻³
in the 0.39 to 0.51 THz transmission window. The highest birefringence is up to 4.77 × 10
⁻³
at 0.39 THz and the corresponding loss is 0.12 cm
⁻¹
. To the best of authors’ knowledge, the proposed HC-AR THz waveguide achieves the highest birefringence and relatively low loss in current HC-AR THz waveguides.