3D-printed high-birefringence THz hollow-core anti-resonant fiber with an elliptical core.

A high-birefringence and low-loss terahertz (THz) hollow-core anti-resonant fiber (THz HC-ARF) is designed and analyzed numerically by the finite element method (FEM). The THz HC-ARF is composed of an elliptical tube as the core for high birefringence guidance and a pair of symmetrical slabs arranged vertically as the cladding to attain low loss. Numerical analysis indicates that the birefringence reaches 10 in the transmission window between 0.21 and 0.35 THz. The highest birefringence is 4.61 × 10 at 0.21 THz with a loss of 0.15 cm. To verify the theoretical results, the THz HC-ARF is produced by three-dimensional (3D) printing, and the transmission characteristics are determined by THz time-domain spectroscopy (THz-TDS). High birefringence in the range of 2.17 × 10 to 3.72 × 10 and low loss in the range of 0.12 to 0.18 cm are demonstrated experimentally in the 0.2 to 0.27 THz transmission window. The highest birefringence is 3.72 × 10 at 0.22 THz and the corresponding loss is 0.18 cm. The THz HC-ARF shows the highest birefringence besides relatively low loss compared to similar THz HC-ARFs reported recently.