Fig. 1. Image of hollow-core terahertz waveguide structure with partial negative curvature

Fig. 2. Power distribution of x and y polarization modes at 0.35 THz

Fig. 3. The loss of x and y polarization modes versus frequency

Fig. 4. Test and schematic diagram of terahertz time-domain spectroscopy system

Fig. 5. Frequency domain signal with two-length waveguide rotating at 0°, 180°, and 360°

Fig. 6. Frequency domain signal with two-length waveguide rotating at 90°, 270°

Fig. 7. The experimentally measured loss of x and y polarization modes