A kind of polymer tube with (elliptical) ring structure is proposed for Terahertz (THz) guiding. The THz polymer tube
has the low-loss property due to the fact that the central air core of the polymer tubes traps a large part of the mode
power. Properties such as the effective index and the relative absorption loss of the THz polymer tube are investigated.
The elliptical polymer tube with a cross-section of elliptical ring structure can be used as a highly birefringent low-loss
THz waveguide with a high birefringence (up to the order of 0.01). The birefringence property of the elliptical polymer
tubes with different parameters is also calculated and discussed.