Low loss, low dispersion and highly birefringent terahertz porous fibers
  We demonstrate that porous fibers have low effective material loss over an extended frequency range, 4.5 times larger bandwidth than that can be achieved in sub-wavelength solid core fibers. We also show that these new fibers can be designed to have near zero dispersion for 0.5-1 THz resulting to overall less terahertz signal degradation. In addition, it is demonstrated that the use of asymmetrical sub-wavelength air-holes within the core leads to high birefringence ~0.026. This opens up the potential for realization of novel polarization preserving fibers in the terahertz regime. 
Shaghik Atakaramians, Shahraam Afshar V., Bernd M. Fischer, Derek   Abbott, and Tanya M. Monro