Porous photonic-crystal fiber with near-zero ultra-flattened dispersion and high birefringence for polarization-maintaining terahertz transmission

Abstract One unique kind of porous-core photonic crystal fiber (PCF) is proposed with elliptical air-holes in core, and round-corner hexagonal air-holes in cladding, for efficiently transmitting polarization-maintaining terahertz waves. Dispersion, birefringence, effective material loss (EML) and confinement loss are investigated by using the full-vector finite element method (FV-FEM) with anisotropic perfectly matched layers. The numerical results indicate that its near-zero ultra-flattened dispersion (-0.01±0.06 ps/THz/cm) and birefringence higher than 7.0×10−2 (highest birefringence of 7.4×10−2 at 1.2 THz) can be achieved simultaneously over almost the same frequency range of 0.75–1.6 THz, with a low EML (0.08 cm−1 at 1.2 THz) and a low confinement loss (3.2 × 10-13 cm−1 at 1.2THz). Important modal properties, such as power fraction and effective mode area, are discussed, and the tolerance in fabrication is analyzed to indicate the feasibility of the proposed terahertz waveguides with PCF structure in manufacturing.