Design of Highly Birefringent and Low-Loss Oligoporous-Core THz Photonic Crystal Fiber With Single Circular Air-Hole Unit

A novel strategy to design a highly birefringent and low loss oligoporous-core THz photonic crystal fiber (PCF) by introducing a single circular air-hole unit into the core area has been revealed. The circular air-hole units can be diversely designed as dual-hole, triple-hole, or other simple anisotropic structures. The characteristics, including birefringence, effective material loss, power fraction, confinement loss, and dispersion, are numerically analyzed in detail based on the full-vector finite element method (FEM). Simulation results show that birefringence up to the order of 3 × 10 −2 and low effective material loss down to 20–40% of its bulk material loss could be achieved in a wide frequency range. The newly proposed THz PCF facilitates the fabrication process due to their simple structures with all circular air-holes and may find wide applications in sensing or polarization maintaining transmission systems.