Design of a high-birefringence photonic crystal fiber using an asymmetric defect in the fiber core

We numerically investigated a high birefringence photonic crystal fiber (PCF) which consists of the circular air holes in fiber cladding and a rotational ring of elliptical air holes in fiber core. Four different patterns (i.e., case A-D) of PCF structures have been investigated for comparison. The birefringence and mode field area of these PCFs have been numerically estimated by employing a finite element method (FEM). An endlessly single mode, high birefringence (~7.6×10^-3) is found at the excitation wavelength of λ=1550 nm. The merit of the designed PCFs is that their optimum birefringence can be easily achieved by introducing the rotational elliptical air holes in the fiber core region.