Numerical Analysis on Birefringence of Photonic Crystal Fiber by Tuning Patterns and Infiltrating Materials of Innermost Air Holes

In this paper, we give a numerical analysis of a novel high-birefringence and low-confinement loss index-guiding photonic crystal fiber (PCF) using the finite element method by tuning patterns and filling the medium of innermost air holes. This PCF is composed of a solid silica core surrounded by six elliptical air holes and a cladding that consists of binary unit cells. The novelty of the proposed PCF structures is that the large elliptical air holes closest to the core have been rotated in different ways. Results show that the asymmetry in PCF cladding and the area of the PCF core are the key factors for determining the localization extent of the transverse mode. Modal birefringence values and confinement loss at the excitation wavelength of $\lambda =1.55$ μm can be easily achieved at a magnitude of the order of $10^{-2}$ and at less than 0.39 dB/km, respectively. From the viewpoint of numerical analysis, the effects of a material [with a refractive index ${