Design and optimization of high-birefringence low-loss crystal fiber with two zero-dispersion wavelengths for nonlinear effects

Abstract

A photonic crystal fiber (PCF) is proposed that is composed of a central defect core and cladding with elliptical air holes along the fiber length. In the structure, two circular air holes are enlarged near the central region to reduce core size and induce high nonlinearity. Its dispersion, birefringence, nonlinearity coefficient, and confinement loss are investigated simultaneously by using the full-vectorial finite element method with anisotropic perfectly matched layers. Numerical results indicate that the proposed PCF has two zero-dispersion wavelengths (ZDWs) and stronger confinement ability in its guide mode, in which the confinement loss is lower than 10−2 dB m−1. The two high-birefringence ZDWs can be optimized by adjusting the geometric parameters of the proposed fiber, such as air-filling fraction d/Λ and air-hole ellipticity η. With the fixed parameters d/Λ=0.6 and η=2.85, the two ZDWs are present in the communication window, and the corresponding birefringence and nonlinearity coefficient are as high as 4.8×10−2 and 105 W−1 km−1, respectively. The proposed two-ZDW PCF with high birefringence and nonlinearity will have important applications in four-wave mixing and higher-order dispersion effects.