title: Design and optimization of broadband and polarization-insensitive dual-core photonic crystal fiber coupler.
abstract: In this paper, we propose a novel (to our knowledge) broadband and polarization-insensitive dual-core photonic crystal fiber (PCF) coupler through the introduction of an elliptical-shaped central air hole to offset the slight birefringence arising from the dual core. With a full vectorial finite element method and anisotropic perfectly matched layers as the external boundaries, the impact of several fiber parameters on the coupling characteristics of dual-core PCF is investigated in detail. Through optimizing the main fiber parameters, including core diameter, size and ellipticity of the central air hole, and refractive index difference, broadband and polarization-insensitive characteristics are achieved in the wavelength range from 0.8 to 1.7 μm. The variation of the coupling ratio is stabilized at 50±1%, and the coupling ratio difference between x polarization and y polarization is less than 2% over the wavelength range. This dual-core PCF makes it easier to develop a 3 dB coupler over a wide wavelength for passive optical networks and large optical systems.
authors.affiliation: Key Lab of All Optical Network & Advanced Telecommunication Network of Ministry of Education of China, Beijing Jiaotong University, China. shqlou@bjtu.edu.cn
authors.forename: Shuqin
authors.initials: S
authors.lastname: Lou
authors.forename: Zunwei
authors.initials: Z
authors.lastname: Tang
authors.forename: Liwen
authors.initials: L
authors.lastname: Wang