Design of high birefringence and low confinement loss photonic crystal fibers with five rings hexagonal and octagonal symmetry air-holes in fiber cladding

We present a new cladding design for high birefringence and low confinement loss photonic crystal fibers (PCFs) using a full-vector finite element method with anisotropic perfectly matched boundary layer. Six cases of PCFs are proposed for comparison. The proposed cladding in PCFs is composed of five rings of air-holes. Air-holes on the inner two rings are arranged in a hexagonal symmetry whereas, air-holes on the outer three rings are arranged in an octagonal symmetry in fused silica. Results show that suitable design air-holes on the inner two rings will significantly increase the birefringence, whereas, elliptical holes with major axis along x-axis on the outer three rings will provide strong confinement ability. The highest modal birefringence and lowest confinement loss of our proposed case five structure at the excitation wavelength of lambda = 1550 nm can be achieved at a magnitude of 0.87 x 10(-2) and less than 0.01 dB/km with only five rings of air-holes in fiber cladding. (C) 2011 American Institute of Physics. [doi:10.1063/1.3583560]