Design and analysis of a dispersion flattened and highly nonlinear photonic crystal fiber with ultralow confinement loss.

We present a novel and robust design for a photonic crystal fiber with flattened dispersion, a highly nonlinear coefficient, and low confinement loss for its dual concentric core structure. The proposed fiber has a modest number of design parameters. Analysis results show that the proposed eight-ring photonic crystal fiber is obtained with a nonlinear coefficient greater than 33 W(-1) km(-1) and a near-zero dispersion slope of -7.828 x 10(-4) ps/nm(2)/km at 1550 nm. Ultraflat dispersion with a value between -1.380 and +0.9860 ps/nm/km and a superlow-order confinement loss of 10(-4) dB/km are simultaneously obtained ranging from 1400 to 1625 nm. For practical fabrication, the influence of random imperfections of airhole diameters on dispersion and nonlinearity is discussed to verify the robustness of our design.