A novel photonic crystal fiber with near-zero flat dispersion

A novel photonic crystal fiber (PCF) based on pure silica is proposed to transmit 34 orbital angular momentum (OAM) modes in the wavelength range of 1.2 μmm~1.7 μm. The mode purity of the OAM modes is concentrated at 99.22%, and can reach up to 99.60%. The effective refractive index separation is up to 10^-3, which makes the mode degeneracy can be almost neglected. The dispersion variations are less than 23.73 ps·nm^-1·km^-1, and absolute value of chromatic dispersion is as low as 0.6 ps·nm^-1·km^-1. This structure also achieves a relatively large mode field area, a small nonlinear coefficient, and low confinement loss. In addition, the design features a simple structure, uses a single material, and has no element doping, fully taking into account the actual production difficulty and cost of photonic crystal fibers.