Low confinement loss photonic crystal fibre capable of supporting 54 orbital angular momentum modes

A novel structure photonic crystal fibre (PCF) supporting orbital angular momentum (OAM) modes is proposed. The transmission layer is a ring core with high refractive index, sandwiched between the inner air-hole cladding and the outer cladding composed of nonuniform air-holes periodically arranged in silica. The diameters of the air-holes in the outer cladding gradually increase in the radial direction. The simulation results show that the designed PCF is capable of supporting 54 OAM modes over the 650 nm bandwidth ranging from 1200 nm to 1850 nm, and possesses some advantages in low confinement loss and flat dispersion, that is, the confinement loss is low to the order of magnitude of and the dispersion slope is less than 0.2.