LAUSR

Abstract This paper proposes a modified segmented cladding fiber with two-layer high-index rings in the core. The inner high-index ring helps to increase the loss ratio between the higher-order modes (HOMs) and the fundamental mode (FM) to achieve single-mode operation. The outer high-index ring is beneficial to improve the waist of the electric field distribution of the FM to enlarge the mode area. The simulation results show thanks to the joint defect of these two-layer high-index rings, the defect of the RR-SCF that can’t provide single-mode operation in all bending orientations is made up. Effective single-mode operation is achieved at a tight bending radius of 15 cm when the operating wavelength ranges from 1.06 μ m to 1.58 μ m. The mode area of the fiber operating at 1.06 μ m is markedly enlarged to 835 μ m2. This new fiber shows great potential in compact high-power fiber lasers and amplifiers.