Supercontinuum generation with extended bandwidth and improved purity in graded-index ring-core fiber
摘要
In this paper, we numerically investigate the impact of shape factor (k) on the mode properties of graded-index ring-core fiber (GIRCF). A 50 mol% Ge-doped GIRCF with shape factor of 2 is devised to generate supercontinuum (SC) carrying orbital angular momentum (OAM) modes, which possesses flat dispersion with a minor variation of < ± 30 ps/nm/km from 1090 to 2590 nm. The generated supercontinuum (SC) in the designed GIRCF carrying OAM1,1 mode covers 2305-nm wavelength range from 750 to 3055 nm at − 40 dB level. The graded refractive index profile (RIP), introduced as a new parameter, offers an additional dimension for the design of ring-core fiber (RCF) supporting OAM modes. The graded RIP contributes to the creation of flat and near-zero dispersion in the RCF structures and reduces the spin–orbit coupling (SOC) effect at the material boundary, leading to broader spectral coverage and higher mode purity in the output spectra.