*Article* **Over-Two-Octave Supercontinuum Generation of Light-Carrying Orbital Angular Momentum in Germania-Doped Ring-Core Fiber**

**Jian Yang 1, Yingning Wang 1, Yuxi Fang 1, Wenpu Geng 1, Wenqian Zhao 1, Changjing Bao 2, Yongxiong Ren 2, Zhi Wang 1, Yange Liu 1, Zhongqi Pan 3 and Yang Yue 4,\***


**Abstract:** In this paper, we design a silica-cladded Germania-doped ring-core fiber (RCF) that supports orbital angular momentum (OAM) modes. By optimizing the fiber structure parameters, the RCF possesses a near-zero flat dispersion with a total variation of <±30 ps/nm/km over 1770 nm bandwidth from 1040 to 2810 nm for the OAM1,1 mode. A beyond-two-octave supercontinuum spectrum of the OAM1,1 mode is generated numerically by launching a 40 fs 120 kW pulse train centered at 1400 nm into a 12 cm long designed 50 mol% Ge-doped fiber, which covers 2130 nm bandwidth from 630 nm to 2760 nm at −40 dB of power level. This design can serve as an efficient way to extend the spectral coverage of beams carrying OAM modes for various applications.

**Keywords:** orbital angular momentum; nonlinear optics; supercontinuum
