Regulation of Radial Higher-Order Orbital Angular Momentum Mode Based on Helically-Twisted Elliptic Fiber

Based on mode coupling theory and angular momentum matching principle, the generation process and mechanism of radial higher-order orbital angular momentum (OAM) based on helically-twisted elliptic fiber (HTEF) is analyzed. High-precision HTEFs are successfully fabricated using the arc discharge technology of a fusion splicer. By changing the twisted rate of the HTEF, OAM $-2n$ with radial order $n$ of 2, 3, 4 and 5 are successfully generated at 1550 nm. Subsequently, we compare the differences in twisted rates between simulations and experiments.