Generation of the radial higher-order orbital angular momentum mode in helically twisted elliptic fiber

The generation mechanism and regulation method of the radial higher-order orbital angular momentum (OAM) mode based on helically twisted elliptic fiber (HTEF) are investigated. This work aims to reveal the quantitative relation between the twisted rate (α) and the target radial higher-order OAM mode. From theoretical simulations, it is concluded that α is the key to regulating the radial higher-order OAM mode. In the experiment, OAM2n modes with radial higher-order n of 2, 3, 4, and 5 are successfully generated at 1550 nm by regulating α of the HTEF. Finally, the transmission spectrum and purity measurements are performed for the OAM24 mode, and it can be concluded that the fabricated experimental samples have more than 90% conversion efficiency and close to 94% purity under the appropriate α and twisted length. © 2024 Optica Publishing Group. All rights, including for text and data mining (TDM), Artificial Intelligence (AI) training, and similar technologies, are reserved.