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.

OAM mode generation in helically twisted hollow-core antiresonant fiber.

We investigate the orbital angular momentum (OAM) mode-generating process of a long-period onefold chiral fiber grating (L-1-CFG) based on a helically twisted hollow-core antiresonant fiber (HC-ARF). Taking the right-handed L-1-CFG for an example, we theoretically and experimentally prove that the first-order OAM mode can be generated by only inputting a Gaussian beam. We fabricated three right-handed L-1-CFG samples based on the helically twisted HC-ARF with twist rates (α) of -0.