Chiral-resonance-induced asymmetric spin-orbit mapping effect in twisted few-mode hollow-core anti-resonant fiber.

We investigate the interaction between the spin and orbital angular momentum (OAM) of light in a few-mode hollow-core anti-resonant fiber (HC-ARF). Due to the lifted degeneracy of TM01/TE01 modes and retained degeneracy of HE21 modes, the left- and right-handed circularly polarized LP11-like beams can be transformed into linearly polarized OAM modes carrying topological charges of +1 and -1, respectively, in an untwisted HC-ARF. However, since one of the vector OAM eigenmodes supported by the twisted HC-ARF couples strongly with the cladding leaky mode, only the right-handed circularly polarized LP11-like beam yields a linearly polarized OAM mode with a topological charge of -1. By employing our developed code for the full-vector finite-element beam propagation method, we have demonstrated the OAM-resonance-induced asymmetric spin-orbit mapping effect in twisted HC-ARFs. Our work opens a path for designing HC-ARF-based integrated devices for important applications, such as optical vortex generation.