The characteristics of vortex modes in twisted fiber with dielectrically chiral ring core

A novel twisted ring core fiber incorporating chiral material into the ring core is proposed, which supports orbital angular momentum (OAM) modes. Results show that between chirality and twist rate there exist a cooperative effect in birefringence and a competitive effect in mode index bifurcation between OAM modes with different helicity. The cooperative effect between chirality and twist rate also breaks the degeneracy within OAM modes of the same or opposite helicity while preserving the vectorial nature of the modes. The OAM modes generated by twisted dielectrically chiral fiber are less likely to have crosstalk. The dependences of OAM modes birefringence on chirality and twist rate are investigated. Additionally, the mode effective index bifurcation as a function of wavelength is also discussed under both kind of chirality. Owing to high birefringence, good refractive index bifurcation, we believe that this kind of fiber can find applications in new kind of OAM mode generators, OAM mode filters, optical communication, and sensing.