Orbital angular momentum modes in twisted anti-resonant fiber with dielectrically chiral tube cores

Abstract We propose and investigate a twisted dielectrically chiral anti-resonant fiber (TCARF) by introducing chiral media into the inner core of six cladding tubes to generate orbital angular momentum (OAM). The numerical results show that the combined effects of structural chirality (twisting) and dielectric chirality lift the mode degeneracy within the same mode order both in the core and tube. Consequently, the effective refractive indices of the core modes and tube modes experience a refractive index splitting. Besides, the mode couplings between the core modes and tube modes were also tuned by the dielectric chirality parameter and twist rate. Additionally, the combined effects of twist rate and dielectric chirality result in differential confinement loss between the same modes belonging to the same mode group and a shift in the confinement loss peaks of OAM modes with opposite handedness. This differential loss between OAM modes with opposite handedness results in polarization filtering. The working wavelength of the filter ranges from 1.5 μm to 1.6 μm by varying the chirality parameter. The ARF we proposed in this paper can selectively filter out the polarized light in one direction by adjusting the chirality parameter in the tube core.