We experimentally demonstrate the possibility of quasi-adiabatic conversion of modes to vortex modes in a twisted highly birefringent fiber with a gradually increasing twist rate. Based on the value of the effective indices, the modes are selectively converted to right- and left-handed circularly polarized vortex modes with a total angular momentum of ±2 and to quasi-/ modes with a total angular momentum of 0. Since the proposed conversion method has a purely topological origin, it is broadband in nature, in contrast to the methods based on resonant effects.
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