Orbit-induced localized spin angular momentum of vector circular Airy vortex beam in the paraxial regime.

We theoretically study the propagation properties of the vector circular Airy vortex beam in detail. The results show that the orbital angular momentum can induce a localized spin angular momentum after autofocusing in the paraxial regime, which leads to an abrupt polarization transition just before the focal plane. However, there is no angular momentum conversion from orbital angular momentum to spin angular momentum during the whole propagation process. We provide an intuitive explanation for the appearance of such spin angular momentum localization. This investigation is expected to advance our understanding of the vector properties of circular Airy beam and optical spin-orbit coupling.