Abrupt polarization transition of vector autofocusing Airy beams

We experimentally and theoretically study the abrupt polarization transitions of vector autofocusing Airy beams associated with the spin-orbit interactions. It is shown that when the topological charges of the polarization and the attached spiral phase are equal in number, the local polarizations undergo an abrupt transition from linear to circular polarizations at the focal point, and the associated orbital angular momentum partially converts into the spin of photons. The experimental results are theoretically explained from the far-field properties of the beams in terms of Hankel transformations.