We theoretically compare two kinds of spin-orbit interaction (SOI) systems in optics, one is that a light beam propagates along the optical axis in a uniaxial crystal, and the other is that it is normally reflected/refracted by a sharp interface. We find that the vortex phases generated by these processes are wavevector-dependent Pancharatnam-Berry phases originating from the topological nature of the beam itself, while the Pancharatnam-Berry phase in an inhomogeneous anisotropic medium (e.g., Q-plates) is coordinate-dependent resulting from the anisotropy of the external materials. We further discuss the SOI efficiency of these systems, and propose several ways to enhance them.
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