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 th...
