Linear to circular polarization conversion in the sharp focus of an optical vortex

We have shown that when sharply focusing a linearly polarized optical vortex with topological charge 2, in the near-axis region of focal plane, not only does reverse energy flow (the negative on-axis projection Poynting vector) occur, but also right-handed circular polariza-tion light. Moreover, due to spin-orbital angular momentum conversion, polarization vector and transverse rotate around axis same direction (counter-clockwise). If an absorbing spherical microparticle is put focus on axis, it will its center mass counterclockwise. Numerical simulation results confirms theoretical predictions.