Rotating of metallic microparticles with an optimal radially polarized perfect optical vortex

We report an optical rotating of metallic microparticles using an optimal radially polarized perfect optical vortex (RPPOV). Due to its polarization structure, the RPPOV's transverse intensity exhibits two rings separated by roughly a wavelength. We show both numerically and experimentally that a metallic microparticle immersed in such a double-ring vortex develops two radial equilibrium positions, at either of which the particle can experience a non-zero azimuthal force, thus leading to a simultaneous rotation of the metallic microparticles about the optical axis at two orbits with different radius. Furthermore, the rotation radius and velocity can be separately controlled by changing the parameters of the RPPOV.