Manipulation of aerosols revolving in taper-ring optical traps.

We designed taper-ring optical traps by a weakly focused laser beam through a circular aperture. By railing-like potential barriers, these optical traps are partitioned into enclosed rings, in which irregular light-absorbing microparticles can be driven by photophoretic force to revolve around optical axis in air. The diameter of revolution can reach about 700 μm, which is much larger than that in traditional optical traps based on radiation pressure and gradient force. More importantly, multiple particles were driven to revolve simultaneously in different planes in air for the first reported time to the best of our knowledge.