Precise position and angular control of optical trapping and manipulation via a single vortex-pair beam

Optical trapping and manipulation using structured laser beams now attract increasing attention in many areas including biology, atomic science, and nanofabrication. Here we propose and demonstrate experimentally the use of a single vortex-pair beam in two-dimensional optical trapping and manipulation. Using the focal properties of such vortex-pair beams, we successfully manipulate two spherical microparticles simultaneously, and obtain the precise position-control on the microparticles by adjusting the off-axis parameter a of the vortex-pair beam. Furthermore, we also realize the high-precision angular-controllable rotation of cylindrical microrods by rotating the initial phase structure of such vortex-pair beams, which is like an optical wrench due to two focused bright spots at the focal plane of objective lens. Our experimental result provides an alternative manipulation of microparticles and may have potential applications in biological area, and optically driven micromachines or motors.