Particle trapping and conveying using an optical archimedes’ screw

Trapping and manipulation of particles using laser beams has become an important tool in diverse fields of research. In recent years, particular interest has been devoted to the problem of conveying optically trapped particles over extended distances either downstream or upstream of the direction of photon momentum flow. Here, we propose and experimentally demonstrate an optical analog of the famous Archimedes’ screw where the rotation of a helical-intensity beam is transferred to the axial motion of optically trapped micrometer-scale, airborne, carbon-based particles. With this optical screw, particles were easily conveyed with controlled velocity and direction, upstream or downstream of the optical flow, over a distance of half a centimeter. Our results offer a very simple optical conveyor that could be adapted to a wide range of optical trapping scenarios.