A long-range polarization-controlled optical tractor beam

The laser beam has become an indispensable tool for the controllable manipulation and transport of microscopic objects in biology, physical chemistry and condensed matter physics. In particular, 'tractor' laser beams can draw matter towards a laser source and perform, for instance, all-optical remote sampling. Recent advances in lightwave technology have already led to small-scale experimental demonstrations of tractor beams^1-4. However, the realization of long-range tractor beams has not gone beyond the realm of theoretical investigations^5-9. Here, we demonstrate the stable transfer of gold-coated hollow glass spheres against the power flow of a single inhomogeneously polarized laser beam over tens of centimetres. Additionally, by varying the polarization state of the beam we can stop the spheres or reverse the direction of their motion at will.