Photokinetic Effects: The leap from optical tweezers to practical tractor beams
David G. Grier, Department of Physics and Center for Soft Matter Research, New York University


The recently developed theory of photokinetic effects reveals how variations in amplitude, phase and polarization influence the forces and torques that beam of light exert on illuminated objects. This theory is put into practice through holographic optical trapping in which computer-generated holograms are used to project specifically structured beams of light onto micrometer-scale samples. This interplay of theory and technology has yielded the first experimental demonstration of a knotted force field and, more recently, the first practical realization of a tractor beam, a propagation-invariant traveling wave that can transport illuminated objects back to its source.  This talk sketches out the theory of photokinetic effects and leads up to the development of optical solenoid beams, a previously unrecognized complete set of propagation-invariant modes of light, some of whose members act as tractor beams.