How To Turn A Laser Into A Tractor Beam

March 1, 2011 | Source: The physics ArXiv blog

Fudan University scientists have worked out how to generate a backward pulling force from a forward propagating beam.

it works only for beams in which the momentum in the direction of propagation is small, as is the case for beams that merely glance off an object. Second, the photons must simultaneously excite several multipoles within the particle, which scatter the beam.

If the scattering angle is just right, the total momentum in the direction of propagation can be negative, meaning the particle is pulled back towards the source and the light becomes a tractor beam.

Ref: Backward Pulling Force From A Forward Propagating Beam