Pulling beam is the specially–shaped optical ray characterized in that, that acting to a certain passive particle in vacuum, the ray pulls the particle in the direction, opposite to the mean direction of the beam propagation.
The existence of a pulling beam is counter-intuitive because the scattered photons should carry out more momentum than they had before the interaction. Nevertheless, in century 21, the existence of the pulling beams beams is suggested and discussed .
As in the case of the superluminal wave packets, the Besselian beam is used to construct the example of the pulling beam. The paradoxes and the resulting discussions arise from the fussy definition of terms optical beam and the wave packet. As the superluminal wave packet is an analogy of the light–spot, the pulling beam arises as special superposition of waves, that scatter mainly into the mean direction of propagation. The resulting force is quadratic with respect to the numerical aperture of the pulling beam and disappears in the paraxial approximation.
- http://arxiv.org/pdf/1102.4905v1 Jun Chen, Jack Ng, Zhifang Lin, and C. T. Chan. Backward Pulling Force from a Forward Propagating Beam. (2011)