'Tractor beam' is possible with lasers, say scientists (BBC)

[eppur_se_muova]

A laser can act as a "tractor beam", drawing small objects back toward the laser's source, scientists have said.

It is known that light can provide a "push", for example in solar sails that propel spacecraft on a "wind of light".

Now, in a paper on the Arxiv server, researchers from Hong Kong and China have calculated the conditions required to create a laser-based "pull".

Rather than a science fiction-style weapon, however, the approach would only work over small distances.

The effect is different from that employed in "optical tweezers" approaches, in which tiny objects can be trapped in the focus of a laser beam and moved around; this new force, the authors propose, would be one continuous pull toward the source.
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more: http://www.bbc.co.uk/news/science-environment-12620560

http://arxiv.org/abs/1102.4905

[benld74]

1. MAKE IT SO #1

[DetlefK]

2. tractor beam is overstatement (unless you want to harvest dust particles)

Page 3 of document: A laser-beam with vanishing z-momentum (e.g. a Bessel-beam) is used to induce multipoles in a particle. Those multipoles emit photons and the recoil force pushes the particle towards the laser.

Page 4: The particle must have a particular electric permittivity epsilon-r. The Bessel-Beam must have a particular configuration.

page 6, figure 3: On polystyrol it only works for very specific particle radii (micrometer-range!).

[WatsonT]

3. With lasers anything is possible