- Researchers have so far managed to move microscopic spheres of silica suspended in water over distances of 30 micrometres
- But Nasa have already been in touch…
By Damien Gayle
PUBLISHED: 11:37 EST, 24 October 2012 | UPDATED: 13:41 EST, 24 October 2012
Star Date 24102012: We have detected evidence of a working tractor beam.
Two physicists working at New York university have developed a technique for using beams of light to draw a particle toward a source and claim to have demonstrated it experimentally.
Professor David Grier and David Ruffner, a graduate student, working at the Department of Physics and Centre for Soft Matter Research say they have realised the Star Trek-style technology – only on a miniscule scale.
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Whenever a friendly star ship was in distress, it was no problem for the crew of the Enterprise to activate their tractor beam and drag the vessel to safety.
However, until now the technology has remained beyond the reach of real-world physicists, with the best they could manage being laser-based tweezers that can drag particles across microscopic distances in two dimensions.
Now in a paper published in the journal Physical Review Letters – and available in full here – Professor Grier and Mr Ruffner describe a technology that goes one better, by actually pulling particles towards their beam’s source.
It is well known that light can push objects – a property that forms the basis for the idea of using solar sails – but getting light to drag something has so far proved to be more difficult.
The NYU tractor beam is based on Chinese research published last year into a kind of laser called a Bessel beam, which emits light in concentric rings.
That study calculated that a such a beam could be designed to make a particle inside it emit photons on the side facing away from the beam’s source, forcing the particle to recoil towards that source.
No-one has as yet been able to make such a beam, but the NYU researchers got around the problem by instead projecting two Bessel beams side by side down a microscope and using a lens to angle them so they overlap.
By varying the relative phase of the two beams, this technique traps the particle in a moving hologram they call an ‘optical conveyor’ which allows ‘bi-directional transport in three dimensions’.
New Scientist explains how projecting the beams in this way creates a pattern of alternating bright and dark regions. By fine tuning the beam photons in the bright regions which flow past the chosen particle can be made to scatter backwards, hitting the particle and knocking it on towards the next bright region.
However, the beam is not quite ready to snare a starship. Professor Grier and Mr Ruffner demonstrated their technology by moving microscopic spheres of silica suspended in water over distances of 30 micrometres.
‘This is still very much in its infancy,’ Mr Ruffner told New Scientist. Nevertheless it opens the door to transforming science fiction into science fact – and Nasa has already been in touch.