Laser beams normally cut, burn and push, but by fine tuning a laser, researchers have found a way to create a real tractor beam.
For years scientists have known that light pushes. Planetariums and gadget stores have sold small glass globes with vanes painted black on one side and white on the other that—when exposed to light—begin to spin from the push of photons. Solar sail technology works the same way, the sail being pushed by the “solar wind” that is basically light.
Determining that if light can push it might also be made to pull, Chinese physicists have managed to create a laser that tugs objects towards the light source. Their research paper, “Backward Pulling Force from a Forward Propagating Beam” is available here: http://arxiv.org/ftp/arxiv/papers/1102/1102.4905.pdf
At the present, the effect can work only over short distances, but in the future the concept may allow a beam to grab and pull larger objects much greater distances.
Laboratory experiments by other researchers have achieved what is known among research scientists as “optical tweezers.” The laser beam in those experiments was made to successfully capture tiny objects and maneuver them about. This new application, the authors claim, permits the beam to pull objects towards the beam source with one constant force.
The researchers explain that it works by using a special type of laser that produces a “Bessel beam.” This unique beam differs from ordinary lasers by producing ripples creating a precise pattern of waves with peaks and valleys. Using such a beam projected at an object using an oblique angle permits the ripples to be tuned, capturing and holding an object. Once caught in the laser’s embrace, the object can be pulled toward the source by continuous tuning of the light ripples.
In essence, the light refracted by the atoms of the object that are sent forward create an interference and a push back, sending the object backwards towards the beam source.
Contacted about the experiment by the BBC, Ortwin Hess at Imperial College London labeled the idea “fascinating.” He stated that the research work “takes a radical idea forward.”
Drawing an analogy between an object, the Bessel beam, and a boat in water, Hess said, “It’s a bit like a boat moving through water. In the eddies you generate as part of that forward movement, there are areas that literally seem to be pulling back. [Because] the ship has a shape, you get these backward eddies at the side; in a similar way if you have a Bessel beam you have certain areas that do the same thing.”
The tractor beam has been a staple of science fiction stories for many decades. It’s broadest use was in the famous Lensman series by author E. E. ‘Doc’ Smith.
Decades later, Gene Roddenberry incorporated tractor beam technology as part of the starship technology aboard the starship Enterprise.
So, now that the tractor beam has been invented all that’s needed is the Enterprise, a warp drive, and a Starfleet captain to command her.
