A "tractor beam," a long-standing icon of science fiction, is real and Australian researchers say they've set a record by dragging objects 100 times further than has been accomplished in previous experiments.
Not only have researchers at the Australian National University increased the distance an object can be moved, but their version of a tractor beam is reversible -- it can both pull and push objects.
"Demonstration of a large scale laser beam like this is a kind of holy grail for laser physicists," says Wieslaw Krolikowski of the university's Research School of Physics and Engineering.
While previous tractor beams have used the energy of photons to propel particles, they've been limited to moving extremely small object for just tiny distances.
The new tractor beam uses an alternate technique -- heat -- to move a much larger object over a much greater distance, up to almost 8 inches, the researchers report in the journal Nature Photonics.
They've used a hollow laser beam, bright around its edges but dark in its center, to heat up both the objects to be moved and the air around them.
With it they've been able to manipulate and guide hollow gold-covered glass spheres around 0.2 millimeters across, they say.
The laser beam heats up the spheres, creating hot spots on their surface.
Molecules of air hitting the hot spots heat up and then shoot away, with the spheres recoiling and moving in an opposite direction.
Moving the location of the hot spots by switching the laser beam's polarization allowed the researchers to control the direction of the movement.
"We can move smoothly from one polarization to another and thereby stop the particle or reverse its direction at will," study co-author Cyril Hnatovsky says.
"We have devised a technique that can create unusual states of polarization in the doughnut shaped laser beam, such as star-shaped (axial) or ring polarized (azimuthal)," he says.
Because their system only requires a single beam that can both pull and push, it's a versatile technology that could be effective in real-world applications such as removing pollutants from the atmosphere or extracting unwanted particles out of samples of materials, they said.
The technology can also be easily scaled up, they said.
"Because lasers retain their beam quality for such long distances, this could work over meters," study co-author Vladlen Shvedov said. "Our lab just was not big enough to show it."
