One of the most hallowed fantastical pieces of science fiction technology is the tractor beam. They are a ubiquitous feature in the space adventure genre, though seemingly impossible to replicate for any significant real world application--until now, on Earth, at least.
Laser physicists at Australian National University have constructed a tractor beam that can both repel and attract objects, like a sort of shield-tractor beam combo. The device uses what is known as a 'hollow' laser beam, which is "bright around the edges and dark in its centre," according to ANU.
This tractor beam is the only long-distance 'optical tractor beam' in existence, and it can move particles up to one fifth of a millimeter in diameter across distances up to 20 centimeters. Now, while that might not sound like a lot, it is, speaking relatively. In fact, this tractor beam can move particles nearly 100 times farther than any previous experiments of a similar nature.
One of the professors heading up the study at ANU's Research School of Physics and Engineering, Wieslaw Krolikowski, stated of the latest successful experiments: "Demonstration of a large scale laser beam like this is a kind of holy grail for laser physicists." The reason this new technique is so important is because it uses only one laser beam. Potential applications for the future could include repelling atmospheric pollutants or capturing particles for study using only laser beams.
And ANU's researchers are already thinking of applications for the tractor beam on a larger scale: "Because lasers retain their beam quality for such long distances, this could work over metres. Our lab just was not big enough to show it," stated study co-author Dr. Vladlen Shvedov.
Previous tractor beams have attempted to move particles by using photon momentum. However, the ANU device heats the surface of its targets and manipulates the relationship between the particles and the air around them to induce movement.
Hnatovsky went on to say, "We have devised a technique that can create unusual states of polarisation in the doughnut shaped laser beam, such as star-shaped or ring polarised," Dr Hnatovsky said.
"We can move smoothly from one polarisation to another and thereby stop the particle or reverse its direction at will."
Unfortunately, since this technology uses heated air molecules to move particles, that means it won't work in space. But that doesn't mean a space tractor beam won't one day be possible--we hope. For now we'll just have to settle for terrestrial tractor beams. Sigh. Although, if we can get that hyperdrive working, then we'll be living in the future, right?