It appears that Australian physicists are very close to having developed the world’s first ever long-distance optical tractor beam which is reported be capable of both repelling and attracting objects.

An actual functional tractor beam is one of those sci-fi –type technologies that both scientists, and sci-fi geeks alike, have only ever been able to dream about. It’s this sort of thing only found on the screen in the Star Wars films, the kind that they use to irresistibly reel in space ships with. Howver, it seems that scientist working at the Australian National University in the nation’s capital, Canberra, are now a large step closer to creating a tractor beam that is able to both repel and attract objects.

In a press release, one of the researchers at the university, Wieslaw Krolikowski said, “Demonstration of a large scale laser beam like this is a kind of holy grail for laser physicists,” according to the Science Alert website.

The recent developments are quite impressive in that, the new tractor beam consists of only one hollow laser beam that is bright around the edges and dark in the centre, is capable of moving particles one hundred times further than previous experimental efforts. It looks as though it is actually the first long-distance optical tractor beam ever to be created. The scientists have managed to get the beam to move gold-plated glass particles one fifth of a millimetre in diameter, a distance of up to twenty centimetres.

The technology could have serious practical implications. It would appear that the technique could be used to help control atmospheric pollution by filtering tiny and delicate particles out of the air. But that will not be the extent of things, as the scientists also believe the tractor beam could be scaled up.

“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,” explains co-author Vladlen Shvedov in the release, according to Science Alert.

In previous efforts, tractor beams have been created in water, or have relied on momentum within the photons, or particles of light, in order to make the objects move. The new method however, works by relying on the energy from the laser heating up the particles and the air around them.

The research was conducted using gold-coated hollow glass particles which become trapped in the dark centre of the laser beam. Energy from the laser then hits the particle and travels across its surface, where it is absorbed and creates hotspots. Then, as air collides with these hotspots, it moves away from the surface which causes the particles to move in the opposite direction.
To manipulate the particle in terms of its movement either towards or away from the tractor beam, the team control the polarisation of the laser beam to change the position of the hotspot.
Co-leader of the study Cyril Hnatovsky explained, "We have devised a technique that can create unusual states of polarisation in the doughnut shaped laser beam, such as star-shaped (axial) or ring polarised (azimuthal). We can move smoothly from one polarisation to another and thereby stop the particle or reverse its direction at will,” he said.