Tractor beam created: the ‘holy grail for laser physicists’

Laser physicists have built a reversible tractor beam and are using it to retrieve tiny particles.

It has nowhere near the pulling power of tractor beams envisaged in science fiction, but the first long-distance optical tractor beam has so far moved particles one fifth of a millimetre in diameter a distance of up to 20cm.

That’s about 100 times further than previous experiments, says Wieslaw Krolikowski of Australian National University.

“Demonstration of a large scale laser beam like this is a kind of holy grail for laser physicists,” Krolikowski says in a statement.

The beam can repel and attract objects using a hollow laser beam that is bright around the edges and dark in its centre.

Energy from the laser hits the particle and travels across its surface, where it is absorbed creating hotspots on the surface. Air particles colliding with the hotspots heat up and shoot away from the surface, which causes the particle to recoil in the opposite direction.

It is versatile, requiring only a single laser beam and could be used in controlling atmospheric pollution or for the retrieval of tiny, delicate or dangerous particles for sampling.

Co-researcher Vladlen Shvedov can also imagine the effect being 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,” Shvedov said.