Using a laser-based tractor beam, physicists were able to move particles 0.2 millimeters in diameter up to 20 centimeters (almost 8 inches). Although the particles are small, the breakthrough is huge.
For those not well acquainted with science fiction terminology, a tractor beam is a beam of energy that can move objects or hold them stationary. Although the idea and term “tractor beam” was first introduced in 1931 in the magazine Amazing Stories, the Star Trek franchise brought the hypothetical idea to mainstream audiences.
According to CNET, the Research School of Physics and Engineering at the Australian National University (ANU) chose to use lasers as their energy source. On the surface, using lasers sounds like obvious way to move particles, simply use the force of the photons to push them. That’s partially what physicists at the University of St. Andrews did in their own pursuit to create a working tractor beam.
But ANU used a new revolutionary technique. The team used the doughnut-shaped laser beam, one that is dark or hollow on the inside to surround particles in energy. The team would then heat-up certain spots on the particles and when air particles hit the heated spots, they would shoot away and creating a recoil effect. The physicists could control the direction by changing where the particles were heated.
How do they control where to heat a tiny 0.2 millimeter particle?
As ANU’s Dr. Cyril Hnatovsky explains, it’s complicated.
“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.”
It doesn’t quite sound like the tractor beam in Star Trek, if they had to heat up part of a space-ship that would cause more problems then it’d solve. But it is progress, and the ANU hollow laser technique is a big step forward.
That 20 cm of distance is 100 times anything physicists could achieve before. According to The Guardian, Professor Wieslaw Krolikowski did not underestimate the achievement.
“Demonstration of a large scale laser beam like this is a kind of holy grail for laser physicists.”
The scientists theorize that their tractor beam could be used to remove pollution from the atmosphere or for manipulating tiny dangerous particles. It’s still a long ways from the science fiction dreams of enthusiasts, but it’s a start.
The full paper on the laser tractor beam can be found Nature Photonics.
[Image Credit: CBS/Star Trek: The Next Generation]