First we heard about the possibility of working warp drives, and now we’ve heard news that physicists have demonstrated a working tractor beam in the lab. It’s not quite as impressive as what we’ve seen on the USS Enterprise, but it is a step in the right direction. Physicists David Ruffner and David Grier constructed an optical beam that pulled a 30 micrometer silica sphere suspended in water, just like fictional tractor beams pull spaceships into docking bays. Although Bessel beams have been known to exist for years, this is the first time they’ve actually been used to pull an object back. From io9:
So, in an effort to create this ‘optical conveyor,’ Ruffner and Grier adjusted the periodic intensity of the Bessel beam’s axis so that it could optically trap the micrometer silica sphere. Then, by changing the beam’s relative phase, the trapped object was selectively moved both upstream and downstream along the conveyor. Unlike previous (failed) experiments, they were able to do this by multiple lenses that could slightly bend the beams and cause them to overlap — what caused a strobe effect behind the particle, which provided the required energy to draw the object back towards the source.
The possibility of combining multiple beams to move an object in three dimensions was also put forth, but the scalability of the process is questionable. It would currently require a tremendous amount of energy that might actually destroy the object that is being pulled in—but with additional research they might just find an energy source that would allow them to move larger objects.
(via Physical Review Letters)