Photonics: Beam me up

May 24, 2012 By Lee Swee Heng

'Tractor beams' of light that pull objects towards them are no longer science fiction. Haifeng Wang at the A*STAR Data Storage Institute and co-workers have now demonstrated how a tractor beam can in fact be realized on a small scale.

Tractor beams are a well-known concept in science fiction. These rays of light are often shown pulling objects towards an observer, seemingly violating the , and of course, such beams have yet to be realised in the real world. Haifeng Wang at the A*STAR Data Storage Institute and co-workers have now demonstrated how a tractor beam can in fact be realized on a small scale. “Our work demonstrates a tractor beam based only on a single laser to pull or push an object of interest toward the light source,” says Wang.

Based on pioneering work by Albert Einstein and Max Planck more than a hundred years ago, it is known that light carries momentum that pushes objects away. In addition, the intensity that varies across a laser beam can be used to push objects sideways, and for example can be used to move cells in biotechnology applications. Pulling an object towards an observer, however, has so far proven to be elusive. In 2011, researchers theoretically demonstrated a mechanism where light movement can be controlled using two opposing light beams — though technically, this differs from the idea behind a tractor beam.

Wang and co-workers have now studied the properties of lasers with a particular type of distribution of light intensity across the beam, or so-called Bessel beams. Usually, if a laser beam hits a small particle in its path, the light is scattered backwards, which in turn pushes the particle forward. What Wang and co-workers have now shown theoretically for Bessel beams is that for particles that are sufficiently small, the scatters off the particle in a forward direction, meaning that the particle itself is pulled backwards towards the observer. In other words, the behaviour of the particle is the direct opposite of the usual scenario. The size of the tractor beam force depends on parameters such as the electrical and magnetic properties of the particles.

Although the forces are not very large, such do have real applications, says Wang. “These beams are not very likely to pull a human or a car, as this would require a huge laser intensity that may damage the object,” says Wang. “However, they could manipulate biological cells because the force needed for these doesn’t have to be large.”

Such applications are the driving force for future experimental demonstrations of such pulling effects. The technology could, for example, be used to gauge the tensile strength of cells, which would be useful to investigate whether cells have been infected. “For instance, the malaria-infected blood cell is more rigid, and this technology would be an easy-to-use tool to measure this,” adds Wang.

Explore further: Nike krypton laser achieves spot in Guinness World Records

More information: Novitsky, A., et al. Single gradientless light beam drags particles as tractor beams. Physics Review Letters 107, 203601 (2011)

add to favorites email to friend print save as pdf

Related Stories

Tractor beams come to life

Sep 08, 2010

Tractor beams, energy rays that can move objects, are a science fiction mainstay. But now they are becoming a reality -- at least for moving very tiny objects.

NASA studying ways to make 'tractor beams' a reality

Oct 31, 2011

Tractor beams -- the ability to trap and move objects using laser light -- are the stuff of science fiction, but a team of NASA scientists has won funding to study the concept for remotely capturing planetary ...

Bend breakthrough sends light around a corner

Aug 12, 2011

(PhysOrg.com) -- Australian National University scientists have successfully bent light beams around an object on a two dimensional metal surface, opening the door to faster and cheaper computer chips working ...

Are electron tweezers possible? Apparently so

Nov 09, 2011

(PhysOrg.com) -- Not to pick up electrons, but tweezers made of electrons. A recent paper by researchers from the National Institute of Standards and Technology (NIST) and the University of Virginia (UVA) demonstrates that ...

Emerging from the vortex

Feb 17, 2012

Whether a car or a ball, the forces acting on a body moving in a straight line are very different to those acting on one moving in tight curves. This maxim also holds true at microscopic scales. As such, a ...

Recommended for you

New approach to form non-equilibrium structures

8 hours ago

Although most natural and synthetic processes prefer to settle into equilibrium—a state of unchanging balance without potential or energy—it is within the realm of non-equilibrium conditions where new possibilities lie. ...

Nike krypton laser achieves spot in Guinness World Records

10 hours ago

A set of experiments conducted on the Nike krypton fluoride (KrF) laser at the U.S. Naval Research Laboratory (NRL) nearly five years ago has, at long last, earned the coveted Guinness World Records title for achieving "Highest ...

Chemist develops X-ray vision for quality assurance

14 hours ago

It is seldom sufficient to read the declaration of contents if you need to know precisely what substances a product contains. In fact, to do this you need to be a highly skilled chemist or to have genuine ...

The future of ultrashort laser pulses

14 hours ago

Rapid advances in techniques for the creation of ultra-short laser pulses promise to boost our knowledge of electron motions to an unprecedented level.

IHEP in China has ambitions for Higgs factory

Jul 23, 2014

Who will lay claim to having the world's largest particle smasher?. Could China become the collider capital of the world? Questions tease answers, following a news story in Nature on Tuesday. Proposals for ...

User comments : 0