Feeds

NYU boffins demo tiny tractor beam

To beam the impossible beam

Beginner's guide to SSL certificates

While using light pressure to move something in the same direction as light is well-understood, using beams to pull objects is a bit more difficult.

Now, a couple of Davids from New York University – Ruffner and Grier, respectively – have demonstrated just that. In a paper published in Physical Review Letters, and available in full at David Ruffner’s research page here, they claim to have demonstrated a tractor beam that can move an object either towards or away from the light source, “without the aid of outside forces”.

A beam called a Bessel beam is at the heart of the demonstration. Bessel beams direct light in concentric circles around a single dot, and this gives the beams an interesting property: they reform after passing an obstacle. In mathematics, if not in real life, such beams could propagate forever, because they don’t suffer the diffraction that scatters ordinary lasers.

The way that Bessel beams reform behind a (small) obstruction has already made them useful for optical tweezers, but Ruffner and Grier found that a single beam couldn’t be sufficiently tuned to act as a tractor.

To create the “tractor beam”, the researchers added a second Bessel beam, and then varied the relative phase of the two beams. This makes the optical trap created in the beams move – and the trapped particle moves with the trap, “allowing bi-directional transport in three dimensions”, they write.

As New Scientist explains, the interaction of the two Bessel beams creates an alternating pattern of bright and dark regions. With the right tuning, photons in the bright regions scatter back towards the light source, creating a pico-scale light pressure that pushes a particle in the beam towards the next bright region.

The demonstration by Ruffner and Grier is not, however, ready to trap the Starship Enterprise: they demonstrated its effectiveness by moving microscopic spheres of silica, suspended in water, over distances of 30 micrometers. ®

Bootnote: This is, by the way, different from optical tweezers, which already exist. They can move micro-scale objects in two dimensions, but don’t exert a noticeable pull towards the beam source. ®

Secure remote control for conventional and virtual desktops

More from The Register

next story
Antarctic ice THICKER than first feared – penguin-bot boffins
Robo-sub scans freezing waters, rocks warming models
Your PHONE is slowly KILLING YOU
Doctors find new Digitillnesses - 'text neck' and 'telepressure'
SEX BEAST SEALS may be egging each other on to ATTACK PENGUINS
Boffin: 'I think the behaviour is increasing in frequency'
Reuse the Force, Luke: SpaceX's Elon Musk reveals X-WING designs
And a floating carrier for recyclable rockets
The next big thing in medical science: POO TRANSPLANTS
Your brother's gonna die, kid, unless we can give him your, well ...
NASA launches new climate model at SC14
75 days of supercomputing later ...
Britain's HUMAN DNA-strewing Moon mission rakes in £200k
3 days, and Kickstarter moves lander 37% nearer takeoff
prev story

Whitepapers

Seattle children’s accelerates Citrix login times by 500% with cross-tier insight
Seattle Children’s is a leading research hospital with a large and growing Citrix XenDesktop deployment. See how they used ExtraHop to accelerate launch times.
Why CIOs should rethink endpoint data protection in the age of mobility
Assessing trends in data protection, specifically with respect to mobile devices, BYOD, and remote employees.
A strategic approach to identity relationship management
ForgeRock commissioned Forrester to evaluate companies’ IAM practices and requirements when it comes to customer-facing scenarios versus employee-facing ones.
High Performance for All
While HPC is not new, it has traditionally been seen as a specialist area – is it now geared up to meet more mainstream requirements?
Protecting against web application threats using SSL
SSL encryption can protect server‐to‐server communications, client devices, cloud resources, and other endpoints in order to help prevent the risk of data loss and losing customer trust.