Feeds

US nanotech boffins track evanescent light

By following the Poynting vector, of course

Business security measures using SSL

Researchers in the States have found a way of predicting how evanescent light waves might behave. The breakthrough could clear the way for a new generation of nanoscale optical devices, including solar thermal energy technologies.

When things get very small, nanoscale small, the rules all change and almost every assumption based on knowledge of the big world has to be checked and checked again. For example, from our experience with lasers we know that light travels in a nice straight line, right?

Wrong. Make the path the light has to travel down small enough, and the poor photons weave across it like so many drunken fools wheeling home from a pub. Sort of.

Specifically, we're talking about evanescent light, the light that is emitted when photons are radiated between two surfaces separated by a gap that is less than the wavelength of light. The light wave is interrupted and - until now - unpredictable evanescent waves are produced.

"Understanding the behaviour of light at this scale is the key to designing technologies to take advantage of the unique capabilities of this phenomenon," said Zhuomin Zhang, a lead researcher on the project and a professor in the Woodruff School of Mechanical Engineering.

"This discovery gives us the fundamental information to determine things like how far apart plates should be and what size they should be when designing a technology that uses nanoscale radiation heat transfer."

The team set out to track the evanescent waves by tracking the direction of the electromagnetic energy flow (a Poynting vector), rather then the direction of the photons themselves (which is unknowable, in physics terms). Even electrodynamics is different at the nanoscale, and the cornerstone of the research was working out what those differences are.

"We’re using classic electrodynamics to explain the behaviour of the waves, not quantum mechanics," Zhang said. "We’re predicting the energy propagation - and not the actual movement - of the photons."

Zhang explains that the team observed the light bending as the photons tunnelled through the vacuum separating the surfaces, just nanometres apart. The evanescent waves separated during this process, allowing the team to predict the energy path of the waves.

This information is vital to the construction of near-field thermophotovoltaic systems, nanoscale imaging based on thermal radiation scanning tunnelling microscopy and scanning photon-tunnelling microscopy, the researchers said. ®

Providing a secure and efficient Helpdesk

More from The Register

next story
PORTAL TO ELSEWHERE scried in small galaxy far, far away
Supermassive black hole dominates titchy star formation
Boffins say they've got Lithium batteries the wrong way around
Surprises at the nano-scale mean our ideas about how they charge could be all wrong
Bacon-related medical breakthrough wins Ig Nobel prize
Is there ANYTHING cured pork can't do?
Edge Research Lab to tackle chilly LOHAN's final test flight
Our US allies to probe potential Vulture 2 servo freeze
Europe prepares to INVADE comet: Rosetta landing site chosen
No word yet on whether backup site is labelled 'K'
Cracked it - Vulture 2 power podule fires servos for 4 HOURS
Pixhawk avionics juice issue sorted, onwards to Spaceport America
City hidden beneath England's Stonehenge had HUMAN ABATTOIR. And a pub
Boozed-up ancients drank beer before tearing corpses apart
prev story

Whitepapers

Providing a secure and efficient Helpdesk
A single remote control platform for user support is be key to providing an efficient helpdesk. Retain full control over the way in which screen and keystroke data is transmitted.
WIN a very cool portable ZX Spectrum
Win a one-off portable Spectrum built by legendary hardware hacker Ben Heck
Saudi Petroleum chooses Tegile storage solution
A storage solution that addresses company growth and performance for business-critical applications of caseware archive and search along with other key operational systems.
Protecting users from Firesheep and other Sidejacking attacks with SSL
Discussing the vulnerabilities inherent in Wi-Fi networks, and how using TLS/SSL for your entire site will assure security.
Security for virtualized datacentres
Legacy security solutions are inefficient due to the architectural differences between physical and virtual environments.