Feeds

Multi-color laser created by UCSB scientists

Excitons with extra zing could make networks sing

Choosing a cloud hosting partner with confidence

A group of University of California Santa Barbara researchers is touting a new technique to create multi-coloured lasers.

The coherent light of lasers is created by pumping a suitable material with energy. The energy is absorbed by electrons in the material, which move briefly to a higher-energy state; when they shed that energy, it is given off as a photon – with the wavelength of the light determined by the resonant characteristics of the material (a simplified description).

Lasers with multiple wavelengths are usually created by mixing the outputs of different devices, but the UCSB approach is different: they’re persuading the material they’re pumping to emit multiple wavelengths, by pumping it with both near-infrared and terahertz-frequency beams.

It works like this: the material – in this case, nanostructures of gallium arsenide – is pumped with lasers of different wavelengths. The near-infrared beam creates excitons (electron-hole) pairs in the material; in other words, pulling the electron completely out of its orbit instead of lifting it into a higher-energy orbit.

The electron, however, retains its attraction to the hole it came from – and this is where the university has added its “secret sauce”, a second, more powerful terahertz beam. As explained by UCSB physics professor Mark Sherwin in the university’s announcement:

“The very strong, low-frequency free electron laser beam rips the electron away from the hole and accelerates it. As the low-frequency field oscillates, it causes the electron to come careening back to the hole."

The electron has excess energy because it has been accelerated, the statement notes, and when it slams back into the hole, the recombined electron-hole pair emits photons at new frequencies.

Even better, from a practical standpoint: in their paper for Nature (of which Sherwin is a co-author), the researchers say they can optimize the spacing of the multiple wavelengths emitted by their multi-color laser.

If miniaturized, that would give the multi-color laser a home in optical communications, where wavelength-division multiplexing (WDM) expands the carrying capacity of networks by using different wavelengths to carry different data streams.

All such an application would need is to replace the building-sized free-electron laser in the UCSB’s Broida Hall (so large because it’s tunable as well as very powerful) with a transistor laser operating in the terahertz range, Sherwin said. “Now that we’ve seen this phenomenon, we can start doing the hard work of putting the pieces together on a chip.” ®

Internet Security Threat Report 2014

More from The Register

next story
Antarctic ice THICKER than first feared – penguin-bot boffins
Robo-sub scans freezing waters, rocks warming models
I'll be back (and forward): Hollywood's time travel tribulations
Quick, call the Time Cops to sort out this paradox!
Your PHONE is slowly KILLING YOU
Doctors find new Digitillnesses - 'text neck' and 'telepressure'
Reuse the Force, Luke: SpaceX's Elon Musk reveals X-WING designs
And a floating carrier for recyclable rockets
Britain's HUMAN DNA-strewing Moon mission rakes in £200k
3 days, and Kickstarter moves lander 37% nearer takeoff
Rosetta science team thinks Philae might come to life in the spring
And disclose the biggest surprise of Comet 67P
Bond villains lament as Wicked Lasers withdraw death ray
Want to arm that shark? Better get in there quick
prev story

Whitepapers

Free virtual appliance for wire data analytics
The ExtraHop Discovery Edition is a free virtual appliance will help you to discover the performance of your applications across the network, web, VDI, database, and storage tiers.
Getting started with customer-focused identity management
Learn why identity is a fundamental requirement to digital growth, and how without it there is no way to identify and engage customers in a meaningful way.
The total economic impact of Druva inSync
Examining the ROI enterprises may realize by implementing inSync, as they look to improve backup and recovery of endpoint data in a cost-effective manner.
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?
Website security in corporate America
Find out how you rank among other IT managers testing your website's vulnerabilities.