August 22, 2005

Marvels of the Day: Taming Light, Nanotube Sheets

Filed under: Marvels — Tom @ 2:15 pm

Every once in a while, it’s good to step back and marvel with childlike awe at amazing technological breakthroughs when they occur. This is one of those days. Two items that caught my attention not only have awesome potential to change the world for the better, but it looks like their potential can be realized pretty quickly, not decades from now.

Click “more” to learn more:

First, what appears to be the successful taming of light (HT Myopic Zeal; bolds are mine) holds near-term potential for collosal improvements in telecom and other areas (perhaps the next few iterations of Moore’s Law?):

A team of researchers from the Ecole Polytechnique Fédérale de Lausanne (EPFL) has successfully demonstrated, for the first time, that it is possible to control the speed of light — both slowing it down and speeding it up — in an optical fiber, using off-the-shelf instrumentation in normal environmental conditions. Their results, to be published in the August 22 issue of Applied Physics Letters, could have implications that range from optical computing to the fiber-optic telecommunications industry.

On the screen, a small pulse shifts back and forth — just a little bit. But this seemingly unremarkable phenomenon could have profound technological consequences. It represents the success of Luc Thévenaz and his fellow researchers in the Nanophotonics and Metrology laboratory at EPFL in controlling the speed of light in a simple optical fiber. They were able not only to slow light down by a factor of three from its well-established speed of 300 million meters per second in a vacuum, but they’ve also accomplished the considerable feat of speeding it up — making light go faster than the speed of light.

This is not the first time that scientists have tweaked the speed of a light signal. Even light passing through a window or water is slowed down a fraction as it travels through the medium. In fact, in the right conditions, scientists have been able to slow light down to the speed of a bicycle, or even stop it altogether. In 2003, a group from the University of Rochester made an important advance by slowing down a light signal in a room-temperature solid. But all these methods depend on special media such as cold gases or crystalline solids, and they only work at certain well-defined wavelengths. With the publication of their new method, the EPFL team, made up of Luc Thévenaz, Miguel Gonzaléz Herraez and Kwang-Yong Song, has raised the bar higher still. Their all-optical technique to slow light works in off-the-shelf optical fibers, without requiring costly experimental set-ups or special media. They can easily tune the speed of the light signal, thus achieving a wide range of delays.

“This has the enormous advantage of being a simple, inexpensive procedure that works at any wavelength, notably at wavelengths used in telecommunications,” explains Thévenaz.

Second, Mainstream applications for nanotechnology appear to be gaining steam. The trick, as with many scientific breakthroughs, has been figuring out how to get from the lab to cost-justified production. One example of where the crossover to the practical appears to have been made is with nanontube sheets (HT James Hudnall; bolds mine):

Nanotube sheets come of age
Clear, conductive sheets produced at high speed.
They’re soft, strong, and very, very long.

Large, transparent sheets of carbon nanotubes can now be produced at lightning speed. The new technique should allow the nanotubes to be used in commercial devices from heated car windows to flexible television screens.

“Rarely is a processing advance so elegantly simple that rapid commercialization seems possible,” says Ray Baughman, a chemist from the University of Texas at Dallas, whose team unveils the ribbon in this week’s Science1.

Nanotubes are tiny cylinders of carbon atoms measuring just billionths of a metre across. They are light, strong, and conductive. But for years their promise has outweighed their utility, because the complicated processes involved in making devices from nanotubes were too slow and expensive to be used in large-scale manufacturing.

But now, nanotubes have gone into warp drive. Baughman’s team can churn out up to ten metres of nanoribbon every minute, as easily as pulling a strip of sticky tape from a reel. This ribbon can be up to five centimetres wide, and after a simple wash in ethanol compacts to just 50 nanometres thick, making it 2,000 times thinner than a piece of paper.

The ribbons are transparent, flexible, and conduct electricity. Weight for weight, they are stronger than steel sheets, yet a square kilometre of the material would weigh only 30 kilograms. “This is basically a new material,” says Baughman.


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