January 4th, 2007
New molecules for a faster Internet
An international team of researchers has discovered a new generation of optical molecules which interact 50% more strongly with light than any molecules ever tested. These organic molecules, known as chromophores, have been theorized by physicists at Washington State University, synthesized by chemists in China and tested for their actual optical properties by chemists in Belgium. But if they're excellent candidates for being used in optical technologies such as optical switches and Internet connections, these new materials should not be used before several years — if ever.
As the Washington State University (WSU) news release reminds us, optical technologies have been investigated for almost 40 years now. And a WSU physicist, Mark Kuzyk, who's working at the Laboratory for Nonlinear Optical Studies, discovered in 1999 "a fundamental limit to how strongly light can interact with matter."
Here is how Mark Kuzyk describes what is known as the Kuzyk Limit. In fact, he prefers the term it prefers the term 'fundamental limit.' "The limit isn’t a single number; it’s a curve on a graph that shows how strongly any given kind of matter can interact with light. The notion that light and matter 'interact' might sound odd to a layman. To a physicist, it opens a whole spectrum of possibilities." Here is a picture of Kuzyk describing this limit (Credit: Robert Hubner, for WSU). As he explains, "Because it's so simple, it had to be fundamental. There's some beauty in the equations."
For more information about the Kuzyk Limit, you can read "Taking it to the limit" (Cherie Winner, Washington State Magazine, May 2006), from which the above image has been extracted.
But things have changed and Kusyk now thinks this limit can be broken.
Earlier this year Kuzyk and two WSU colleagues published theoretical guidelines describing molecular structures that should excel at interacting with light. Koen Clays, a chemist at the University of Leuven in Belgium, had pioneered the use of a test called hyper-Rayleigh scattering to measure the strength of a molecule's light interaction.
Working on seven molecules provided by Yuxia Zhao at the Chinese Academy of Sciences, Clays and his team "found that two of them showed a more powerful interaction with light than had ever been observed before." So what is new with these molecules?
In the new designs, each molecule has a component at one end that donates an electron and a component at the other end that accepts an electron. In between is the "bridge" portion of the molecule. Previous efforts to boost the interaction with light focused on "smoothing out" the bridge to allow electrons to flow more easily from donor to acceptor end.
Now the researchers are starting to synthesize more molecules with similar properties. If they succeed to embed them into thin films or optical fibers, this will mean faster connections for all of us. But right now, these molecules are just in labs.
Anyway, if you want to know more about these molecules, the latest research work about them has been published by Optics Letters under the name "Modulated conjugation as a means for attaining a record high intrinsic hyperpolarizability" (Vol. 32, Issue 1, Pages 59-61, January 1, 2007). Here are two links to the abstract and to the full paper, thanks to arXiv.org.
Sources: Washington State University news release, January 2, 2007; and various websites
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