A new generation of super-light-sensitive compounds could make the internet and other optical networks faster, say researchers. The new class of carbon-based molecules interact with light more strongly than any tested before.
鈥淭hey can beat a barrier that people have been trying to break for 20 years,鈥� says chemist Koen Clays, from the Catholic University of Leuven, Belgium. 鈥淪ome people were afraid we would never do so.鈥�
The barrier 鈥� known as the 鈥淜uzyk gap鈥� 鈥� is the distance between the theoretical maximum light/matter interaction and that observed in reality. For the last two decades or so, the best performing molecules have achieved just one-thirtieth of the sensitivity of the theoretical maximum interaction.
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The new class of compounds interact with light 50% more strongly, and were developed by Yuxia Zhao at the Chinese Academy of Sciences, Beijing. Clays and colleague Xavier Perez-Moreno investigated their performance, while Mark Kuzyk from Washington State University, US, after whom the gap was named, has explained its basis.
Speed and light
The strength of the compounds鈥� interaction with light was measured by observing how much infrared laser light their molecules could scatter. More scattering means a stronger interaction. The measurements are made relative to reference compounds, so absolute figures cannot be applied. But the new compounds were 50% better than any before. That puts them at one-twentieth of the theoretical maximum interaction.
That could have implications for the internet and other networks that rely on optical signals, says Ivan Biaggio of Lehigh University, Pennsylvania, US. Compounds more sensitive to light can be used to make components to manipulate optical signals more efficiently and quickly.
鈥淚t may help the community to finally deliver the optical switching performances that are needed for tomorrow鈥檚 data-processing networks,鈥� he says. Components that translate electrical into optical signals, process them, and change them back into electrical ones currently use inorganic materials like silicon-based semiconductors.
If all the components in a network used compounds like Zhao鈥檚 鈥渋t would be orders of magnitude faster鈥�, says Clays.
Bumpy bridge
The new molecules are more sensitive because Zhao tried a new design strategy, Clays explains. Like previous sensitivity record-holders, they have a group of atoms at one end that donate electrons to a group at the other when passing light waves disturb electrons in the molecule.
鈥淯ntil now people thought it was best to make a smooth 鈥榖ridge鈥� of only carbon atoms between the two ends,鈥� explains Clays. Yet Zhao鈥檚 molecules have a 鈥渂ump鈥� made from non-carbon atoms built in to the carbon bridge.
Quantum calculations show that such bumps can enhance the interaction with light. The atoms in the bump constrain the waveforms of the electrons in the carbon bridge. That prevents those electrons from interfering with each other and makes them more sensitive to the effect of light waves. Adding more bumps may produce compounds even closer to the theoretical maximum, says Clays.
Journal reference: Optics Letters (vol 32, p 59)
