3-D Photonic Crystals Sought

Photonic crystals, which contain properties that give butterfly wings their shimmering colors, are being used to revolutionize the future of telecommunications by making systems smaller, faster and more efficient.

By the end of a three-year European Sixth Framework Programme project dubbed NewTon, a team of European researchers hope to have developed the first functional telecommunication components using 3-D photonic crystals, the first step toward a long-term goal of developing a communications technology based entirely on transmitting information by light waves.

The crystals use light to transmit information many times faster than electricity, which is used today to transmit information over optical fibers through network nodes to the end user. While optical fibers also use light to transmit information, currently there is no competitive, compact, all-optical routing processor available.

The European team includes researchers from BASF Aktiengesellschaft, Hanover Laser Center, Thales Aerospace Div., Photon Design Ltd., the Technical University of Denmark and the Ecole Nationale Supérieure des Télécommunications de Bretagne. Half of the project is being funded by the European Union. The team is developing a photonic crystal capable of reflecting only single colors of the white light depending on the observation angle. Naturally occurring photonic crystals make butterfly wings vibrantly colorful, and assist with thermal management.

"A structured three-dimensional photonic crystal could be the key component for a compact optical semiconductor or even for an all-optical routing processor," said Reinhold J. Leyrer, PhD, who is BASF’s project leader in the Polymer Research division. "Converting optical signals into electrical signals would then be superfluous."

The first challenge for the scientists is the development of a stable, structured 3-D photonic crystal based on aqueous dispersions. These dispersions contain spherical polymer particles measuring about 200 nanometers that, depending on the chemical structure, can arrange themselves into a regular lattice, forming a crystal.

The scientists will have to enlarge the polymer particles contained in the dispersions to 1000 nm so their diameters are all exactly the same. Using emulsion polymerization, they also apply an additional structure measuring less than 20 nm onto the polystyrene particles to make the most stable, large volume 3-D crystal they can. Once they have the desired structure, one of the team partners will introduce "defects" into it.

Light at certain wavelengths then travels along these defects and even around sharp corners. The photonic crystal then acts as a photoconductor and takes the control over the propagation of light. The resulting structured crystal lattice would then be used as a template for manufacturing.

The spaces between the polymer spherical particles in the crystal lattice would be filled with silicon, and then the researchers will "burn" the polymer particles out of the lattice. The result is a stable structure that is a mirror image of the original crystal. Crystals of this type could be used as components for an all-optical routing processor in telecommunications.

Manufacturers of components for telecommunication systems would benefit most from the use of photonic crystals. Since the crystals are smaller than electronic components, equipment would also become increasingly smaller and cheaper while simultaneously offering improved performance. Components and equipment based on photonic crystals would also be more resistant and less vulnerable to electromagnetic radiation, the scientists said.

Devices made using the crystals could also have applications in the instrumentation market as chemical and biological sensors, and in the aerospace and security industries.

For more information, visit: www.projectnewton.com