Bell Laboratories, no longer owned by AT&T Corp, but instead one of the proudest possessions of Lucent Technologies Inc, has by no means completely given up on optical computing technologies. Where two-dimensional diffraction gratings have been causing valuable optical effects for centuries, three researchers at the world famous Murray Hill, New Jersey lab announced in Nature that they have discovered a method to persuade billions of tiny glass spheres to order themselves into large three-dimensional arrays. Such three-dimensional diffraction gratings – using glass spheres of a diameter comparable with the wavelength of visible or infra- red light – could form the basis of optical filters, optical switches or more efficient lasers. The researchers say that by using a template it is possible to create bulk, hard-sphere crystals with a crystal structure, orientation and size that would not have been formed otherwise. Pierre Wiltzius and Rene Ruel from Bell Laboratories, and Alfons van Blaaderen, from Utrecht University in the Netherlands, allowed micron-sized silica particles suspended in a liquid settle slowly to the bottom of the vessel, where they formed a hexagonal pattern as would a large number of billiard or tennis balls under the same circumstances. To solve the alignment problem, the researchers induced the spheres to grow not in a hexagonal pattern, but in a square pattern, by creating a template with a series of holes that form the desired square pattern. The silica spheres that create the second layer settle into the indentations between four spheres in the first layer, and the spheres in the third layer settle directly over the spheres in the first layer. The result is a large single structure that is well-ordered in all three directions. There is no limit to the size of a device that can be created, the team says.
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