Storing data in 1,000 points of light.
Wn chemist Tuan Vo-Dinh of Oak Ridge (Tenn.) National Laboratory began work on a new soil analysis system for the Environmental Protection Agency, he had no idea that the underlying principle, known as Raman scattering, held potential for an innovative optical data storage technology.
Typical compact disks store a binary code of ones and zeros as microscopic pits and valleys. A detector distinguishes laser light reflected from the contrasting surface features. Vo-Dinh now proposes an alternative storage approach, which he calls surface-enhanced Raman optical data storage (SERODS).
In the 1920s, physicist C.V. Raman discovered that the wavelengths of some of the light scattering from certain molecules differ from the wavelength of the light source, and that these differences carry information about the molecules' structures and abundances. Later, scientists observed that placing molecules close to certain surfaces such as silver enhances the Raman scattering effect, which otherwise is extremely subtle and difficult to detect. Extrapolating from his design of a soil analysis system using the enhanced effect, Vo-Dinh came up with the novel data storage approach. By coating a disk material such as silicon oxide with a film of silver and then with a layer of Raman-active molecules, Vo-Dinh can use a fine laser beam to induce specific microregions of the disk to produce distinctive Raman signals that serve as identifiable data bits. In a working SERODS system, ones and zeros would correspond to altered and unaltered microregions of the disk, respectively. Vo-Dinh's rough calculations predict that an optimized 12-inch SERODS disk could store 1 trillion letters -- well over 100,000 years' worth of SCIENCE NEWS.
Preliminary tests show that no more than 1,000 molecules are needed to represent 1 data bit, says M. Guven Yalcintas, director of technology transfer at Oak Ridge. But turning this concept into a working device will take long-term commitments by many companies, he adds.
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|Title Annotation:||optical data storage technology|
|Date:||Jan 6, 1990|
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