Super storage

A new technology is set to boost the storage capacity of CD s by 1,000 times

Published: Saturday 30 November 1996

digital and analog information -- words, music, and pictures -- would no longer be limited to the surface of cd . Instead, they would be stored on hundreds of layers within it. The new cd s would use photons instead of electrons to acquire, transmit, store and process data. Researchers at the State University of New York, Buffalo,( ub ) impregnate cheap, clear plastics with light-sensitive dyes that can be turned on or off by an infra-red laser beam. In this process, called 'two-photon absorption', a molecule pumped with light of sufficiently high intensity absorbs two photons of light.

The presence of the dye enables the polymer to strongly absorb infra-red laser light due to the two-photon absorption, and this absorption can be confined to a very precise area by tightly focusing the laser beam, says Jayant Bhawalkar of the ub Photo Research Laboratory.

The absorbed light causes a tiny point of the dyed polymer to change properties, such as its colour of fluorescence. In an example of one mechanism for doing this, the spot where absorption occurs gets bleached, that is, the fluorescence is removed. This is the 'writing' process where bleached spots become the data that can be 'read' by an infra-red beam. This mechanism results in a 'write once/ read many times' operation. Other mechanisms can produce many reversible 'read/write' operations. The new technology permits digital-data storage and analog-image storage, enabling large quantities of pictures, photographs and other visual information to be collected.

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