New Materials Made By Blending Plastic, Dye Store 1,000 Times More Data Than Conventional Cds

ORLANDO -- New, polymer-based photonic materials into which can be packed "stacks" of data, like pages in a book, have been developed by University at Buffalo scientists.

Made of extremely inexpensive plastic blended with new dyes designed at UB, the materials store thousands of times more data than conventional compact disks (CDs).

The UB researchers also have developed an optical technology -- similar to that used in CD players -- to "read" the new materials.

The new materials and technology -- the combination of which allows for extremely compact data storage and easy read/write access -- were described for the first time today (Aug. 27) at the national meeting of the American Chemical Society.

While current compact disks store information only on their surfaces, "these new materials could revolutionize data storage because they allow data to be stored in the depth of a disk," said Paras N. Prasad, Ph.D., professor of chemistry, director of the UB Photonics Research Laboratory and principal investigator.

Other members of the research team are Jayant D. Bhawalkar, Ph.D.; Ping-Chin Cheng, Ph.D.; Ryszard Burzynski, Ph.D.; Deepak Kumar, Ph.D.; Gary Ruland; Shan-Jen Pan, Ang W. Shih, Wendy C. Chang, Wen-Shan Liou and Mun-Soo Park. The new materials they developed are capable of storing up to 1 terabyte of data per cubic centimeter -- one thousand times more than can be stored in a conventional CD.

"You would have to stack more than 1,000 conventional CDs one on top of the other in order to get the same amount of data that is in 1 cubic centimeter of one of these new materials," explained Bhawalkar, UB research assistant professor in the Photonics Research Laboratory.

In his presentation here, Prasad showed a video illustrating the new technique and how a confocal microscope probing deep into the material can "read" each frame of a Bugs Bunny cartoon. Several seconds of the cartoon are stored in stacks of data in a cubic volume, each side of which has the thickness of a human hair.

According to Prasad, this may be the first time frames of a movie have been stored in a stacked format and reproduced in a three-dimensional, data-storage medium. The method also will make it possible to store efficiently color movies, which require three times as much storage space as black-and-white images.

At the heart of the new materials is a phenomenon called two-photon absorption, in which a molecule absorbs two photons of light simultaneously if pumped with light of sufficiently high intensity.

Until now, most materials have been capable only of a very weak absorption of two photons, making them inadequate for most applications. Novel dyes developed by the UB researchers and exhibiting strong two-photon absorption, as well as strong fluorescence emission, are blended with transparent plastics to make the data storage medium.

"The presence of the dye enables the polymer to strongly absorb infrared laser light due to two-photon absorption and this absorption can be confined to a very precise area by tightly focusing the laser beam," said Bhawalkar. The absorption of light causes the material at the focal point to change properties, such as its color or fluorescence emission; this corresponds to the "writing" process.

Because the infrared beam penetrates deep into the material, data can be stored in its bulk, as opposed to only on its surface as in current CD technology.

"Now it is possible to penetrate optically the depth of the disk and access any given spot in it precisely, because the two-photon absorption occurs only at that spot," said P.C. Cheng, Ph.D., professor of electrical and computer engineering and the director of the Advanced Microscopy and Imaging Laboratories at UB.

"In one example, the spot where absorption occurs gets bleached, thus reducing the fluorescence emission from that spot," he explained. The presence or absence of bleached spots then becomes the data that is "read." Prasad demonstrated the utility of the material, using a confocal microscope equipped with a pulsed laser to "write" several stacks of data inside a polymer disk. The laser beam that "writes" digital data and images within the polymer block is controlled by a computer interface and software developed by the UB researchers.

In addition to digital data stored in conventional CDs, the two-photon materials permit storage of analog images, making the material ideal for archiving very large quantities of pictures, photographs and other visual information that are inefficient to store on today's CDs.