Off topic. but I just found this so interesting. Madd Maxx- -----Original Message----- From: R. J. Tavel, JD [mailto:[EMAIL PROTECTED]] Sent: Thursday, July 12, 2001 6:50 AM To: Learning Electronically About Freedom mailing service Subject: WHAT'S NEXT: Through the Looking Glass, to Holographic Data Storage http://www.nytimes.com/2001/07/12/technology/circuits/12NEXT.html STORAGE space is tight these days, and not just in cramped New York apartments. Home dwellers anywhere might be delighted to stow the 10 years' worth of receipts, canceled checks and tax records clogging their files in a space no bigger than an ice cube. Hospitals, insurance companies, banks and department stores might also appreciate storage that compact for their vast databases. Now two researchers from Canada and Spain have devised a glass-based material that they say may one day safely store huge amounts of data in just such small spaces. The new, glassy medium is not magnetic, like the hard drive in a computer, but holographic. Holography is an optical process that stores not only three-dimensional images like the familiar ones found on credit cards and CD packages but the 0's and 1's of digital data as well. Because the data can be recorded and retrieved at hundreds of angles within a storage material rather than just on the surface, page after page can be stored on material an inch thick. But although the space-saving advantages of holography have been known for four decades, manufacturers have not been able to produce an affordable holographic data storage system. "We have had no commercial product, mainly for the lack of a good storage medium," said Prof. Glenn T. Sincerbox, director of the Optical Data Storage Center at the University of Arizona in Tucson. The new material may change all that, offering the possibility of practical holographic read-only storage for the first time. The new medium, basically a glass matrix shot through with tiny holes, was devised by Dr. Mar�a Luisa Calvo, chairman of the optics department at Complutense University in Madrid, and Pavel Cheben, a scientist at Optemia Inc., a new photonics company in Ottawa. The material is based on the inventors' adaptation of an old-fashioned way of making glass called the sol-gel method. In this process, glass is created not by melting sand at high temperatures and letting it cool, but by working with liquid precursors to the glass at room temperature. Dr. Cheben said that the method made it possible to add the photosensitive chemicals critical for holography without their being destroyed as they would be by the high temperatures used in conventional glass preparation. "The ingot of glass appears to be solid, but there are small holes within," Dr. Cheben said. "These holes are filled with liquid acrylic and the photo-initiator we added." In the researchers' experiments, the mixture of glass and photosensitive chemicals was poured into vials and left to dry for 10 days. "The material can be made into any shape, but it was easier in these early experiments to work with one- to two-centimeter discs," said Dr. Cheben. After 10 days the material was polished and then put through the holographic process. In a conventional hologram of an object, a fine-resolution photosensitive film is exposed to a laser beam that has been split in two. One of the beams is reflected off the object while the other travels unimpeded to the film. The light waves from the two sources interfere with each other, and the image of the object is recorded in this interference pattern. In the holographic storage experiments, a simpler interference pattern, of light and dark stripes, was recorded onto the photosensitive material in the glass. (Once the hologram is recorded it cannot be erased, which is why the medium is intended for write-once, read-many-times applications.) So far, Dr. Cheben said, the glass-based material has retained the imprinted information perfectly for a year. The glass backbone of the storage system offers certain advantages over the plastic polymer matrixes that are currently being developed for holographic storage. These plastic materials tend to shrink during the process, corrupting the data. The new glass structures remain rigid. "The key problem with polymeric matrixes for holographic storage," said Dr. Sincerbox, "is that they tend to get thinner during the process." The new material controls shrinkage to far less than 1 percent, he said. The glassy material lends itself to production in thick slabs, significant because the thicker the holographic material, the more information it can store. Typical thicknesses range from half a millimeter to five millimeters. The test will be how the material performs when the laser beams are not ordinary ones, as they were in the experiments reported by the authors, but are actually bearing data. To carry data, one of the beams would have a pattern imposed on it: either an image, or a checkerboard of light and dark squares representing 1's and 0's. "They will need to put information in the beam, record it, read it out, and determine the bit error rate," Dr. Sincerbox said. "That's the true test if the material will work for holographic storage." Dr. David A. Waldman, vice president for research and development at Aprilis Inc. in Cambridge, Mass., said that recording a hologram with the new material would require expensive lasers consuming a great deal of energy. Aprilis is developing a holographic storage system that includes a polymer-, not glass-based, medium that can be used with a low-intensity, less expensive laser. Dr. Waldman acknowledged that the glass matrix was more stable in its dimensions. "But there are still many problems with this material," he said � primarily, a low sensitivity to the laser light. But Dr. Cheben said that the sensitivity problem was not a big one. "Our sensitivity is slightly lower than the norm because of the thickness of our material," he said. The thinner materials are slightly more sensitive, he said, but the tradeoff is reduced storage density. The new material, Dr. Cheben said, can be modified as it is developed and tested. "Developers can easily play with and adjust the sensitivity of the medium," he said. "What's important is that this is a new family of materials." Please let us stay on topic and be civil. To unsubscribe please go to http://groups.yahoo.com/group/cia-drugs -Home Page- www.cia-drugs.org OM Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
