A team of physicists has developed a laser-based system that can record data 1000 times faster than any previous holographic device and retrieve the information with just 1% of the errors. The technology, described in today's issue of Science*, is a long way from your neighborhood computer store. But other researchers say it is an important step toward making a reality of holographic data storage, which can pack vast amounts of data into a three-dimensional (3D) storage material.
Holographic data storage uses a pair of lasers to ionize the atoms of light-sensitive crystals. The two beams--one a "reference" beam and one containing data--create an interference pattern in the crystal, translating the data signal into a 3D hologram. The hologram is imprinted on the material, as electrons released by the excited atoms in the bright regions of the interference pattern migrate to darker regions, setting up electric fields that wrinkle the crystal lattice. One limit to the technology has been the speed of the electron at which the electrons migrate, which compounds into significant delays.
Now, a research team from SRI international in Menlo Park, California, reports that they have been able to improve both the speed and accuracy of holographic data storage. Instead of ionizing the atoms in the crystal, computer scientist Ravinder Kachru and his colleagues use extremely well-tuned lasers to excite electrons to a higher energy level, without kicking them completely off the atoms. (These energy levels can persist for hours in certain materials, the researchers say, and possibly days at extremely low temperatures.) The recording process is much faster, since it requires no physical movement of electrons. The team used the system to record an image of Albert Einstein, and with the help of an improved computer algorithm that interprets the stored data, they were able to retrieve an identical image, without any apparent errors.
The demonstration is "a nice piece of work," says data storage researcher Michael Jefferson of IBM Almaden Research Center, in San Jose, California. Although the technology is "not ready for prime time," he says the latest improvements bring holographic data storage closer to being a legitimate contender in competition to handle the data-storage demands of future generations of computers.