Number 191 (Story #3), August 23, 1994 by Phillip F. Schewe and Ben Stein A DIGITAL HOLOGRAPHIC STORAGE SYSTEM , one actually integrated with a computer hard drive, has been developed by scientists at Stanford. In such a system data is converted into light patterns. The light waves enter a photorefractive medium, where they bring about microscopic rearrangements of electric charge which in turn affect the local index of refraction. To read out the data, a reference laser beam is sent into the medium; the refracted beam, bearing the decoded data, is detected with a charge-coupled device. Data can be stacked up in the hologram by recording at several angles. By home-computer standards, the Stanford results so far are modest: total storage capacity of 163 kB and a data transfer rate of 6.3 MB per second. The researchers believe future hologram performance should be much better: terabytes of storage and transfers above 1 gigabit per second. (John F. Heanue, Matthew C. Bashaw, Lambertus Hesselink, Science, 5 August.)