In the computer revolution, the optical disk is poised to be the all-purpose storage medium of choice. But before it can fulfill this heady role, it will have to store a whole lot more information than it does today.
Nowadays the zeros and ones of digital information are carved into the surface of a plastic disk as a string of microscopic marks and spaces. As the disk spins under a laser beam, the beam, if it encounters a space, reflects off a shiny aluminum backing behind the semitransparent plastic and triggers a photodetector. When the beam encounters a mark, on the other hand, it scatters. Hal Rosen, a staff member at IBM’s Research Division in San Jose, California, woke up one morning with a simple but powerful idea that builds on this technology. Rosen thought of layering marks and spaces. First he removed the aluminum backing. The plastic still reflected ...