This all began when we were trying to do something completely different with the materials," said John Fourkas, a chemistry professor who led the research at Boston College's Eugene F. Merkert Chemistry Center. "It was by accident." The researchers used a laser set at a specific intensity and focal range to write information digitally in layers by causing a chemical change in the material.

When the same laser was set at a lower intensity and fired at the same area, the material gave off a fluorescent glow indicating readable data was present. Lasers used on standard DVDs and compact discs read pits either engraved on the surface by another laser or stamped in mass production.

With the Fourkas-led team's discovery, in the area known as 3D optical-data storage, the changed material is transparent when not hit directly by the lower-intensity laser. That lets the laser focus on different levels in the material to write and read digital data, Fourkas said. So, far, researchers have been able to write data on as many as 25 levels, he said in an interview.

"We don't yet know how this happens, exactly," Fourkas said. The materials that the team used are stable, and the data don't degrade after repeated readings by the low-intensity laser.