Sony Puts Blue-Green Laser to Work

Sony has announced an optical disc recording system that employs a blue laser for high-density data storage.
The 12-GB model uses a 515-nm blue-green laser unveiled by Sony in January 1996. A high-NA (0.85) lens focuses the beam on a 12-cm optical disc, where it records or reads a 0.1-mm phase-change layer. The phase-change material is a germanium antimony tellurium alloy that crys- tallizes and decrystallizes to record and erase the data.
Sony was able to achieve 4.5 hours of recording time at a total transfer rate of 6 Mb/s, which meets industry standards for high-quality television products.