CD-rewritable and future disc technology

In the Optical Data Storage Conference in 1995, the basic concept of CD-Rewritable (CD-RW), which was formerly called CD-Erasable, and the disc technology with the Ag-In-Sb-Te phase change material was presented. In that paper, some important features that had been considered strongly desirable for a rewritable CD system were listed, and since then the solutions for these items have been standardized or implemented as the CD-RW system. These features are: compatible with existing computer systems and software; erasable with direct overwrite (DOW); recordable using CD-R recorders with minimum modification; readable on CD-ROM players with minimum modification; and reliable. The same topics based on disc technology, such as optimum power control (OPC) principle or reliability, are discussed in this paper. Another advantage, readability at short wavelength, has also been realized by simple optimization ofthe layer structure. The dependency of the reflectance of a CD-RW disc on the wavelength is shown. The reflectance has little sensitivity for the wavelength in the range that covers both the CD and Digital Video Disc (DVD) systems. This feature would enhance the CD-RW´s potential as the sole practical recordable/rewritable media to bridge between the existing CD world and the emerging DVD world.