Extension of Linear-Velocity Margin in Phase Change Optical Recording with a Variable Pulse Compensation

Abstract

In the history of optical disks, two flavors of usages have been proposed and implemented. The one usage is for the Audio-Visual use, such as Mini Disk, Compact Disk (CD) and their family. The other usage is for computer peripherals, such as MO disk conformable to ISO standard. One significant difference in these two usages is characterized by the linear-velocity in reading and recording. The former media is used at a low linear-velocity of less than 10m/s and suitable for real-time operation. The latter is used at higher linear-velocity of more than 10m/s to achieve high data transfer rate. Phase change optical disk (PC disk), especially Ge-Sb-Te recording film 1-2), can be applied for both of these two usages. The PC disk has the following favorable features, 1-beam overwrite, simple optical system similar with the CD family. PC disk also has capability for higher density recording by Land and Groove recording3), PWM recording4), and the recording with shorter wavelength laser.5) However, the PC disk usually poor linear-velocity margin in conventional overwriting. The composition of the recording layer and film stacks must be carefully designed for each velocity with respect to crystallization speed and ability of amorphization.6) There has been no report that demonstrates an extension of applicable linear-velocity of a PC disk with a fixed active layer and film stacks. It is desirable for a fixed PC disk to cover such a wide linear-velocity range because the above mentioned two usages are merging in recent multimedia era.