Self-Sharpening Effect of Phase Change Erasable Media

The characteristics of single-beam one-pass overwrite of SbTeGe phase change erasable (PCE) optical disks have been studied from a drive design point of view. In the recording process, an amorphous mark surrounded by a crystal ring (erase state) is recorded.The amorphous mark always has a clear edge even if erasability is relatively low in the low erase power area. We call this phenomenon the self-sharpening effect (SSE) which gives several advantages to the performance and design of the drive. SSE realizes wide power tolerance in a practical drive, which results in excellent interchangeability in terms of write/erase laser power. SSE also achieves a good off-track performance of less than +/- 0.1 µm of the optical beam and enables pulse edge recording even if overwrite erasability is relatively low.