Overview and the future of phase-change optical disk technology

Phase-change optical disk technology in the early days dealt with three issues: cyclability, erase characteristics and sensitivity. These were resolved by materials development, and disk layer structure technologies. This paper shows the high (carrier to noise ratio) CIN recording characteristics of a multi-level phase-change optical disk. Multi-level mark radial width modulation (MRWM) recording experiments have demonstrated 4-level (level 0, level 1, level 2 and level 3) recording capability. Even level 1 marks with a radial width of 200 nm have a high C/N ratio of more than 50 dB. The laser pulse width and laser power assigned MRWM, M-level recording is expected the potential for marks storing density proportionally to log(2) M. This technology offers the feature of enhanced density and compatibility with a digital versatile disk (DVD) pick-up.