Maarten Kuijper

Phase-Change Media for High-Numerical-Aperture and Blue-Wavelength Recording

We have studied the feasibility of doped eutectic SbTe alloys for practical application in digital video recording (DVR) rewritable phase-change media for high-numerical-aperture (NA=0.85) and blue-wavelength (λ=405 nm) recording. Remaining issues such as thermal cross-erase in land/groove recording and the thermal stability of recorded amorphous marks have been investigated and resolved. This work has resulted in the realisation of 22.5 GB phase-change media complying with the DVR blue format. The future of doped eutectic SbTe alloys in the phase-change recording-speed race is also promising, as the crystallisation speed and archival life stability can be optimised more or less independently by tuning the Sb/Te atomic ratio and adding Ge, respectively. We have demonstrated that a user data transfer rate of 70 Mbit/s (DVR double speed) is within reach using our current phase-change composition, and are expecting to realise data rates of over 100 Mbit/s in the near future.

Groove-only recording under DVR conditions

We developed a groove-only rewritable disc for the DVR system with a blue laser diode (wavelength 405 nm). Using standard detection electronics we obtained a capacity of 23.3 GB. Higher capacities are possible with advanced detection methods. Wide system margins are obtained at 320 nm track pitch and 80 nm channel-bit length. Fast-growth materials are used for the active layer. No thermal cross-write effect is present in the central track when neighboring tracks are repeatedly rewritten.

34 GB Multilevel-Enabled Rewritable System Using Blue Laser and High-Numeric Aperture Optics.

Multilevel (ML) technology increases storage capacity and data transfer rates of an optical data storage system. ML is shown to be a strong candidate for use with a high numeric aperture (NA) and blue-laser system by demonstrating good margin performance.

High-NA achromatic objective lens

Developed an achromatic high-NA objective making use of non-periodic phase structures. The effectiveness of the achromatic objective lens has been demonstrated in the BD recorder. No reduction of the recording quality due to laser wavelength shift could be observed. Due to the wide nature of the zones, the phase structure can directly be incorporated into the aspherical surface of the objective lens without significantly influencing the transmission of the objective, making it a cost effective way to make the objective achromatic.