Roel Van Woudenberg

Optical Disc System for Digital Video Recording

We have developed a new error correction method (Picket: a combination of a long distance code (LDC) and a burst indicator subcode (BIS)), a new channel modulation scheme (17PP, or (1, 7) RLL parity preserve (PP)-prohibit repeated minimum transition runlength (RMTR) in full), and a new address format (zoned constant angular velocity (ZCAV) with headers and wobble, and practically constant linear density) for a digital video recording system (DVR) using a phase change disc with 9.2 GB capacity with the use of a red (λ=650 nm) laser and an objective lens with a numerical aperture (NA) of 0.85 in combination with a thin cover layer. Despite its high density, this new format is highly reliable and efficient. When extended for use with blue-violet (λ≈405 nm) diode lasers, the format is well suited to be the basis of a third-generation optical recording system with over 22 GB capacity on a single layer of a 12-cm-diameter disc.

Trends in optical recording

Optical recording technology is evolving rapidly, driven by the demands of higher storage capacities and increasing data rates. In this contribution, we discuss the technology roadmap of optical disc recording. The emphasis will be on rewritable optical recording, in particular, phase change recording.

High Data-Rate Phase-Change Media for the Digital Video Recording System

The digital video recording (DVR) system combines a high numerical aperture (NA=0.85) with a thin cover layer to achieve higher storage capacities in optical recording. In addition to capacity, the data-rate is a key parameter for DVR and a major challenge in research on phase-change materials. Using Ge2Sb2Te5 as the phase-change material, we demonstrate recording using a red laser diode (λ=650 nm) at a user data-rate of 33 Mbps and a capacity of 9.2 GB for a single layer disc of 12 cm diameter, i.e. completely satisfying all the DVR system requirements. In addition, we achieved data-rates of up to 50 Mbps by applying a different stack design. Furthermore, we extend DVR to the blue-violet wavelength region. Using a GaN laser diode (λ=400 nm) in our recording set up, a capacity of 21.5 GB was achieved at a data-rate of 28 Mbps.

Format Description and Evaluation of the 22.5 GB Digital-Video-Recording Disc

We describe the format of the 22.5 GB rewritable digital-video-recording (DVR) system. The format is based on an objective lens with a high numerical aperture (NA=0.85), a thin cover layer (0.100 mm thick), and a blue-laser diode (λ=405 nm). We discuss experimental verification of the format and possible future extensions. The DVR system is well suited to be the basis of a third-generation optical-recording family for high-definition video recording.

SHORT WAVELENGTH PHASE-CHANGE RECORDING

We discuss phase-change recording at blue wavelengths at densities corresponding to that of a (read-only) digital versatile disk (DVD), and beyond. We demonstrate in-groove recording on a 0.60-mm-thick, 120-mm-diameter disk with a capacity of 6 Gbyte, achieved with a wavelength of 488 nm and a numerical aperture of 0.60. We discuss our results in relation with recently standardized rewritable phase-change disks for red wavelength and the implications for systems at even shorter wavelengths.