Shigeru Furumiya

Wobble-Address Format of the Blu-ray Disc

We explain a new address format that is adapted in the Blu-ray Disc Rewritable format. The address information is prerecorded by wobbling the groove track. It is based on a single tone carrier to obtain a stable and accurate write clock. The modulation scheme is a combination of minimum shift keying (MSK) that is strong for media noise and saw tooth wobble (STW) that is strong for wobble shift. The robustness of the format is demonstrated by measurement of the system margins.

Quadruple-Layer Write-Once Disk for Blue Laser Based on Te–O–Pd Recording Films

The excellent performance of a 100-GB-capacity write-once disk was demonstrated. The disk has quadruple recording layers, i.e., Layer 3, 2, 1, and 0 (from the laser-incident side of the disk) based on the 4× Blu-ray disc (BD) format. Each layer is provided with a phase-change type memory film of Te–O–Pd, whose thickness was 20 nm for Layer 0, and only 6 nm for Layers 1, 2, and 3 in order to obtain high transmissivity. Additionally, for Layers 2 and 3, a metallic reflection layer was not needed and an AlN film with high thermal conductivity was formed next to each recording film. The AlN film suppressed the heat-induced damage of thin recording films. Consequently, the high transmissivities of 64% (Layer 1), 75% (Layer 2), and 81% (Layer 3) were achieved so that a quadruple layer disk with high quality was realized. The experimental disk showed tolerance to a wide range of writing speeds from 1× (36 Mbps) to 4× (144 Mbps). Good jitter values for each layer within an available maximum laser power of 27 mW on the disk were demonstrated. The acceleration test for lifetime using the Arrhenius plots showed that this write-once disk has an estimated lifetime of more than 100 years at 30 °C and 85% relative humidity (RH).

Over-500-Mbps Data Recording on Write-Once Media with L-Shaped Write Strategy

We have confirmed the necessary conditions to achieve data recording at a channel bit rate of over 500 Mbps. We discuss the approaches and experiments adopted to realize such high-speed data recording by way of present available techniques. In order to clarify the necessary conditions for them, we have investigated the laser response speed required for recording, optimum write strategy and suitable media for high-speed mark formation. As a result of these studies, the over-500-Mbps data recording was realized by applying a new L-shaped write strategy with a laser pulse of 0.7 ns rising time to Te–O–Pd write-once media of the Blu-ray Disc format.

Practical study of saw-tooth wobble addressing by theoretical and experimental approaches

We have proposed a new concept of addressing in optical disks, the saw-tooth wobble (STW) groove. In this paper, the practical study of the STW by theoretical and experimental analyses is described. The address information corresponds to an even ordered-harmonic, so the write clock has no jitter factor. A 30 dB of carrier-to-noise ratio is sufficient for achieving 1E-2 of address error. Using a practical detection system, a radial tilt margin of more than ±0.6 degree is achieved.

Optical disk recording system of 25-GB capacity

A new in-groove format with Saw-Tooth wobble (STW) for blue laser and high NA system is proposed. The STW is designed in order to satisfy for high reliability of the addressing, continuous generation of system clock and easy linking of write data. The format efficiency is high, and moreover, it is confirmed capability for not only single-layer but also dual-layer phase change optical disk. In the conditions of the disk diameter of 120mm, track pitch of 0.32 micrometers and data bit length of 0.116micrometers /bit, the user capacity per layer is achieved 25G-bytes using D8-15 codec and PR(3443)ML channel. The bottom jitter of 9.4 percent by level-slice and the bit-error-rate of 6.0E-6 after PRML are obtained. In addition, the wide stress margins, as the radial/tangential tilt and the defocus tolerances, demonstrate to be enough to realize consumer optical disk systems of the next generation.

High-Density Recording on a Phase-Change Rewritable Disk using a 405 nm Blue Laser Diode

The possibility of a 28 GB capacity/layer has been studied using a blue laser diode and high-NA objective lens. Under the conditions of the disk diameter of 120 mm, cover layer thickness of 0.1 mm, track pitch of 0.32 µm and data bit length of 0.104 µm/bit, a low bit error rate (ber) of 10-5 was obtained in both modulations of D8-15 and RLL(1,7) with partial response maximum likelihood (PRML). A wide tilt margin comparable to that in the case of DVD-RAM was obtained in RLL(1,7).

Enhanced modulation of scattered light from phase-change nanoparticles by tailored plasmonic mirror image

We theoretically clarified a principle for the highly sensitive detection of a crystalline-amorphous transition in phase-change (PC) nanoparticles by tailoring the mirror image of localized surface plasmons in the crystalline phase. The difference of back scattering (DBS) can be greatly enhanced via the strong coupling of a PC nanostructure with the Ag nanoantenna by designing the dielectric structures around the PC nanoparticle. Remarkably, a DBS of 0.5% can be realized for 12 nm PC nanoparticles using conventional far-field measurements. The results shown here have potential applications in the nanoscale detection of temperature and pressure and for terabyte-class optical storage devices.

One-Head Near-Field Writing/Erasing on a Rewritable Dual-Layer Optical Disk Having High-Index Cover and Separation Layers

Near-field writing and erasing on a rewritable dual-layer optical disk with a single solid immersion lens (SIL) optical head is demonstrated for the first time. A novel beam expander enabled access to both information layers of the disk without exchanging two individual optical heads. A rewritable dual-layer disk having high-index (n=1.8) cover and separation layers was newly developed. By using the SIL optical system and the disk, an effective numerical aperture (NA) of 1.42 is achieved and a recording capacity of 180 Gbyte for the dual-layer rewritable disk is expected.

New Method of Calibrating Adaptive Writing Pulses for Digital Versatile Disc Random Access Memory (DVD-RAM) 4.7 GB Drive

In this paper, a new method of calibrating adaptive writing pulses suitable for installing into the digital versatile disc random access memory (DVD-RAM) 4.7 GB drive is described. To obtain a wider margin of write/read operation, it is desirable to optimize all adaptive parameters for every disk inserted into the drive. We propose the jitter minimizing (JM) method, which is characterized by using selected test patterns, detecting only jitter in the drive and applying a search algorithm to obtain bottom jitter. As a result of optimizing all parameters by JM, the total calibration time is 4.8 s with the accuracy of ≤1 ns, and overwrite jitter of random data is 8.6% at the drive. It is proved that JM offers the same results as the measurement by the time interval analyzer (TIA), uses small-sized hardware and exhibits satisfactory performance for application in commercial drives.

New Prml for Asymmetrical Signals in High-Density Optical Disks

The partial response maximum-likelihood (PRML) signal processing technique is effective for high-density recording media. However, asymmetry in the playback signal, which is caused not only by inter-symbol interference, but also by mismatched recording power in phase-change optical disks, markedly degrades the quality of PRML signal processing. In this paper, we propose an adaptive equalizer with a LMS algorithm for asymmetrical signals. We show the improved results in recording and playback experiments.