Write-once Optical Disk Research Articles

Microstructure and recording mechanism of Bi–Fe–(N) layer for high-density write-once optical disk

Bi–Fe–(N) thin film as the recording layer of high density digital versatile disk recordable optical disk was developed. For the disk sample with optimized layer structure, maximum partial response signal to noise ratio of 21.1 and minimum simulated bit error rate of 5×10−7 were achieved at the write power=5.7mW. Transmission electron microscopy characterization illustrated that the separation of Bi and Fe elements to form the coarse granular structure in the mark regime during laser irradiation comprised of the recording mechanism.

Diffusion and crystallization mechanisms of Ge∕Au bilayer media for write-once optical disk

Ge ∕ Au bilayer thin films were fabricated by magnetron sputtering method, the temperature dependence of resistance from room temperature to 500°C and concentration depth profiles are measured. From the temperature dependence of resistance measurement, we found two phase change phenomena which occurred at 175 and 360°C. The element concentration depth profiles of the as-deposited and recorded region indicate that the Au–Ge alloy is initially formed at the Ge∕Au interface. The dominant diffusion element is Au atom and the diffusion path is from Au layer to Ge layer. The optimum simulated bit error rate value is about 1.4×0−6 at 9.0mW under two time high definition digital versatile disk (HD DVD) recording speed. The dynamic tests show that this Ge∕Au bilayer films can be applied to one to two times HD DVD-R.

Dual-Speed Inorganic Write-Once Disk with Low-to-High Polarity

We have developed a new inorganic write-once optical disk for an optical recording system with a numerical aperture of 0.85 and a 405 nm blue-violet laser diode. The recording layer is composed of multi-layered structure of alternating Mg-based alloy layer and Si layer. Our experimental results showed that the recording sensitivity of the optical disk is strongly dependent on the stack structure of the recording layer, which can be optimized through adjusting the number of the component layers. Dynamic experiment results showed that the write-once optical disk has a low-to-high polarity and jitter value below 7.5% can be achieved at both 1× and 2× speeds. Effects of the multi-layered recording layer structure and the low-to-high polarity on recording performance are discussed.

Microstructure and recording mechanism of Ge∕Au bilayer media for write-once optical disc

The recording mechanism of Ge∕Au bilayer and its dynamic tests for write-once blue laser high density DVD (HD DVD) are investigated. It is found that Ge2Au3 phase is nucleated between amorphous Ge and crystalline Au layer after room temperature deposition. Crystallization of Ge∕Au interface layer at 170–190°C is induced by the nucleated Ge2Au3 sites at the interface, the bilayer structure is further heated to 200–450°C. After heating above 320°C, crystallized Ge are segregated at the grain boundary. The dynamic test results show that this Ge∕Au bilayer films can be applied to 1×–2× HD DVD-R.

New Write-Once Medium with NiOx Film Using Blue Laser

Both a new write-once medium with a sputtered NiOx film and a write-once optical disk using a blue laser has been fabricated. The optical constant of sputtered NiOx films for different ratios of O2/Ar was determined, and showed little dependence on sputtering ratios of O2/Ar and wavelength. The X-ray photoelectron spectra (XPS) data indicated those films have two major components, NiO and Ni2O3. Most NiOx films released oxygen gradually below 300°C. Over 300°C, there was an apparent transition due to the decomposition of the Ni2O3. At a writing power of 12 mW and a reading power of 0.5 mW under conditions of a numerical aperature (NA) of 0.65 and a wavelength of 405 nm, the carrier to noise ratio (CNR) was more than 47 dB and jitter was less than 13%. The recording principle depends primarily on the explosive pressure of the O2 released due to laser heating of the NiOx film.

Performance of a write-once multilayer optical disk that uses transparent recording material with an optical switching layer

A volumetric optical disk that has multiple transparent films with optical switching layers is used as a recording medium to increase the number of recording layers. In the disk the optical switching layer is adapted to reduce decay of laser energy and increase reading and recording sensitivity. Well-defined marks of approximately 100-nm depth can be placed precisely on the transparent films by a focused laser beam. Writing and reading of a four-layer recordable disk, fabricated by molding and spin bonding, have been demonstrated experimentally. The volumetric disk can achieve a high recording capacity with conventional optical pickups.

Comparison of access methods for time-evolving data

This paper compares different indexing techniques proposed for supporting efficient access to temporal data. The comparison is based on a collection of important performance criteria, including the space consumed, update processing, and query time for representative queries. The comparison is based on worst-case analysis, hence no assumptions on data distribution or query frequencies are made. When a number of methods have the same asymptotic worst-case behavior, features in the methods that affect average case behavior are discussed. Additional criteria examined are the pagination of an index, the ability to cluster related data together, and the ability to efficiently separate old from current data (so that larger archival storage media such as write-once optical disks can be used). The purpose of the paper is to identify the difficult problems in accessing temporal data and describe how the different methods aim to solve them. A general lower bound for answering basic temporal queries is also introduced.

Silver-gold compound metal island films for durablewrite-once optical disk memories

Silver-gold compound metal island (CMI) films fabricated by using a two-step evaporation method have been investigated for write-once (WO) optical disk memories. It has been experimentally confirmed that the CMI films are more durable than conventional silver island films reported as potential compact disc-compatible WO memories in previous work. In addition, the reflectance of the CMI film is as high as that of the silver island film at 800 nm and can be significantly reduced by heating the films at 150–200°C. This suggests that the silver-gold CMI films may be useful as write-once optical data storage media.

A coding approach for detection of tampering in write-once optical disks

We present coding methods for protecting against tampering of write-once optical disks, which turns them into a secure digital medium for applications where critical information must be stored in a way that prevents or allows detection of an attempt at falsification. Our method involves adding a small amount of redundancy to a modulated sector of data. This extra redundancy is not used for normal operation, but can be used for determining, say, as a testimony in court, that a disk has not been tampered with.

Challenges for tertiary storage in multimedia servers

The low cost per Mbyte of optical disk and magnetic tape storage makes these technologies particularly attractive for use in large capacity storage servers, including multimedia servers. However, these devices have performance problems that range from high costs for many optical drives to low performance and lack of random access in tape drives. We evaluate the performance on multimedia applications of several tertiary storage systems, including optical disk jukeboxes, arrays of optical drives, and storage hierarchies composed of magnetic disk arrays and magnetic tape libraries. We conclude that striped arrays of next-generation write-once optical disks will offer the best performance at acceptable cost.

Compact-disc compatible wideband write-once opticaldisc memories using multilayered ultra-thin silver films

A write-once (WO) optical disc memory with compact disc (CD) compatibility is demonstrated by using a multilayer consisting of a silver reflective layer, thin glass spacing layer, and silver quasi-island recording layer. The reflectance of the multilayer is >70% at a wavelength of 800 nm. The reflectance can be greatly lowered by laser irradiation, since the silver quasi-island layer changes by heating, becoming absorptive and of low reflectivity due to structural change. As a large reflectance change has been observed not only at 800 nm for CD but also at 650 nm for a digital video disc (DVD), a CD-DVD compatible wideband write-once optical disc is realised.

Write-once optical data storage media with large reflectance change with metal-island films

Gold (Au), silver (Ag), copper (Cu), and aluminum (Al) island films have been investigated for write-once optical data storage media with the high reflectance and the large reflectance changes induced by laser irradiation. We show that, of the four, the Ag and the Cu island films are the most useful as WO media at 800 nm. The Al island films are useful for a shorter wavelength region. The optical and structural changes in laser-written regions on the island films have also been investigated experimentally. It appears that the metal-island films show great potential as optical data storage media for compact-disk-compatible write-once optical disks.

Durable write-once optical disk memories for 800nmusing silver island films

Durable write-once (WO) optical disk media have been demonstrated by using silver island films with a protection layer of fluorine-contained polymers. The reflectance of the silver island films is high at the wavelength of 800 nm and can be greatly lowered by laser irradiation, owing to the thermal deformation of the islands. Laser writing has been experimentally confirmed at almost the same line speed as that of compact discs (CDs). Therefore it is expected that a CD-compatible write-once optical disc can be realised.

Write-once optical disk system measuring 300 mm using high-density, pit-edge recording

To meet the requirement for a second-generation digital optical disk with a larger capacity and a higher speed, the new 300-mm, write-once optical disk system described here uses pit-edge recording and the modified-constant-angular-velocity method [Maeda et al., Trans. IEICE E74, 951 (1991)]. New techniques that can use these methods together and are suitable for interchangeability-data composition and independent detection of the leading and trailing edges-have resulted in the most reliable data-storage system ever produced, we believe. The concept of this system, the characteristics of the new techniques, and the optimization of system performance are described.

Sn-Sb-Se/Sb-Bi Bilayer Phase-Change Media for High-Density Write-Once Optical Recording

We have developed Sn-Sb-Se/Sb-Bi bi-layer phase-change media for high-density write-once optical disks. Crystallized marks as small as 0.5 µ m are stably recorded without initialization. These phase-change media, compared to ablative type write-once media, have high carrier-to-noise ratio, low jitter, and long life. Mark-edge recording with multi-pulse laser irradiation on the media provides a linear bit density of 0.48 µ m/ bit and track pitch of 1.2 µ m using a 690-nm-wavelength laser diode and 0.55 numerical aperture (NA) objective lens. This corresponds to 1.1 Gbit/in.2, or 14 GB formatted data capacity per both sides for a 12-inch-diameter disk with a zoned constant angular velocity (ZCAV) format.

High density write-once optical disk for high definition television

The authors have developed a high density write-once optical disk using the reflection plane shift recording method. A high carrier-to-noise ratio (60 dB at 12.5 MHz) was obtained by using a 670-nm wavelength laser diode, which is enough to realize high-definition pictures of good quality. A high SNR (42 dB) of recorded HDTV (high-definition television) MUSE signals was obtained. This disk has format compatibility to Hi-Vision VD (video disk). It can also accommodate compressed digital HDTV signals.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Write-once optical disc media with large change of reflectance using copper island films

A new write-once optical disc medium using a metal island film is proposed and investigated experimentally. The reflectance and absorbance of an 8 nm thick copper island film were 49 and 37%, respectively, at a wavelength of 780 nm and the reflectance was decreased to 15% by heating the film at a temperature above 130 o C, which shows that it can be used as an efficient heat-mode write-once memory for commercially available laser diodes

Practical mini-PACS based on a hybrid video and digital network

The Department of Radiology of the Shinshu University Hospital is presently in the process of developing a new type of mini-PACS with a hybrid architecture consisting of a video and a digital image archiving network. The video block consists of a server station with a video write-once optical disk (LD) and three workstations which are connected to two ultrasound imaging devices and an MRI device. The video images from any of these imaging devices are transferred immediately onto an LD. The examiner can observe the archived images immediately without any interruption of the examination. The image transmission time, including the record and play-back, is within 3 s. The digital block consists of a personal computer server and various workstations linked to the ETHERNET. This digital system supports database management, and archives digital images. This prototype system was used for daily clinical examinations from February 1989 to January 1990 and 31 366 images from 1561 patients were stored on the video disk. This one year experience suggests that a hybrid mini-PACS system is practical for total image archiving when the image matrix is less than 512 × 512 and selected digital image archiving.

A checkpointing page store for write-once optical disk

A model paging system is described for write-once optical disk. The paging system checkpoints pages on a nonerasable, failure-resistant medium as a side effect of virtual memory operation. Most pages are already checkpointed at any given time. It is practicable to checkpoint the global state periodically by forcing the write-out of pages that have been modified since their last checkpoint, together with the page tables. The proposed checkpointing algorithm was simulated to evaluate the performance of paging and checkpoint to write-once optical disk. There are plausible values for the operating parameters that make the overhead of checkpointing negligible compared to paging. The lifetime of 1-GB write-once optical disk media used for paging and checkpointing can range up to three months under plausible operating conditions.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Simulative and analytical studies on performances in large multimedia databases

This paper summarizes the results of simulative and analytical studies on performances concerning the architecture of multimedia databases on large magnetic and optical data storage, suitable for multimedia document managment in the office environment. After the description of the relations of the multimedia database scheme and an outline of the main algorithms, evaluations on the storage occupation and on the average response time are worked out, depending on some macroscopic parameters of the multimedia database, in particular on the distribution of image segments on the write-once optical disks.