High-density Digital Versatile Disc Research Articles

Nanoscale lithography with visible light: optical nonlinear saturable absorption effect induced nanobump pattern structures

Industrial approaches to improve lithographic resolution usually rely upon short-wavelength laser or charged particles of even shorter wavelengths. However, nanoscale lithography with visible light is more effective for practical applications because of its low cost, easy operation, and so on. In the current work, a technical scheme for the optical nonlinear saturable absorption effect to induce nanobump pattern structures is proposed. The theoretical simulation indicates that the spot size can be squeezed and reduced to about 1/12 the original spot size using Si thin films as a nonlinear saturable absorption material, and GaN semiconductor diode as the laser source. The high-density digital versatile disk tester was used as the direct laser writing apparatus to verify the technical scheme. Nanostructures with a size of ∼80 nm were obtained. This size is ∼1/10 the spot size at optical diffraction limit.

Nano-optical information storage induced by the nonlinear saturable absorption effect

Nano-optical information storage is very important in meeting information technology requirements. However, obtaining nanometric optical information recording marks by the traditional optical method is difficult due to diffraction limit restrictions. In the current work, the nonlinear saturable absorption effect is used to generate a subwavelength optical spot and to induce nano-optical information recording and readout. Experimental results indicate that information marks below 100 nm are successfully recorded and read out by a high-density digital versatile disk dynamic testing system with a laser wavelength of 405 nm and a numerical aperture of 0.65. The minimum marks of 60 nm are realized, which is only about 1/12 of the diffraction-limited theoretical focusing spot. This physical scheme is very useful in promoting the development of optical information storage in the nanoscale field.

Optical Head Using Single Objective Lens for Four Types of Optical Disks

An optical head using a single objective lens for Blu-ray disc (BD), high-density digital versatile disc (HD DVD), digital versatile disc (DVD), and compact disc (CD) has been developed, which is suitable for high-speed recording and reading. A relay lens unit, which consists of two convex lenses and one concave lens, corrects the spherical aberration and realizes high light power efficiency for each disk. A numerical aperture (NA) control element, which contains a liquid crystal aperture and a wavelength selective aperture, controls the NA of the objective lens for each disk. A coma aberration caused by the objective lens shift is detected based on differential phase detection signals for read-only disks and push–pull signals for recordable or rewritable disks, and is corrected by moving one of the lenses in the relay lens unit by an actuator. A diffraction-limited focused spot and good readout signal characteristics were obtained for each disk, and the validity of this optical design has been demonstrated.

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.

The Design of an Integrated Pick-Up Head for High-Density Digital Versatile Disk, Digital Versatile Disk and Compact Disk

A novel design of triple-wavelength design for a compact optical pickup head is presented here. We propose the use of two rhomboid beam-splitter prisms for HD-DVD, DVD and CD devices to align signals with three different wavelengths on the same optical axis. The light is collimated by a collimating lens. The parallel beams are incident on the wavelength selector. The wavelength selector separates the wavelengths with different numerical apertures. The different wavelength signals are focused on the disc by an objective lens.

A study on UV-curable coatings for HD-DVD: Primer and top coats

This study relates to the development of coatings for optical discs in high-density digital versatile disc systems (HD-DVD or blue lay disk) that use a high numerical aperture of 0.85 at 405 nm wavelength and have a protective top layer over a primer layer for protection against damage and dust. Ultraviolet-curable raw materials of two acrylic monofunctional monomers ( isobornylacrylate, IBA and tetrahydrofurfurylacrylate, THFA) and two kinds of urethaneacrylate oligomers (OUMD and OUME) have been easily mixed with photoinitiators. Curing rate of these materials was characterized by FT-IR. In case of top coats, VTES (vinyltriethoxysilane) and acrylic acid were added to enhance the abrasion resistance. These two kinds of UV-curable resinous materials having no solvent were synthesized and investigated as means for making a blue ray disk having good optical and mechanical properties. In addition, dynamic characteristics including reflectivity, fluctuation of RF signal and noise level were also investigated.

Integration of Photonic Detectors in Standard SiGe HBT BiCMOS

The currently emerging optical data storage technologies of Blu-Ray Disk, respectively High Density Digital Versatile Disk (HDDVD), have opened a new field of activity for photodetectors preferentially integrated in a SiGe heterojunction transistor (HBT) BiCMOS process platform. Besides the advantages this process offers for analog signal processing we show how HBT process modules can be used to integrate fast, high-responsivity photodetectors sensitive to blue, red and near-infrared light of wavelengths 405, 660 and 785nm, respectively. The tradeoffs made for tuning HBT performance are discussed with respect to their impact on photodiode performance. The integration of the photodetector can be carried out with layout changes only not altering any other process step making it therefore an easy-to-do and free- of-extra-cost extension of the HBT BiCMOS base process.

Triple-wavelength optical pickup head designs for compact disk, digital versatile disk and high-density digital versatile disk devices

We present a triple-wavelength design for a compact optical pickup head which uses two rhomboid prisms in parallel with three laser diodes. The design can be used for compact disk, digital versatile disk and high-density digital versatile disk devices. The specific prism lens used decreases the geometrical size and reduces the total number of optical components. The trade-off between tolerance and fabrication is also presented.

Feasibility of High-to-Low Design for Advanced Rewritable High-Density Digital Versatile Disc

The low-to-high reflective design has been widely adopted for the by advanced rewritable high-density digital versatile disc (HD DVD-ARW). Current DVD discs are all of high-to-low reflective design; therefore, we believe that this design can be utilized for the HD DVD-ARW disc. This note shows the structure of a high-to-low reflective design for a HD DVD-ARW. It indicates that the crystalline reflectivity is greater than the amorphous reflectivity. In order to achieve high-to-low reflective design, an optical simulation and sample test have been performed, including the design of the thickness of each layer, the measuring of reflectivity and modulation, and an eye-pattern test. The feasibility of the high-to-low HD DVD-ARW disc is successfully demonstrated.

Synthesis and Characteristics of Protective Coating on Thin Cover Layer for High Density-Digital Versatile Disc

This study relates to the optical disc used in the high-density digital versatile disc (HD-DVD) system that uses a high numerical aperture of 0.85 at 405 nm wavelength. The disc has a protective layer formed on the light-incident surface for protection against damage and dust. The synthesis of the UV-curable resinous material, as means of making a protective layer within sufficient margins of thickness variation and optical and mechanical properties, was investigated. In addition, the dynamic characteristics, including reflectivity, fluctuation of the RF signal and noise level, were also investigated.

Block and Codeword Interleaving Scheme for the High Density Digital Versatile Disc

The effect of noises from smaller dusts and scratches is higher than the conventional optical storage systems, e.g., compact disc(CD) or digital versatile disc(DVD) by the higher numerical aperture (NA=0.85) and thin cover layer (0.1 mm) of the high density DVD. Accordingly, new error correcting code (ECC) is needed to correct not only both short burst errors and random errors but also long burst errors. So, the interleaving scheme between two ECC blocks is considered to improve the error correction capability. In this paper, we will show our new block and codeword interleaving scheme (BCIS) and calculate the block error rate of BCIS after error correcting by probability method under the error model of Sony's burst error distribution and compare with the conventional reed-solomon product code(RSPC) of DVD.

An Advanced Signal Detection Technique for Digital Versatile Disc Systems

We compare various signal detection techniques for high-density digital versatile disc (DVD) systems in terms of performance and hardware complexity, and propose a fixed-delay trellis search with decision feedback (FDTrS/DF) suitable for ASIC chip implementation. Based on various simulation and implementation results, it is shown that the proposed FDTrS/DF provides the best performance among various signal detection techniques, such as partial response maximum likelihood (PRML), decision feedback equalizer (DFE), fixed-delay tree search with decision feedback (FDTS/DF), and signal space detection with decision feedback (SSD/DF), even with low hardware complexity.

Byte Merging Inter-Row Interleaving Scheme for the Error Control of High-Density Digital Versatile Disk

An efficient interleaving scheme, named byte merged inter-row interleaving (BMIRI) for an error correction code (ECC) block in the higher density digital versatile disk-random access memory (DVD-RAM) is presented. The error correction performance with the BMIRI has been investigated by computer simulations for various long burst and short burst errors. The results show that the BMIRI is effective for ECC block of higher density DVD-RAM.

Dual thermal and UV-curable powder coatings

This study relates to the development of coatings for optical discs in high-density digital versatile disc systems (HD-DVD or blue lay disk) that use a high numerical aperture of 0.85 at 405 nm wavelength and have a protective top layer over a primer layer for protection against damage and dust. Ultraviolet-curable raw materials of two acrylic monofunctional monomers ( isobornylacrylate, IBA and tetrahydrofurfurylacrylate, THFA) and two kinds of urethaneacrylate oligomers (OUMD and OUME) have been easily mixed with photoinitiators. Curing rate of these materials was characterized by FT-IR. In case of top coats, VTES (vinyltriethoxysilane) and acrylic acid were added to enhance the abrasion resistance. These two kinds of UV-curable resinous materials having no solvent were synthesized and investigated as means for making a blue ray disk having good optical and mechanical properties. In addition, dynamic characteristics including reflectivity, fluctuation of RF signal and noise level were also investigated.

Exposure Method Using Photoresist Mask for High-Density Optical Disk Mastering

A high-density digital versatile disk (HD-DVD) is being developed, aiming for high definition television. It is thought that the capacity of HD-DVD would be 15 GB, for example when its track pitch is 0.42 µm, its minimum mark length must be 0.22 µm. To fabricate such a high-density optical disk, we develop an exposure method using a photoresist mask. Super-resolution is also studied in order to make the exposure beam diameter smaller.