Yoon-Gi Kim

Experimental Results of Space Layer Thickness for Blue-Wavelength Dual-Layered Disc

To determine the effects of spherical aberration due to defocus and interference of layer 0(L0) and layer 1(L1) in high-density dual layered-discs, 17 sets of discs structures are measured while maintaining thickness uniformity of the space layer within ±1.5 µm for one revolution. After measuring the discs, an optimum thickness of 30 µm of the space layer is obtained.

Experimental Results of 3-piece 0.4 mm Molded Substrate

To achieve the same margin as that of the digital versatile disk (DVD), using a 0.4 mm substrate has been molded for a high-density optical disk for double-sided dual layer disk. In this paper, the characteristics of a read-only and rewritable high-density optical disk of 0.4 mm plastic substrate is reported using a new resin material for injection molding, to improve both the birefringence and the mechanical characteristics.

A Feasibility Study of Writing Compensation for Tangential Tilt

For achieving a higher density than that of current digital versatile discs(DVD), a high numerical aperture(NA) and blue wavelength light source is tested to increase the areal density. In contrast to this positive effect, the coma aberration is doubled with a NA of 0.65 and wavelength of 400 nm compared to that of the current rewritable DVD at the same disc tilt. Additionally, the effective power density for recording is much smaller than that in the case of a DVD with a tilt. In this paper an efficient compensation method for disc tilt will be presented.

THERMALLY OPTIMUM STRUCTURE FOR OVERWRITING CYCLABILITY AND CROSS-ERASE CHARACTERISTICS

As two key restrictions for increasing the recording capacity, cross-erase and jitter from narrowing track pitch (0.55 µm–0.6 µm) and making small marks (0.40 µm–0.62 µm) are presented using a thermally optimum phase-change optical disk with the ability of thermal endurance and high thermal conduction as well as minimum crosstalk and maximum groove signals. For overwriting jitter no increase after 104 cycles is observed. The cross erase after 104 overwriting cycles resulted in less than 1% of jitter increase from the initial value.

Effect of first information layer on second information layer in dual-layer disc

For a dual layer structure, the effect of different physical geometries is studied using 0.65 and 0.85 of numerical aperture(NA), and this result gives an incitation for making a physical format for rewritable high density disc.

Optical Storage System for 0.4 mm Substrate Media Using 405 nm Laser Diode and Numerical Aperture 0.60/0.65 Objective Lens

The most important application of the blue-laser optical storage system is the recording high-definition digital broadcasting. For this application, the next-generation blue laser optical storage system requires a data capacity of at least 2 h of a digital broadcasting data stream with a data transfer rate of 23.5 megabits per second (Mbps). In addition to the capacity goal, system compatibility with the conventional digital versatile disc (DVD) system as well as the compact disc (CD) system is important. In order to satisfy the requirements of blue-laser optical storage, a system for media with a substrates thickness of 0.4 mm was proposed, and improved molding technology, crosstalk cancellation technology, dynamic tilt compensation technology and quadrature phase shift keying (QPSK) modulated wobble addressing method were developed for the system. We confirm the feasibility of the proposed system for media with a 0.4 mm substrate using a 405 nm blue laser diode and objective lens with a numerical aperture (NA) of 0.6 (0.65 for rewritable system).

High-density magneto-optical disk suitable for short wavelength recording

High density magneto-optical recording was realized with the combination of a compact green laser and a very sensitive NdTbFeCo/TbFeCo MO disk for the wavelength of 532 nm. This media has a high Kerr rotation angle at 532 nm and maintains a stable recording domain. With an objective lens of 0.6 NA, CNR of 48 dB and jitter of 3.0 nsec by mark edge recording was obtained for a mark length of 0.45 micrometers (0.34 micrometers /bit) at a writing power of 4.5 mW.