Chang-min Park

Random Signal Characteristics of Super Resolution Near Field Structure Read-Only Memory Disc

We report the random pattern signal characteristics of the super resolution near field structure (Super-RENS) disk in a red laser optical system. (Laser wavelength 659 nm, numerical aperture 0.6) We improved the carrier to noise ratio (CNR) characteristics and the low frequency noise by optimizing the layer design and the pit structure, which results in 53 dB CNR at 173 nm pit length. It is equivalent to 50 GB capacity if it is converted by Blu-ray Disc (BD) specification according to the ratio of beam size. We also improved the readout power margin and the stability greatly by introducing the thermal control layer. The eye pattern under phase locked loop (PLL) state could be obtained through equalization adjustment (EQ). Through above improvements, we obtain the bER of 4.6×10-4 at 50 GB level by using partial response maximum likelihood (PRML) method.

Phase Change Super Resolution near Field Structure ROM

We confirmed a super resolution phenomenon and a typical super resolution near field structure threshold phenomenon in a read only memory (ROM)-type sample disk. We found that this super resolution phenomenon originates from a phase-change layer and is closely related to the thermal properties of the super resolution layer. We also improved the readout stability using a co-sputtered layer with phase change (GST) and dielectric materials (ZnS-SiO2).

Optical Disc for Small Form Factor Optical Drive

We investigated the signal characteristics of a 46 mm small optical disk in a blue laser system [laser wavelength, 405 nm; numerical aperture (NA), 0.85]. To determine the physical dimensions of the rim area of the disk, we considered some factors affecting this rim area. We confirmed the transcription of the substrate, and the thickness of the cover layer of the disc. Also, by spin coating and selecting the optimum viscosity of the resin used for the 0.1-mm-thick cover layer, it was possible to reduce rim area from 1.5 mm to 1.0 mm. Also, we confirmed that the thickness of the substrate for sufficient mobility should be thicker than 0.5 mm.

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.

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.