Katsusuke Shimazaki

Collimated Light Source Using Patterned Organic Light-Emitting Diodes and Microlens

We developed for the first time a collimated organic light-emitting diode (OLED) light source using a patterned OLED and a microlens. The structure of the collimated OLED light source was designed by conventional ray-tracking simulation. We demonstrated that the collimated OLED light source enhanced the luminance of a liquid crystal display (LCD) with a low aperture ratio by a factor of more than two compared with a conventional OLED light source, which was not patterned. The collimated OLED light source with the patterned OLED and microlens is thus very effective for achieving a highly efficient LCD with OLED backlight.

Magneto-Optical Disk Structure with High Write/Erase Repeatability

Over 107 write/erase repeatability has been achieved in magneto-optical (MO) disk by optimizing thermo-structural design through thermal conduction analyses. By combining this technology with that for anti-corrosion measures, a highly reliable and durable 5 1/4 inch MO disk has been developed. Carrier level degradation through write/erase repetition, which was observed in the cource of the development, is thought to be interpreted as a structure relaxation by annealing leading to a localized change in magnetic properties.

Exchange coupling effect of in-plane magnetized layer capped on TbFeCo

Abstract The mechanism of the capping layer effect of the reduction of switching field by the insertion of a PtCo layer directly coupled to the TbFeCo layer of a MO disk has already been investigated. It is supposed herein that the magnetization of the capping layer easily rotates to the direction of magnetic field, and subsequently helps the transition metal site magnetic moment of TbFeCo align parallel to the field through exchange interaction, while suppressing the nucleation of the microdomains, whose magnetization is anti-parallel to the field, in the interior of the laser-written mark.

New magnetic domain expansion MO phenomena using an in-plane magnetizing layer

For higher density MO recording, a magnetic domain expansion readout method named MAMMOS has been proposed. Herein we report a novel MAMMOS scheme using an in-plane to perpendicular magnetization changing effect. Expansion readout has been achieved by both a magnetic field modulation method and a light intensity modulation method. A clearly amplified readout signal was reproduced from repetition of 0.2 /spl mu/m packed marks.

Direct overwriting capability of magnetic multivalued MO media

As one of the most promising schemes for high density MO recording, a new media for magnetic multivalued recording has been proposed. By switching the external field on four levels, the quadri-valued signal was obtained. On the MMV media, field sensitivity is improved by controlling composition of PtCo capping layer coupled to TbFeCo. The external filed for recording four levels is reduced down to 350 Oe and direct overwriting capability is confirmed on 0.8micrometers mark length recording.

Low-density parity check code concatenated with generalized partial response equalizer for high-capacity magneto-optic recording channels

In this study, we investigate the application of advanced coding and signal processing techniques for a magneto-optical (MO) disk system in order to improve its recording capacity. In particular, we study the application of low-density parity check (LDPC) codes with iterative soft decoding to the center aperture detection magneto-optical (CAD-MO) recording channel. The channel pulse response is identified from the read-back signals using the least mean squares (LMS) algorithm. The minimum mean-squared error (MMSE) technique was used to design appropriate generalized partial response (GPR) targets. LDPC encoded data are written onto and digitized read back signals are collected from a spin stand. Off-line numerical evaluations show that LDPC code concatenated with a channel detector matched to the GPR target can increase the capacity.

Highly field sensitive (150 Oe) quadri-valued magnetooptical media for high-speed overwriting

For high-density and high-speed magnetooptical (MO) recording, the use of magnetic multi-valued (MMV) MO media has been proposed. [rf:1] A quadri-valued recording has been achieved using this media and a field modulation recording method. For practical use of this media, it is important to reduce the critical magnetic field to minimize the applied field for realizing the quadri-valued recording. We have achieved reduction of the critical magnetic field down to 150 Oe using a new coupled film, TbFeCo/GdTbFeCo.

Write/Erase Cyclability of TbFeCo for Mark-Edge Recording

Write/erase cyclability for mark-edge recording is studied using rare-earth element[RE]-rich TbFeCo media. Mark-edge jitter for the (1-7) random pattern is small enough even after millions of cycles of data writing and erasing.

Write/erase cyclability of TbFeCo for mark edge recording

Domain size changes due to thermal relaxation after high laser power irradiation on amorphous TbFeCo films were studied. In order to achieve mark edge recording for high‐density magneto‐optical memory, accurate domain size recording is required even after a million erase/write cycles. Highly accelerated erase/write test was performed on typical recording media, rare‐earth (RE) ‐rich and transition‐metal (TM) ‐rich disks. The elongation of the domain size written on the TM‐rich film after erase/write cycles was clearly evident; however, the change in the domain size of RE‐rich films was small. The small domain size change of the RE‐rich disk can be explained in terms of the rapid increase in the coercive force with decreasing temperature and the smaller domain‐wall driving force at recording temperature than those for the TM‐rich disk, even though both have the same level of structural relaxation.

Magnetically coupled MO double layer suitable for field modulation overwriting

Exchange coupled MO films like (PtCo/TbFeCo) and TbFeCo/TbFeCo) enable a very small external field of only 50 Oe for erase and write. Those are suitable media for a field modulation overwriting. In plane magnetized PtCo or low perpendicular anisotropy TbFeCo acts as the external field enhancing layer through exchange coupling with the TbFeCo recording layer.