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Polymerization mechanism of epoxy material is based on ring-opening reaction, which generally results in lower shrinkage. In this study, the effect of different photosensitive dyes on the shrinkage characteristics of room temperature fast-curable epoxy polymer media for blue laser holographic recording is reported. Two photosensitive dyes, namely EB and EY dyes, for the holographic epoxy resin photopolymer material were investigated. The EB dye can induce free radical from TEA, which in turn can initiate acrylamide monomer polymerization in holographic material after irradiated by a 405 nm blue laser. The photosensitivity of dye can influence the shrinkage properties of the epoxy media after recording process. The measurement results indicate that the epoxy media addition with higher photosensitive EB dye has lower shrinkage value of about 0.25 %, which is much smaller than general accepted value of about 0.5 %. Index Terms--Blue laser holography, diffraction efficiency, epoxy, photosensitizer, shrinkage.

Holographic data storage is the most promising data storage technology in the next generation due to the advantages of the ultra-high data storage density and high data transfer rate. Dimensional stability of storage media and photorefraction effect of the grating are the two most important factors for holographic storage. In this study, a blue laser holographic material with low shrinkage is developed. The organic-inorganic hybrid matrix is triethoxysilylpropyl polyethyleneglycol carbamate (TSPEG) homogeneously bonded with tetraethyl orthosilicate (TEOS) prepared by sol-gel method. Diallyl phthalate pre-polymer (DAPP) and 9,10-Phenanthrenequinone (PQ) were used as a monomer and a photoinitiator, respectively. Optical data recording was performed by a blue laser source with a wavelength of 405 nm and the intensity of laser is 2 mW/[cm.sup.2]. The photoinduced free radical polymerization of DAPP in the presence of PQ can be initiated by the blue laser irradiation. The inorganic backbone limits the shrinkage resulting from the polymerization and increases the rigidity of the matrix. The shrinkage measurement shows that the blue laser holographic material with TSPEG/TEOS = 0.2 (molar ratio) has very low shrinkage of about 0.145% after recording the hologram. Index Terms--Blue laser holographic data storage media, low shrinkage, organic-inorganic hybrid matrix, photopolymerization.

The new optical disk format, called forward versatile disk (FVD), has been developed in Taiwan. Some physical technologies, such as recording on narrower groove, new modulation code, and new error correction code (ECC) have been verified. The feasibility for producing triple-layer FVD has been proven. In addition to the read-only memory (ROM) type, the format for the recordable/rewritable FVD type is also developed. These technologies of FVD with red laser will be applied to the next generation. Blue high-definition (HD) FVD will adopt most red HD FVD technologies. For higher recording capacity FVD, technologies such as super-RENS and multilevel recording for next-generation FVD are continuing to develop. Index Terms--Forward versatile disk (FVD), high definition (HD), multilayer, multilevel, super-RENS.

In this paper, the magnetic domain formation process on a moving disk for [Tb.sub.23][Fe.sub.77] magneto-optical recording thin film under the magnetic field modulation recording was investigated by a new simulation method. The simulation results showed that the convex prior edge of the domain was instantly formed and pinned when the magnetic field changed from low state to high state. Then, the domain boundary was lengthened opposite to the disk moving direction without changing the width during the high state of the applied magnetic field. As the magnetic field changed from high state to low state, the concave posterior edge of the domain was simultaneously formed and pinned, and the domain became a closed chevron shape. Both edges closely resemble the Curie temperature contour. There existed a threshold applied magnetic field strength, and the domain could not be formed when the applied field strength was below the threshold value. The value of the threshold field was approximately the same as the demagnetizing field around Tc, but reversed in polarity, and it increased with the laser power. The domain width increased as the applied field increased above the threshold value, and it rapidly became saturated when the applied field was about 30 Oe greater than the threshold value. There also existed a threshold laser power, below which the domain could not be formed. The threshold power was 3.3 mW for [Tb.sub.23][Fe.sub.77]. The domain width increased monotonically with the laser power for high applied magnetic field, and it increased (then decreased) with the laser power when the applied magnetic field was closed to the threshold value.

For studying the influence of the current passed through a metal line for the magnetic cells on semiconductors, we prepared two types of the devices. Case I is that only one patterned permalloy cell on top of the insulated metal strip, and two cells are beside the strip. Case 2 is that all three patterned magnetic cells are on top of the strip. The magnetic field needed to reverse the magnetization of a submicrometer-size permalloy single domain cell with aspect ratio of 6 is larger than that of a unpatterned millimeter-size permalloy thin film due to the dimension effect. Magnetic force microscopy images of the patterned cells before and after applying various electrical currents were investigated. We have observed that: 1) the magnetic field produced by the word line will not change the magnetic configuration of the magnetic cells near the wires; 2) the magnetic field produced by the word line is quite uniform; and 3) for small aspect ratio of the submicrometer magnetic cells ( Index Terms--Electron beam (E-beam) lithography, magnetic domain reversal, magnetic domain structure, magnetic force microscope.

We used alternate sputter method to deposit GdTbFeCo alloy films. The Kerr spectra of these films are relatively flat in the wavelength range from 450nm to 850nm. and increased slightly below 450nm. The Kerr angle increased with increased FeCo content in the GdTbFeCo film, and this relationship is independent of wavelength in the range from 450nm to 850nm.