Shuichiro Ogawa

Novel Preparation Method of Metal Particles Dispersed in Polymer Films and Their Third-Order Optical Nonlinearities

Polymer films containing nanometer-sized particles of Ag or Au were prepared by a simple process based on the reduction of organometallic compounds in a polymer matrix. Films were formed by casting a polymer solution admixed with an organometallic compound and a reducing agent onto a substrate. Third-order optical susceptibilities, χ(3), of these films were measured to be 2×10-9 esu for Ag and 1×10-8 esu for Au.

Electronic Structures and Optical Properties of GeTe and Ge 2Sb 2Te 5

The optical properties of GeTe and Ge2Sb2Te5 have been studied by means of the density functional theory (DFT) in the local density approximation (LDA). The electronic band structures were obtained by two methods, the plane wave (PW) and spherical wave (SW) expansions of the wave functions. GeTe was calculated to be semiconductive, and Ge2Sb2Te5 to be semimetallic. The frequency dependent optical constants such as refractive index and extinction coefficient were calculated and compared with those obtained experimentally. The origin of the peaks in the extinction coefficient spectra was assigned in terms of the transitions between Ge, Sb and Te p states. Dynamical calculations with respect to Ge2Sb2Te5 have also been performed in order to obtain an understanding of its structural features. The displacements of the Te atoms were found to be larger than those of the Ge and Sb atoms.

New concept of phase-change optical recording free from the initialization process

In general, phase change media have to be initialized prior to recording. Initialization for phase change optical disks involves crystallization of as-deposited amorphous recording films. An initialization-free technology will lead to a low production cost, which is very important for commercializing phase change optical disks. A five-layered phase change optical disk, which has a thin metal layer between the substrate and the lower dielectric layer, has a good overwriting jitter at high linear velocity. We propose to use the higher reflective amorphous state of a five-layered phase change optical disk as the prerecording state without initialization. Our proposed new concept of phase change optical recording has some advantages, such as initialization- free, large signal amplitude of a header field, servo stability and high performance of overwriting jitter. Our proposed disk shows the performance to the 2.6 GBytes digital video disk-random access memory (DVD-RAM) disk.

New layer structure of phase-change optical disk free from the initialization process

In general, phase change media have to be initialized prior to recording. Initialization for phase change optical disks involves crystallization of as-deposited amorphous recording films. An initialization-free technology will lead to a low production cost, which is very important for commercialization phase change optical disks. A crystallization assisted layer (CA layer) was deposited just before the sputtering of a recording layer GeSbTe. The CA layer is assist to crystallize GeSbTe film during sputtering. We have confirmed by X-ray diffraction method that the recording layer was crystallized just after sputtering. Our proposed disk with CA layer show the similar performance to the 2.6 GBytes digital video disk- random access memory (DVD-RAM) disk.

Polymer arrays for cellular adhesion

Microarray screening of polymer libraries for cellular adhesion was developed utilising a thin film of agarose to allow unsurpassed localisation of cell binding onto the array substrate and the discovery of cell specific polymers.