No abstract

To confirm the feasibility of realizing subterabyte or terabyte optical memories, we evaluated a multilayer read-only disk having 20 information layers. We propose a new disk structure, which is an alternative structure to reduce interlayer crosstalk, optimized by computer simulations. We fabricated multilayer read-only optical disks using a conventional manufacturing process for Blu-ray disk (BD) dual-layer media. Moreover, we improved the reproduction system to compensate for the large spherical aberration. From the experimental results, we obtained sufficiently low jitter values reproduced from a 20-layer disk. We confirmed the feasibility of the multilayer read-only disk with a capacity of 500 Gbytes.

Time-resolved laser fluorescence microscopy (TRLFM) is a useful tool to simultaneously investigate the intensity, location, type, and surrounding chemical environment of a fluorophore. In this study, we demonstrated the applicability of TRLFM for the adsorption of Eu(III) on a natural heterogeneous surface. Different adsorption species of Eu(III) were observed on the Makabe granite surface and its constituents (biotite, plagioclase, potassium feldspar, and quartz). Eu(III) heterogeneously adsorbed on biotite, plagioclase, and quartz and homogeneously on potassium feldspar. The histograms of the fluorescence decay rates of adsorbed Eu(III) indicated efficient quenching of Eu(III) fluorescence probably due to Eu(III)-surface interaction or the formation polynuclear hydoxo Eu(III) species on the surfaces. It was also revealed that single species of Eu(III) was observed on biotite and two species on plagioclase and potassium feldspar. The adsorption of Eu(III) on the granite surface was highly heterogeneous. The TRLFM measurements of different regions of the granite surface turned into the finding of Eu(III) with different fluorescence decay rates. Comparing with the fluorescence decay histograms of the mineral constituents, Eu(III) clearly adsorbed on the feldspar family. It was also found that Eu(III) adsorbed as an outer-sphere complex and on an altered mineral of the granite.

No abstract

We have observed that newly developed near-stoichiometric LiNbO3 crystals have three different types of energy levels: ultraviolet (UV) absorption centers just above the valence band, metastable shallow electron traps slightly below the conduction band, and deep traps located about 1.9 eV below the conduction band. Irradiation with UV light induced a stable absorption band extending from λ ≈650 nm to the absorption edge, which is caused by the photoinduced charge transfer from UV-sensitive absorption centers to deep traps via the conduction band. The electron lifetimes at shallow and deep traps could be controlled by doping elements and concentrations. Based on these favorable energy states, nonvolatile two-color holographic recording has been carried out by use of 852 nm recording beams and UV gating light. Nonvolatile readout by a single 852 nm beam was demonstrated for several hours. It was found that two-color recording from the pre-exposed, colored state can also be an attractive way of achieving nonvolatile readout. In this article, we investigate the photochromic effect observed in near-stoichiometric LiNbO3 and its use in two-color holographic recording.