New Hologram System Using Photochemical Holeburning Phenomena

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1.IntroductionThese days, the interests in optical memory based on persistent spectral hole burning (PSHB) are increased because of its possibility of the applicaton to high density optical memory. PSHB has been observed for an organic dye doped in polymer and rare earth or transition metal doped in inorganic cyrstal or glass. Room temperature PSHB phenomena have been already observed for Sm^<2+> doped fluoride crystal and glasses. However, these materials'GAMMA_<ih> (inhomogeneous line width)/GAMMA_h (homogeneous line width) which is the parameter of data multiplicity is an order of unity. For the application of PSHB materials to optical memory, high operating temperature and a large GAMMA_<ih>/GAMMA_h should be required. Therefore, in this study, the relationship between the optical hole and glass structure is examined.2.Results and Discussionphoto-chemical hole burning (PHB) can be applied for data storaging system as well as a powerful method for studying the local structure around optical centers. We have studied both aluminum, magnesium and silicon ion effects and alkali ino effects on the hole burning and phonon sideband for borate glasses which show up the PHB at room temperature. The hole burning was measured on ^5D_0-^7F_0 transition of Sm^<2+> and phonon sideband apectrum for ^5D_0-^7F_0 transition of Eu^<3+>. The hole width is closely related to the local structure change, especially, seems to deacrease with decreasing non-bridging oxygens produced around raee rarth ion. In the case of sodium alumino-borate glasses, the hole width decreases cosiderably with increasing alumina. The the ratio of GAMMA_<ih>/GAMMA_h of 85B_2O_310Al_2O_35aN_2OlSm_2O_3 glass is about 80 at room temperature, which is the largest value reported up to now. Moreover, the hole-burning speed has been drastically improved by means of the X-ray irradiation to the specimens.