The study on mutiphoton absorption induced photorefractive effect and fixing process

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Multiphoton induced photorefractive effect and thermal fixing process of the refractive index distribution in a photorefractive crystal had been inverstigated. The summaries in this research results are followings.1. Thermal fixing process was investigated with a LiNbO_3 crystal. It was succeeded in continuous reading the hologram more than six hours without any degradation of the recorded data.2. The bit data recorded with a focused beam in the crystal were also fixed.3. Two-photon absorption process in a non-doped LiNbO_3 crystal was inveratigated. A titanium sapphire laser was used for a light source. The induced refractive index distribution was observed wiht a phase-contrast microscope. It was very verified that photorefractive effect was induced with two-photon absorption process.4. As an application of two-photon process in a photorefractive crystal, multilayred optical memory was demonstrated. Seven layrs recording and reading with little crosstalk was presented. The distance between neighboring bits was 4 mum and neighboring layrs was 20 mum.