|Budget Amount *help
¥2,900,000 (Direct Cost : ¥2,900,000)
Fiscal Year 2000 : ¥800,000 (Direct Cost : ¥800,000)
Fiscal Year 1999 : ¥2,100,000 (Direct Cost : ¥2,100,000)
Second-order optical nonlinearity dose not theoretically occure in optical isotropic materials. Thus. second-order optical nonlinearity was considered not to be observedinorganic glasses because of their optical isotropy. However, after suitable treatment, it can be observed in inorganic glasses. One of the treatments is the thermal poling of the glasses. We found second-harmonic generation from various kinds of silica and silicate glasses. There is several models to interprete the nonlinearity. Two of them are dipole orientation model and space charege model. To enhance the space charge effect, the kinds of additives comes to so impotant. Alkali ions are small and easily drift in the glasses, but the relaxation is so fast. Therefore, we add alkaline-earth oxides into the glasses in order to cause large space charge. As a result, each glass containing alkaline-earth oxide show second harmonic generation after thermal poling. From EPMA(Electron Probe Micro Analysis)data, the migration of alkali-earth ions have been observed. The degree of the migration depends on the size of alkaliearth ions and the degree of the migration increases as ion radius increases. In specific, the migration of Ba^<2+> is the largest, on the other hand that of Mg^<2+> is the smallest. The space charge effect depends on the gradient of electric fleld, and thus the most remarkable gradient can be expected in MgO, and consequently the largest secon-harmonic generation is observed in MgO containg glasses.
For glass-ceramics, we successtully prepared CdS microcrystals-doped glasses and find the secondharmonic generation. During the thermal poling treatment, the joule energy caused by the electric resistance of the glasses causes the formation of CdS high-temparature crystal phase. Thus, the intensity of secondharmonic generation of poled glasses is much larger than that of heat-treatment glass-ceramics without poling.