| Budget Amount *help |
¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1995: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 1994: ¥1,700,000 (Direct Cost: ¥1,700,000)
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| Research Abstract |
We confirmed that permanent dipole moments were induced and resulted in the formation of an optical nonlinear phase in fused silica glass, when an electric field as high as 3kV/mm was applied to silica glass at 260C.Second harmonic waves at a wavelength of 0.532um were observed in the silica glass when YAG laser pulses at 1.06um was used as the excitation light source. The incident angles were changed from-60 to 60 degrees. Based upon the angle dependence of the SHG intensity, nonlinear susceptibility was estimated to be 0.3pm/V,which is the same order as that of quartz crystal. We found, furthermore, that the nonlinear phase was a layr as thin as 60um aand that the layr was placed near the surface contacted to the positive electrode during point it. On the contrary, we could not found tha formation of optical nonliear phase in a synthetic silica glass plate. It is worthwhile noting, here, that synthetic silica glass includes in general less impurities and defects than fused silica glass. We found the formation of optical nonlinear phase in the synthetic silica glass plate, if it had been exposed to X-ray radiation for 15min. before being poled. The X-ray radiation is well-known to induce some kinds of defects in silica glass. The absorption coefficient of the X-ray at a wavelength of 0.154nm is as high as 75cm-1, and thus the radiation induced defects must be localized in the surface layr as thin as 60um. When the defect layr was set to be contacted to the positive electrode durling poling, a strong second harmonic wave was observed. When the defect layr was contaced to the negative electrode, a weak seconfd harmonic wave was observed. Based upon these findings, we can conclude that the defects play a critical role in the formation optical nonlinear phase. The nonlinear phase was erased by electron beam irradiation or by rasing the temperature to 260C.
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