PbO-GeO_2ガラス中のGeの配位状態のEXAFS研究 : 構造と光学非線形性の関係

概要

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The coordination state of Ge ions in PbO-GeO_2 glasses was examined using EXAFS. It was found that a part of Ge ions changed from 4-fold to 6-fold coordination state on addition of PbO, which had been expected from the property-composition relations. The fraction of 6-fold coordinated Ge ions, N_6, increased with increasing PbO content up to 20 mol%, then decreased on further increase in PbO content. However, the maximum N_6 was about 13% and twice as small as that in binary alkali germanate glasses. The refractive index of the glasses, n, increased with increasing PbO content, showing a very faint hump around 20 mol% PbO, and third-order nonlinear optical susceptibility, X^<(3)>, monotonously increased from 1.0×10^<-13> esu at PbO=0 to 5.6×10^<-13> esu at PbO=40 mol% with an increase in PbO content. The absence of germanate anomaly in n-or X^<(3)>- composition relation was explained by the smaller effect of change in coordination state of Ge ions in comparison with that by PbO addition.
1993-09-01