Study of nonlinear optical glass fcr total wavelength converters for photonic network

开发具有高二阶非线性光学常数的合适材料是获得高性能波长变换器的关键。重金属增加了光学玻璃材料的非线性。本课题从玻璃形成特性和测量光学特性的角度，研究了具有高二阶非线性潜力的碲酸盐玻璃体系中合适材料的选择。通过在铁模上浇铸熔体，研究了TeO_2-WO_3-X（X=La_2O_3,Nb _2O_5,Bi_2O_3,PbO, Ta_2O_5,TiO_2）体系的玻璃形成区域。然后我们将它们抛光成0.5mm厚度的光学平板样品。其中TeO_2-WO_3-La_2O_3和TeO_2-WO_3-PbO体系具有更宽的玻璃形成区域和更清晰的透明度。特别是在TeO_2-WO_3-La_2O_3体系中，观察到与玻璃组分有关的显色现象。淡黄色TeO_2-WO_3-La_2O_3（20mol%）和褐色TeO_2-WO_3-La_2O_3（10mol%）的紫外吸收边分别为375nm和420nm。色度明显取决于La_2O_3的摩尔浓度。La_2O_3含量的增加抑制了玻璃熔融过程中WO_3（黄色）→WO_2（棕色）的反应，La_2O_3中的杂质CeO_2起氧化剂的作用。通过测量各种玻璃材料的UV-VIS透明度和三次谐波（THG）特性，阐明了玻璃成分、吸收边与非线性光学性能之间的关系。这些碲酸盐玻璃的THG常数为0.28-1.6（x10^<-12>esu）。结果表明，TeO_2-WO_3- X（X=PbO, La_2O_3）玻璃体系是一种高性能波长转换器材料。我们也尝试了对TeO_2-WO_3PbO玻璃的极化。我们成功地观察了这些碲酸盐玻璃的SHG现象，发现其SHG常数较高，为54pm/V。

Development of a suitable material with high second-order non-linear optical constant is important to obtain high performance wavelength converter. Heavy metals increase non-linearity of optical glass materials. This research project has studied selection of a suitable material in tellurite glass systems, which has a potential of high second-order non-linearity, from the view pint of glass forming properties and measuring optical characteristics. We investigated glass formation region on TeO_2-WO_3-X(X=La_2O_3,Nb _2O_5,Bi_2O_3,PbO, Ta_2O_5,TiO_2) systems, by casting melts on a mold of iron. Then we polished them into an optical flat plate sample with 0.5mm thickness. It was the TeO_2-WO_3-La_2O_3 and TeO_2-WO_3-PbO systems, which has wider glass forming region and clearer transparency. Especially, in the TeO_2-WO_3-La_2O_3 system, coloration phenomenon was observed and was depending on the glass composition. UV absorption edge is 375nm for light yellowed TeO_2-WO_3-La_2O_3(20mol%) and 420nm for browned TeO_2-WO_3-La_2O_3(10mol%), respectively. Coloration is depending on the molar concentration of La_2O_3 clearly. It seems that the reaction, WO_3(yellow)→WO_2(brown) in glass melting, is suppressed by the increasing of La_2O_3 content where impurity of CeO_2 in La_2O_3 acts as oxidizing reagent. The relationship among glass composition, absorption edge and nonlinear optical properties was clarified by measuring UV-VIS transparency and third-harmonic generation(THG) characteristics for various glass materials. THG constant is 0.28-1.6(x10^<-12>esu) for these tellurite glasses. It is concluded that TeO_2-WO_3- X(X=PbO, La_2O_3) glass system is useful as a material for high performance wavelength converter. We have also tried poling of TeO_2-WO_3PbO glasses. We have succeeded to observe SHG phenomenon ot these tellurite glasses and found that its SHG constant is relatively high as 54pm/V.