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

开发合适的具有高二阶非线性光学常数的材料对于获得高性能的波长转换器具有重要意义。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光学特性测量的角度出发，研究了在具有高二阶非线性潜力的碲酸盐玻璃系统中选择合适的材料。在铁模上浇注熔体，研究了TeO_2-WO_3-X(X=La_2O_3，Nb_2O_5，Bi_2O_3，PbO，Ta_2O_5，TiO_2)系统玻璃的形成区域。然后将它们抛光成厚度为0.5 mm的光学平板样品。TeO_2-WO_3-La_2O_3和TeO_2-WO_3-PbO系玻璃形成区较宽，透明度较高。特别是在TeO_2-WO_3-La_2O_3系统中，观察到了变色现象，且变色现象与玻璃组成有关。淡黄色TeO2-WO_3-La_2O_3(20mol%)和棕色TeO_2-WO_3-La_2O_3(10mol%)的紫外光吸收边分别为375 nm和420 nm。显色明显依赖于La_2O_3的摩尔浓度。当La_2O_3中的CeO_2杂质作为氧化剂时，玻璃熔制过程中的WO_3(黄色)→WO_2(棕色)反应似乎被La_2O_3含量的增加所抑制。通过测量不同玻璃材料的UV-Vis透过率和三次谐波(THG)特性，阐明了玻璃成分、吸收边和非线性光学性质之间的关系。这些碲酸盐玻璃的THG常数为0.28-1.6(x10^-12；ESU)。结果表明，TeO2-WO3-X(X=PbO，La_2O_3)玻璃系统是一种很有前途的高性能波长转换材料。我们还尝试了TeO_2-WO_3PbO玻璃的极化。我们成功地观测到了这些碲酸盐玻璃的倍频现象，发现其倍频常数较高，达54 pm/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.