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转换器的关键。重金属增加了光学玻璃材料的非线性。本研究计画从玻璃形成性质及光学特性量测的观点，探讨碲酸盐玻璃系统中，具有高二阶非线性的材料选择。用铁模浇铸法研究了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。然后将其抛光成厚度为0.5mm的光学平板样品。TeO_2-WO_3-La_2O_3和TeO_2-WO_3-PbO系统具有较宽的玻璃形成区和较清晰的透明性。特别是在TeO_2-WO_3-La_2O_3系统中，观察到了着色现象，且着色现象与玻璃组成有关。结果表明，在20mol%的TeO_2-WO_3-La_2O_3体系中，微黄的TeO_2-WO_3-La_2O_3体系的紫外吸收限为375 nm，褐黄的TeO_2-WO_3-La_2O_3体系的紫外吸收限为420 nm。La_2O_3的摩尔浓度对显色有明显的影响。玻璃熔制过程中WO_3（黄色）→WO_2（棕色）的反应似乎受到La_2O_3含量增加的抑制，其中La_2O_3中的CeO_2杂质起氧化剂的作用。通过测量不同玻璃材料的紫外-可见透过率和三次谐波产生（THG）特性，阐明了玻璃组成、吸收限和非线性光学性能之间的关系。对于这些碲酸盐玻璃，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）玻璃体系是一种很好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。我们在这些碲酸盐玻璃中成功地观察到了二次谐波现象，发现其二次谐波常数较高，为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.