【作者】 刘浩；

【导师】 赵修建； 刘启明；

【作者基本信息】 武汉理工大学 ， 建筑材料与工程， 2007， 博士

【摘要】 玻璃的非线性光学效应不是非线性光学材料中最强的，但是玻璃具有独特的结构和性能，以及高的稳定性等一系列优点，成为光子开关等一系列非线性光学器件的候选材料之一。与其他体系相比，含有重金属离子或纳晶的玻璃，通常具有较高的非线性光学系数。因此，在含有重金属离子的氧化物玻璃中掺杂纳米晶体，在非线性光学领域的研究和应用方面就具有了重要的意义。本文首先对极化后不能产生非线性的Na₂O-Cs₂O-B₂O₃-SiO₂体系，掺杂CdS微晶后，进行了结构和非线性光学性能等方面的研究。以此为基础，对CdS微晶掺杂的PbO-B₂O₃-SiO₂体系进行了相关性能的研究，并计算了两种体系的二阶非线性极化系数。碱硼硅酸盐体系中，CdS添加量为3～5at％、ZnO／CdS为5～7（mol）之间时，CdS微晶可以正常析出；铅硅酸盐体系中，CdS添加量为3at％、ZnO／CdS为6～8（mol）时，CdS微晶可以正常析出。热处理析出的CdS微晶的晶型和晶粒发育状态受基础玻璃影响很大。碱系中，以六方型CdS为主要晶相的纳米晶体，伴有少量立方型CdS析出。提高热处理温度和时间，微晶的尺寸逐渐增大，透过光谱截止边和荧光光谱中特征峰红移，说明玻璃中存在明显的量子尺寸效应。铅系中，由于Pb对CdS中Cd的取代，使PbO／（PbO+SiO₂）为0.30时析出正交型CdS。碱硼硅酸盐体系基础玻璃极化后未观察到明显的SHG，说明极化后基础玻璃不会对二阶非线性产生影响；掺杂CdS微晶后，在未经极化的玻璃中可观察到明显的SHG，主要起源于颗粒表面Cd和S原子受激光作用发生极化，产生表面偶极层所致；极化后，SH强度显著增大，主要由偶极子的取向排列和六方型CdS的析出增强所致。玻璃SH强度的显著增大主要集中在极化初期的十几分钟内，提高极化温度和电压，有利于SH强度的增大。极化后的样品在阳极面表层存在厚约10μm的非线性层，主要由电极化诱导引起析出增强的六方型CdS做为产生光学非线性的主体。经过计算，具有最大SH强度的样品，其二阶非线性极化系数x^（2）为1.75pm／V，相干长度l_c（63.477°）为4.07μm。玻璃中非线性层的二阶非线性极化系数x^（2）估算为2.09pm/V，相干长度l_c（63.477°）为4.23μm。在CdS微晶掺杂铅硅酸盐玻璃中，热处理析出微晶后的玻璃样品未经极化处理，也都观察到了SHG；提高极化温度和电压，SH强度呈现逐渐增大的趋势；SH强度的显著增大主要发生在极化初期几分钟内，并且远大于相同条件极化后基础玻璃的SH强度，因此，SH强度的显著增大归因于玻璃中正交型CdS的极化诱导形变；极化后，阳极面表层存在一个厚约11μm的非线性层，由电极化诱导发生结构形变的正交型CdS作为产生SH信号的主体；具有最大SH强度的样品，二阶非线性极化系数x^（2）为3.49pm／V，远大于CdS微晶掺杂碱硼硅酸盐玻璃。更多还原

【Abstract】 With the development of optical communications and the coming of photon times,practical demands from all optical switch and space modulators have been presentedfor optical properties of materials, and the key for optical technology is thedevelopment of nonlinear optical materials. Although the nonlinear effects of glassare not the best in all kinds of nonlinear optical materials, it has special structure,properties, good chemic and thermal stability, and so on. Thus glass may be. one ofthe materials for nonlinear optical apparatus. Glasses contain heavy metal ions ornanocrystals generally have larger nonlinear optical coefficient than other systems.Therefore, doped with nanocrystals, the research and application of glasses containingheavy metal ions possess large significance.Contained with heavy metal ions, glasses have large nonlinear optical effects. Theanalysis of nonlinear optical mechanism will be more complicated with the doping ofnanocrystals. Na₂O-Cs₂O-B₂O₃-SiO₂ system, which can not generate second ordernonlinearity after poling treatment, was chosen to dope CdS nanocrystal andinvestigate the structure and nonlinear optical properties. Based on that, correlativeproperties of CdS doped lead silicate glasses were researched, and the nonlinearoptical coefficients of the two systems were both presented. Glasses were prepared bymelt-quenching method. Utilizing Maker fringe method, second-harmonic generation（SHG） has been investigated on the glasses systems throughheat-auxiliary-electric-field polarizing technique.In the alkali borosilicate glass system, CdS crystals could precipitate with thedopant at 3～5at% for CdS and the ratio of 5～7 for ZnO/CdS; And they were 3at%,6～8 for the lead silicate glass system.The states and types of CdS crystals precipitated were affected greatly by the kindsof base glasses. In alkali borosilicate system, hexagonal CdS was the main crystalphase, co-precipitated with a little cubic CdS. Nanocrystals grew gradually withenhancing the heat-treatment conditions, and the shift to long wave direction forcharacteristic peaks of optical transmission spectra and fluorescent spectra means theexistence of distinct quantum size effects. In lead silicate system, the displace of Pbfor Cd in CdS resulted in the precipitation of orthogonal CdS for samples with theration of PbO/（PbO+SiO₂） at 0.30. The state of CdS crystals for this system is not asgood as the alkali system, emitting strong fluorescence of surface and disfigurementin the nanocrystals.As for the CdS doped alkali borosilicate glasses, distinct SHG can not be observedin the base glass; Without any poling procedure, evident SHG can be observed in CdSdoped glasses, resulted from the polarization of Cd and S atoms on the surface of crystals by the application of laser light; After poling treatment, the SH intensityenhanced greatly, mainly from the directional array of dipoles and the increasingprecipitation of hexagonal CdS. Increasing the poling temperatures and voltages werein favor of the enhancement of SH intensity. In the 10μm nonlinear layer, thehexagonal CdS whose precipitation had been enhanced during the poling process isthe centre to generate the nonlinear optical effects. The second order nonlinear opticalcoefficient X^（2） for the sample with the largest SH intensity was calculated at 1.75pm/V,the coherent length was 4.07μm. Accordingly, they were 2.09pm/V and 4.231μm forthe nonlinear optical layer.As for CdS doped lead silicate glass system, SHG can all be observed for sampleswithout any poling treatment; The SH intensity increased with increasing the polingtemperature and voltage; The great enhancement of SH intensity happened at theinitial tens of minutes of the poling procedure, and it can be attributed to the inducedstructural distortion, which is the reason of the large enhancement for SH intensity;The x^（2） for this system was calculated at 3.49pm/V for sample with the largest SHintensity, which is larger than the alkali borosilicate glass system. The results meanthat in order to prepare glass materials with large x^（2）, it is logical to select leadsilicate glass system as the base glass to dope CdS nanocrystals.更多还原