【作者】 于庆霞；

【导师】 陶绪堂； 张少军；

【作者基本信息】 山东大学 ， 材料物理与化学， 2010， 硕士

【摘要】 非线性光学材料在频率转换、光参量振荡、电光调制和通讯等现代技术中,扮演着越来越重要的角色。从1961年发现二次谐波现象以来,人们在新的非线性光学材料探索方面做了大量工作。目前,产生可见、紫外光的非线性光学晶体,如KTiOPO4 (KTP),LiB3O5 (LBO),和CsLiB6O10 (CLBO),已经能基本满足实际应用。在红外波段,虽然出现了ZnGeP2,AgGaS2等晶体,但是他们的一些难以克服的缺点(如高光学质量的单晶生长困难；热导率低,热膨胀各向异性大；在可见波段透过率低等)限制了其广泛的应用。BaTeMo2O9是一种新型的红外非线性光学材料,其粉末倍频效应为600×a-SiO2。我们课题组首次成功生长出高光学质量的大块单晶,并研究了其基本性质。我们自行搭建了测量单晶二阶非线性光学系数的马克(Maker)条纹法光学测试平台。这些都为BaTeMo2O9晶体非线性光学性质的研究奠定了基础。本论文对BaTeMo2O9单晶的非线性光学特性进行了系统研究,主要内容包括：1、概述了非线性光学的起源、发展历程,并对已有的非线性光学晶体进行了简单介绍。总结了测试晶体二阶非线性光学系数的几种方法,位相匹配法操作和计算都比较简单,常用于一些系数的测量；而马克条纹法可以测量几乎全部的非线性系数,是目前最常用的测试方法。2、简单介绍了BaTeMo2O9晶体的基本物理性质。采用我们自己探索出的助溶剂体系,成功生长了尺寸达到30×23×18 mm3的BaTeMo2O9晶体；晶体的透过波段为0.4-5μm；晶体为负光性双轴晶并具有较大的双折射。确定了BaTeMo2O9晶体的折射率主轴(X,Y,Z)与结晶学轴(a,b,c)的相对关系：Z//b,(a,Y,)=25.5°,(c,X)=24.603°。3、搭建了马克条纹实验测量平台。实验装置包括激光器、门积分仪、位移控制器、光电倍增管、计算机等。实验数据采集过程由计算机通过软件PortMaster进行自动控制,采集的数据精确度高；采集的数据用软件MakerDP处理,在MakerDP中,既可以根据输入的理论公式绘制曲线,也可以导入实验数据,绘制实验曲线,并且可以将理论曲线和实验曲线绘在同一个图中进行比较。在MakerDP中对实验数据进行拟合及分析后,可以计算出晶体的非线性光学系数。简单介绍了马克条纹测量中不确定度来源及分析如何准确采集Maker条纹数据。4、研究了BaTeMo2O9晶体的非线性光学性质。根据晶体的主轴折射率色散方程理论计算了BaTeMo2O9晶体的位相匹配曲线；给出了晶体的二阶非线性光学系数矩阵；采用马克条纹法与位相匹配法测量了全部非零系数的大小及相对符号,最大的系数为d31=9.88 pm／V；给出了有效非线性系数的表达式,并结合得到的系数矩阵理论计算了BaTeMo2O9晶体的有效非线性系数,并得到有效非线性系数最大值为10.3 pm/V。更多还原

【Abstract】 Nonlinear optical (NLO) materials are widely used in optical devices such as frequency conversion, optical parametric oscillation (OPO), optical modulation and telecommunications. A lot of researches have been done since the first observation of second-harmonic generation (SHG) in 1961. Up to now, materials for visible and UV light can meet the need of practical application primarily, such as LiB3O5 (LBO), CsLiB6O10 (CLBO) and KTiOPO4 (KTP). In the infrared (IR) region, a number of materials such as ZnGeP2 and AgGaS2 have been reported, but some drawbacks still exist that limit their applications. For instance, these crystals are hard to grow with good optical quality. They also have low thermal conductivity, large anisotropy of thermal expansion, and low transparency in the visible region. Therefore, great efforts have been devoted to the development of new NLO crystals for the IR region.BaTeMo2O9 (BTM) is a new infrared NLO compound, its Kurtz powder second-harmonic generation (SHG) efficiency is about 600×α-SiO2. High-quality bulk single crystal of BTM, with dimensions up to 30×23×18 mm3, has been grown by flux method in our group. Its basic properties have been studied and an experimental setup for Maker fringe platform to determine the second-Order optical nonlinear coefficients was constructed. This makes the ground to study second-order nonlinear optical properties of monoclinic BaTeMo2O9 bulk single crystal.We studied the second-order nonlinear optical properties of BTM systematically, and the main works are as follows:1、Overview of the origin and the development of the nonlinear optics. A brief introduction of the nonlinear optical crystals has been carried out. Several methods to test the second-order nonlinear optical coefficients are summed up. The phase matching method is easy to operate and calculate and is commonly used in the measurement of the nonlinear coefficients. The Maker fringe technique can be used to measure almost all of the nonlinear coefficients, and is currently the most commonly used method.2、A brief introduction of the basic physical properties of crystal BaTeMo2O9 is presented. High-quality bulk single crystal of BTM, with dimensions up to 30x23x18 mm3, has been grown by flux method in our group. It has a good transparency from 0.4 to 5μm at room temperature. It is a negative biaxial crystal with a large birefringence. The crystal physic axes (X, Y, Z, with the setting nx<ny<nz) of BTM do not correspond to the crystallographic reference axes (a, b, c), and the orientation were determined as b//Z:(a, Y)=25.5°, (c,X)=24.603°.3、An experimental setup of Maker fringe platform to determine the Second-order optical nonlinear coefficients was constructed. It includes mainly laser, integrator, move controller, photomultiplier tube, and computer. The experimental data acquisition process is automatic controlled by the computer software PortMaster, which has high accuracy. The data is then processed by MakerDP. MakerDP can draw curves with the given theoretical formula or the imported experimental data, and it can make comparison of theoretical curve and experimental curve drawn on the same graph. The optical nonlinear coefficients are calculated by fitting and analyzing the experimental data in MakerDP. A brief introduction of the source of the uncertainty in the Maker fringe technique, and how to collect data accurately is reported.4、The optical nonlinear properties of BaTeMoaO9 crystals were studied. The phase matching curves were calculated according to the Sellmeier equation, and the second-order nonlinear optical coefficients matrix of the crystal was presented and all of the nonzero coefficients, the relative signs were obtained by using the Maker fringe technique and phase matching method. The largest coefficient d31=9.88 pm/V; the calculated maximum effective nonlinear coefficients is 10.3 pm/V.更多还原