主客体掺杂极化聚合物薄膜二阶非线性光学特性研究

【作者】 孙彦星；

【导师】 王文军；

【作者基本信息】 聊城大学 ， 光学， 2011， 硕士

【摘要】 有机非线性光学材料特别是偶氮类非线性光学材料,由于其二阶非线性光学特性优良,成为光电子学、光通信等领域研究的热点。本文利用旋涂法制备了偶氮掺杂聚合物薄膜,通过测量紫外-可见吸收谱、厚度及折射率表征其物理特征,用电晕极化的方法对聚合物薄膜极化,测量了其宏观非线性光学特性。主要内容如下:1.选取了取代基不同三种偶氮材料作为客体,采用溶胶-凝胶技术制备了主客体掺杂的旋涂膜,并采用电晕极化使薄膜极化,研究客体材料取代基对偶氮掺杂薄膜的二次谐波产生(SHG)的影响,研究结果表明,含有不同取代基的偶氮材料,取代基给(受)电子能力越强,二次谐波产生强度的极化饱和值越大。用马克条纹法测量各体系的有效倍频系数,发现其倍频系数的大小关系是NDMA/PMMA薄膜最大,其值为4.420 pm/V,IDMA/PMMA薄膜次之,其值为0.794 pm/V,DEA/PMMA薄膜最小,其中为0.748 pm/V。分析认为由于偶氮苯不同取代基给(受)电子能力不同,导致微观一阶超极化率β不同,从而使得偶氮分子被极化的难易程度不同,最终决定了有效倍频系数不同。2.研究了IDMA/PMMA薄膜在主客体材料掺杂比不同及温度不同的情况下对于二次谐波产生的变化的影响。实验发现随着客体浓度的增大,SHG表现出先是增大然后变小的变化规律,分析认为在掺杂浓度较低时,二次谐波产生的增大是由于偶氮分子含量的增加所致,当浓度较高时,分子间相互作用不可忽略,致使偶氮材料的结构发生扭转,一阶超极化率β变小,使得SHG降低;随着温度的升高SHG先增大后减小,存在一个最佳值,其值为90℃,分析认为,这个温度接近薄膜的玻璃转变温度,薄膜处于粘滞态,其中的偶氮分子很容易在高电场下取向。3.研究了极化温度和薄膜厚度对IDMA/PMM薄膜的SHG弛豫特性,并对其弛豫曲线用Origin软件进行了拟合。实验发现,平均驰豫时间随温度的增大而变短;随着薄膜厚度的增加,平均弛豫时间增加。4.研究了薄膜厚度和极化温度对薄膜中偶氮分子偏转角度的影响。实验发现,随温度的增大,分子偏转的程度增大;而随着厚度的增大,分子偏转程度是不断的减小的。更多还原

【Abstract】 Because of its excellent second-order nonlinear properties, Optical nonlinear organic materials especially azo class nonlinear optical materials have been extensity studied In optoelectronics, optical communication researches. In this paper, The PMMA doped azo compound films were prepared by using spin coating method. Their thickness, index of refractive and UV-Vis spectra were measured. The films were poled by corona poling method. The main works were as follows:1. The PMMA doped three different azo compound films were prepared by using spin coating method. Second harmonic generation (SHG) density were detected by real-time corona poling method. For azobenzene molecule with different substituent, the stronger the ability of push (pull) electron is, the bigger the value of SHG is. For the three systems the effective frequency-doubling coefficient is different. The result was disused: because of the ability of push (pull) electron is different; the first-order hyperpolarizability is different which determine the molecule will be poled easily or not.2. Nonlinear optical properties of IDMA/PMMA films were studied in different density, experimental result shows that the SHG raise at first then decline as the density of Azo-Dye molecules rise. Analyzed we know that at lower density the SHG raise because Azo-Dye molecules manifold, when the density is larger enough, intermolecular repulsion and intermolecular attraction which made the second order Polariabilityβsmaller can’t be ignored, and SHG decline.3. Decay property of poled IDMA/PMMA film was detected at different temperatures, and Decay curve were fitted by Origin software. Results show that the average relaxation time becomes shorter with temperature increase; Decay property of poled IDMA/PMMA film was also detected at different thickness, Results show that the average relaxation time becomes longer with thickness increase.4. The effection of Molecular deflection angle at different thickness films and different temperature were studied. Result shows that the average alignment factor becomes bigger with temperature increase and For the films with different thickness, with the thickness increase the average alignment factor decrease.更多还原