束缚电荷对玻璃材料二阶光学非线性的影响

对电场极化后薄膜材料与体材料二阶光学非线性的比较研究表明,二者具有相同的极化和弛豫特性．分析了束缚电荷的形成及其对二阶光学非线性的影响,定性地从理论上指出,由束缚电荷产生的电场对薄膜及体材料的极化和弛豫过程起了决定作用． 关键词： 二阶非线性 玻璃 极化 束缚电荷     

热及电场诱导的多载流子模型及分析

提出了热及电场诱导的多载流子模型。在完全耗迟近似下,得出了耗尽区厚度和电场强度的计算公式。公式表明,耗尽区厚度、耗尽区最大电场与诱导时外界电压成平方根关系,而二次谐波的转换效率与应用电压成平方关系。耗尽区的厚度为3-8um;耗尽区的最大场强为1－4V/nm,并位于阳极表面下1－6um.     

偶氮化合物的电晕极化薄膜及其非线性光学性能研究

在有机物中,给体受体取代的偶氮化合物,由于它们具有几乎最高的二阶非线性光学效应以及作为一类新的、有前景的电光材料而倍受重视。在这方面,材料分子的非中心对称的有序排列是首先重要的。把非线性光学活性分子如偶氮化合物溶于聚合物中,再用电场极化方法得到分子有序排列的聚合物薄膜,这是目前认为最有效的材料宏观形态工程。     

电晕极化电光聚合物调制器的制备研究

随着光通信的飞速发展,高速聚合物电光调制器的应用更加重要广泛.聚合物薄膜是制造聚合物电光调制器的基础.文中介绍与分析了聚合物电光调制器聚合物薄膜的电晕极化制备方法.     

介电超晶格结构极化设备的研究

针对介电超晶格结构的特殊极化问题,自行研制了极化设备.研究了Windows操作系统下实现高频精确定时的高性能定时器法.基于此方法实现了极化设备的任意波形发生器及信号采集功能.研制开发了高精度0～10 kV稳压电源,产生满足要求的极化电压.利用这种设备完成了化学计量比钽酸锂晶体的极化实验.结果表明设备运行稳定可靠,性能良好.     

硼酸铅玻璃的光学二次谐波产生

对硼酸铅玻璃体材料样品进行热辅助的平板电场极化(简称热极化)后,通过观察其光学二次谐波(SHG)信号的强弱,得到了不同组分的样品的最佳极化温度,发现其最佳极化温度与玻璃化温度满足一定的关系;同时得到了不同组分的样品在各自的最佳极化温度条件下极化后的二次谐波信号强度与组分的关系;经过对一种组分的样品进行细致研究,发现样品的二次谐波信号强度随着极化电压的增大而增大,并满足幂函数关系.利用有效偶极子释放模型解释了样品的二次谐波信号强度与极化电压之间的超平方关系 关键词： SHG 玻璃 极化     

Synthesis and characterization of main‐chain NLO oligomers and polymer that contain 4‐dialkylamino‐ 4′‐(alkylsulfonyl)azobenzene chromophores

An ω‐amino carboxylic acid monomer that contained a nonlinear optical (NLO) chromophore was prepared by a convergent synthesis. Strategies for selective protection/deprotection of the amino and carboxylic acid functionalities were developed. The protected monomer, 4‐[N‐(4‐benzyloxycarbonyl)butyl‐N‐methylamino]‐4′‐[2″,5″‐bis(decyloxy)‐4″‐(phthalimidomethyl)benzylsulfonyl]azobenzene, could be deprotected selectively or sequentially to give HOOC‐monomer‐N‐phthaloyl, benzyl‐OOC‐monomer‐NH₂, or HOOC‐monomer‐NH₂. Sequential synthesis was performed to yield main‐chain NLO dimers and tetramers. This was accomplished by selective deprotection and dicyclohexylcarbodiimide coupling. The HOOC‐monomer‐NH₂ was polymerized by treatment with diphenylphosphoryl azide to give a main‐chain NLO polyamide. The monomer, dimer, tetramer, and polymer NLO materials were characterized by ¹H, ¹³C, IR, and UV–visible spectroscopy as well as by gel permeation chromatography, differential scanning calorimetry, and elemental analysis. The NLO properties of these materials were measured. Thin films of the oligomers and polymer were prepared by spin casting on indium‐tin oxide coated glass. The second‐order NLO properties of the oligomers and polymer thin films were studied by in situ corona poling/second‐harmonic generation and attenuated total reflection methods. The optimal poling temperatures were significantly lower than the melting temperatures or glass‐transition temperatures of the oligomers and polymer. The poling efficiency increased in the following order: monomer, oligomers, and polymer. An electro‐optic coefficient of 4 pm/V at 1.06 μm was obtained for the polymer. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 546–559, 2000     

Influence of the polymer structure on the achievement of polar orientation in high glass transition temperature nonlinear optical polyimides by photo-assisted poling

We have used combinations of light, heat, and electrostatic fields to investigate the orientation of nonlinear azo-chromophores chemically incorporated into high glass transition temperature (T_g) polyimides. A number of nonlinear optical polyimides have been synthesized in which the interaction between the nonlinear optical chromophore and the polymer main chain was systematically altered to determine to what extent this steric interaction influences the orientation of the nonlinear chromophore. Chromophores in polymers may be oriented by a number of methods: (a) polarized light at room temperature (i.e., photo-induced orientation or PIO), (b) polarized light and electric fields (i.e., photo-assisted poling or PAP) at temperatures ranging from room temperature to the polymer T_g, and (c) electric fields at T_g (thermal poling). While thermal poling and PIO are usually possible, PAP depends strongly on the molecular structure of the polymer. Previously we have shown that PIO can be accomplished at room temperature in a system where the nonlinear chromophore is embedded into the polyimide main chain via the donor substituent, and this orientation can only be thermally erased at temperatures approaching T_g. In this article we show that, whereas photoisomerization can efficiently depole donor-embedded polyimides in a matter of few minutes at room temperature, PAP does not induce any polar order. This behavior is in marked contrast to a structurally related, side-chain, nonlinear polyimide, in which the azo chromophore is tethered via a flexible linkage to the polymer backbone. In this case some PAP occurs even at room temperature, while no PAP is observed for a donor-embedded system with a similar T_g. We suggest that the orientation during PAP below T_g in the side-chain polyimide is primarily due to the movement of the azo side chains, and there is a very little coupling of this motion to the main chain. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1669–1677, 1998     

Electric field-induced dipole reorientation in oriented nylon 11 by in situ infrared spectroscopy

Dipole reorientation under the influence of an electric field is investigated in oriented nylon 11 films with polarized infrared spectroscopy for the amide A and amide I bands. Butterfly-shaped hysteresis loops are obtained from peak intensity versus applied electric field strength. Least-squares Gaussian curve fitting of the resolved multiple contributions to the amide I peak show that the components change in either a continuously reducing S-shaped fashion, or in butterfly-shaped curves under ac poling fields. Time-dependent studies of the absorption intensities show that both ordered and disordered species switch towards the electric field direction with the application of electric fields higher than the coercive field. Upon field removal, only the disordered species show orientation relaxation away from the field direction. Below the coercive field, neither species responds orientationally to the field. © 1996 John Wiley & Sons, Inc.