共查询到17条相似文献,搜索用时 250 毫秒
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准相位匹配(QPM)理论上能够充分利用晶体的非线性光学系数、无走离效应,在光学频率转换中具有非常大的优势。铌酸锂晶体(LiNbO3, LN)具有高非线性光学系数、宽通光范围和低生长成本,因此基于铌酸锂铁电畴结构设计获得的周期极化铌酸锂晶体(PPLN)成为准相位匹配技术的理想选择。目前制备PPLN晶体最常用的方法是外加电场极化法,制备过程中,电极结构的参数对极化过程至关重要。本研究基于实时监测下的电场极化过程,结合有限元分析,对不同电极结构的空间电场分布进行分析,发现电极边缘出现电场极大值,而电极内部的电场分布相对均匀。基于这一现象,本文提出了一种多通道电极结构的设计方案,以实现极化空间内部电场的均匀分布。本研究采用十通道电极进行极化实验,通过表征每个通道的占空比,发现内部八个通道的占空比大小均匀且在50%±5%范围,通过晶体的倍频实验验证发现十通道周期极化样品中中间通道相对边缘通道的非线性转换效率明显提升并分布均匀,证明其中间通道具有占空比可控的均匀极化结构,为极化空间电场均匀化设计提供了一种高效合理的设计方案。 相似文献
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外加电场法制备周期极化铌酸锂工艺的众多结构参数对极化进程有潜在的影响.本文采用数值方法系统的分析了周期极化的重要结构参数的影响,这些参数包括绝缘层介电常数、绝缘层厚度、电极宽度、外加电压幅度和光栅周期.证明了对极化进程影响最为显著的是电极宽度、外加电压幅度和光栅周期,它们应该是设计极化结构时需要考虑的主要参数.相对的,绝缘层介电常数、绝缘层厚度对极化进程的影响在一定条件下可以忽略.本文由此推论了一种简洁合理的极化结构设计步骤.另外,本文得到了光栅周期与最优电极宽度的二次拟合公式,它为设计提供了依据,降低了复杂程度. 相似文献
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将TiO2引入压电纤维复合材料(MFC)的粘结层以提高其介电常数,调控MFC极化和驱动过程中电场分布,实现了对MFC性能的优化.采用有限元分析的方法探究了粘结层介电常数对MFC电场分布的影响,指导设计了实验方案.采用切割-填充法制备了在粘结层聚合物中引入TiO2的MFC.铁电性能测试结果表明,MFC剩余极化强度随粘结层中TiO2质量分数的增加呈现先增大后减小的趋势,在粘结层中TiO2质量分数为8wt;时达到最大值.MFC驱动性能随TiO2质量分数变化的趋势与剩余极化强度一致,电场驱动下自由应变在TiO2质量分数为8wt;时达到峰值,为2.31 με.研究表明,引入TiO2调节粘结层介电常数可有效改善MFC的性能. 相似文献
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为探究前驱粉体对Ag/AgCl电极电化学性能的影响,利用固相球磨法加入表面活性剂以及不同的干燥方法制备AgCl粉体,寻找出优化制备工艺,并制备了Ag/AgCl多孔电极.利用SEM、XRD对粉体进行微观结构分析表征,利用eDAQ电化学工作站和低噪声前置放大器噪声测试装置对电极进行电化学性能测试,讨论微观结构对电极的极化性能、短期稳定性以及电化学噪声水平的影响,并测试其外加电场响应性能.结果表明,固相球磨中加入CTAC(十六烷基三甲基氯化铵)球磨4 h并利用冷冻干燥法所制备的AgCl粉体分散性好,形貌均一,粒径1μm以下;所制备的复合Ag/AgCl电极结构呈多孔状,开孔率约32.78;;电极的交换电流密度大,约1.0035 A·cm-2,不易极化;两电极一致性好,极差电位小,约为0.005 mV;电极具有优良的短期稳定性,电极电势波动不超过0.01 mV/24 h,在1 Hz频率处功率谱密度可低至1.02 nV/Hz,为水下微弱电场探测提供了极为有利的测试基础. 相似文献
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采用磁控溅射的方法在以SrRuO3 (SRO)为底电极的(001)取向的SrTiO3基片上制备了外延BiFeO3 (BFO)薄膜,并以氧化铟锡(ITO)和金属Pt为上电极构架了ITO/BFO/SRO和Pt/BFO/SRO两种薄膜电容器,研究上电极对外延BFO薄膜铁电性和反转特性的影响.结果表明,两种薄膜电容器均体现了良好的饱和电滞回线,当测试电场为333 kV/cm时,ITO/BFO/SRO和Pt/BFO/SRO两种电容器的剩余极化强度分别为47.6 μC/cm2和56 μC/cm2,矫顽场分别为223 kV/cm和200 kV/cm.此外,两种薄膜电容器都具有良好的保持和抗疲劳特性.通过反转和非反转电流对时间的积分,可以计算出真实的极化强度.当反转电压幅值为17 V时,ITO/BFO/SRO和Pt/BFO/SRO两种电容器电流的反转时间分别为0.48 μs和0.32μs,真实极化强度的计算值约为41μC/cm2和47 μC/cm2,此计算值和铁电净极化强度的测量值符合的很好. 相似文献
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本文研究了低光强下锂组分对纯铌酸锂晶体的可见光折变、紫外光致吸收及紫外光折变性能的影响,发现了光折变中心种类和数量随晶体组分的渐变行为.在组分较低的同成分晶体中,大量本征缺陷形成Q极化子,因而在可见光波段表现出较弱的光生伏打效应;在组分较高的近化学计量比铌酸锂晶体中,双极化子是主要光折变中心,从而引起较高的光生伏打电场.而纯铌酸锂晶体的紫外光致吸收以及紫外光折变性能则具有相似的组分依赖关系.它们随组分的增加过程可分为两个不同的阶段:当组分小于49.70 mol;时,随组分增加缓慢升高,而当组分高于49.70 mol;时,随组分突然猛增并迅速升高.上述实验结果也可采用本征缺陷由Q极化子主导向双极化子主导的渐变过程进行解释. 相似文献
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Pb(Zr1-xTix)O3 (PZT)由于具有优异的综合性能而成为应用最广泛的压电陶瓷。之前研究工作证明了与直流极化(DCP)和交流极化(ACP)相比,采用交流极化和直流极化相结合的方法能进一步提高弛豫铁电单晶材料的压电性能。本工作报道了直流极化、交流极化和交流极化+直流极化后PZT-4压电陶瓷的介电性能和压电性能,探究了直流极化、交流极化和交流极化+直流极化的最佳极化条件。在最佳交流极化+直流极化条件下, PZT-4 压电陶瓷的压电常数(d33)为350 pC/N,相比直流极化(305 pC/N)、交流极化(320 pC/N)分别提高了15%和9%。交流极化后的PZT-4陶瓷样品的应变值(0.08%)高于进行直流极化样品的(应变值0.05%),表明交流极化可以有效提高PZT-4陶瓷的应变值,但是交流极化后应变曲线的滞后增大不利于器件应用,交流极化对硬性压电陶瓷的影响还需要进一步探讨。 相似文献
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AbstractIn recent years the electro-optic polymers emerged as an important branch of material science. This growth and interest is fundamentally motivated by practical application of these materials in second-order nonlinear optics and in waveguiding configuration. Indeed, these materials marry excellent optical quality of amorphous σ bonded polymers with enhanced first hyperpolarizability of imbedded organic nonlinear optical molecules. Although a big progress was achieved with them, concerning particularly the science, understanding and applications, some problems remain still incompletely solved, particularly the stability of induced polar order by the application of external electric field and the molecule aggregation. In this review paper we recall techniques of thin film fabrication, poling, characterization of NLO properties and discuss more precisely problems of molecule aggregation as well as the temporal decay of polar order. A novel 3D second-order NLO chromophores, namely the [2] paracyclophanes, which may help to limit the aggregation, are proposed. We show, in particular, that this molecule can be poled in doped PMMA thin films. Practical applications of electro-optic polymers are also reviewed and discussed. 相似文献
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Daniele Marinotto Claudia Dragonetti Alessia Colombo Danilo Pedron Silvia Pietralunga 《Journal of Non》2011,357(10):2075-2080
The “swelling-poling-deswelling” technique is a new procedure of poling crosslinked polymeric network carrying covalently attached NLO (nonlinear optical) chromophores. It is based upon a solvent-swollen crosslinked polymeric network before submission to poling. Under electrical poling, the matrix is deswelled without heating above the polymer Tg (glass transition temperature) obtaining a significant improvement of the stabilization of the alignment of the chromophores and therefore of the SHG (second harmonic generation). We determined the d33 values of DR1 chromophore linked in different manner to PMMA (polymethylmethacrylate) and polystyrene. Crosslinked PMMA gives very good results, in fact the 40% of the d33 value remains after 4 months respect to d33 evaluated a couple of hours after poling. Interestingly the same stability in the time of the d33 is observed with the crosslinked polystyrene matrix. In terms of d33 after poling, the two systems carrying DR1 (Disperse Red 1) moieties covalently attached to the polystyrene matrix (side-chain and crosslinked) behave in a similar manner, but in terms of stability, the linear polymeric system is the best (75%), higher than all systems investigated. 相似文献
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Shunsuke Murai Ryosuke Hattori Tomohiko Matoba Koji Fujita Katsuhisa Tanaka 《Journal of Non》2011,357(11-13):2259-2263
Wavelength-selective enhancement of optical birefringence has been observed in a tellurite glass containing silver nanoparticles (Ag NPs) induced via thermal poling. The birefringence appears as an optical rotation of linearly polarized light; a large optical rotation is observed at around the wavelength of localized surface plasmon resonance (LSPR) of Ag NPs. The optic axis is oriented along the electric field applied during the thermal poling, suggesting that birefringence induced in the glass matrix through the thermal poling is drastically enhanced by the NPs at around the LSPR. Because of the birefringence of the matrix, the wavelength of LSPR shifts depending on the polarization state of the incident light, which in turn induces the polarization dependence of the real part of the refractive index via the Kramers–Kronig relation. 相似文献
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K. V. Saban J. Thomas P. A. Varughese G. Varghese 《Crystal Research and Technology》2002,37(11):1188-1199
The influence of electric field on crystal nucleation in a saturated solution has been studied both theoretically and experimentally. The classical equations for nucleation have been used to determine the free energy of formation, critical radius of the cluster and the concentration of the critical nuclei. The theory shows that an externally applied electric field can modify the free energy of formation of a crystalline cluster in its aqueous solution. The impact of the field will be stronger on large molecules. Two experimental set ups have been designed to study the nucleation of crystals in saturated aqueous solutions, in the presence of electric fields. Experiments conducted using a metal coordination compound bis‐ thiourea zinc chloride show that electric fields of strength around 105 V/m would increase its nucleation. 相似文献