两种Ni(Ⅱ)配合物的合成及三阶非线性光学性能

合成了两种新的Ni(Ⅱ)配合物,用UV、IR、MS和元素分析进行了表征。采用飞秒激光,运用简并四波混频法,研究了Ni(Ⅱ)配合物在非共振状态下的三阶非线性光学性能。它们的三阶非线性光学极化率χ(3)为3.21×10-13 esu和3.58×10-13 esu,非线性折射率n2为5.89×10-12 esu和6.58×10-12 esu,分子二阶超极化率γ为3.21×10-31 esu和3.57×10-31 esu,响应时间τ为54 fs和59 fs。探索了配合物的分子结构对三阶非线性光学性能的影响。结果表明具有大的高度离域的π电子共轭体系是获得较大三阶非线性光学性能的关键。     

5,12-二硫杂-7,14-二氮杂-5,7,12,14-四氢并五苯及其相关化合物二阶非线性光学性质的理论研究

在ZINDO方法基础上,按完全态求和(SOS)公式编制了计算分子二阶非线性光学系数β_ijk、β_u的程序.研究了不同取代基在5,12-二硫杂-7,14-二氮杂-5,7,12,14-四氢并五苯侧环取代衍生物及相关化合物的结构、光谱和二阶非线性光学性质。结果表明:侧环上取代推、拉电于基团对增大二阶光学非线性都有利;分子共平面,共轭作用强,对增大二阶光学非线性有利.     

Linear and nonlinear optical susceptibilities for a novel borate oxide BaBiBO4: Theory and experiment

The linear and nonlinear optical susceptibilities for different tensor components of BaBiBO₄ single crystals have been calculated using the full-potential linear augmented plane wave method. The results of these calculations are verified by our measurements of linear and nonlinear optical properties using Nd-YAG laser at fundamental wavelength 1064 nm. The calculated energy gap is in a good agreement with experimental energy gap data obtained by optical absorption. We present results for the imaginary and real parts of the frequency-dependent dielectric constant. The calculated birefringence of BaBiBO₄ is positive in agreement with the experimental data. Calculations are reported for the frequency-dependent complex part of second-order nonlinear optical susceptibilities . The linear and nonlinear optical susceptibilities are scissors corrected to match the value of the energy gap from the local density approximation calculations with the experimental value. The second harmonic generation efficiency of this compound is about five times larger than KDP (KH₂PO₄). It is crucial that we have obtained a large anisotropy of the second-order susceptibilities for three main second-order tensor components both experimentally and theoretically. The possible origin of the obtained anisotropy is discussed within a framework of the energy band calculations.     

Prediction of second-order optical nonlinearity of trisorganotin-substituted beta-Keggin polyoxotungstate

The dipole polarizabilities, second-order polarizabilities, and origin of second-order nonlinear optical (NLO) properties of trisorganotin-substituted beta-Keggin polyoxotungstate [XW9O37(SnR)3](11-n)- (X = P, Si, Ge, R = Ph; X = Si, R = PhNO2, PhCCPh) have been investigated by using time-dependent density functional response theory. This class of organic-inorganic hybrid complexes possesses a remarkably large molecular second-order NLO response, especially for [SiW9O37(SnPhCCPh)3]7- (system 5) with the static second-order polarizability (beta(vec)) computed to be 1569.66 x 10(-30) esu. Thus, these complexes have the possibility to be excellent second-order nonlinear optical materials. Analysis of the major contributions to the beta(vec) value suggests that the charge transfer from the heteropolyanion to the organic segment along the z-axis plays the key role in the NLO response of [XW9O37(SnR)3](11-n)-. The computed beta(vec) values increase as a heavy central heteroatom changes in the order Ge > Si > P. Furthermore, nitro substitution on the aryl segment and the lengthening of organostannic pi-conjugation are more important in enhancing the optical nonlinearity, especially for the latter factor. The present investigation provides important insight into the origin of the NLO properties of trisorganotin-substituted heteropolyoxotungstate.     

非线性光学环氧聚合物的近程结构对二次谐波产生弛豫特性的影响

设计合成了三种具有不同主链化学结构的二阶非线性光学功能化环氧聚合物,并对其化学结构进行了表征,考察了聚合物近程结构对材料极化后二次谐波产生弛豫特性的影响。极化后线型聚合物链节的扭转弹性回复是二次谐波产生弛豫的主要原因,在温度处于Ｔｇ 以下或Ｔｇ 附近时玻璃化转变温度的高低决定了二次谐波产生弛豫的快慢;聚合物交联后有助于提高二次谐波产生的稳定性,但此时聚合物单个链节结构的柔顺性成为影响二次谐波产生弛豫的主要原因,刚性越大,材料将具有更稳定的二次谐波产生性能。极化聚合物的二次谐波产生弛豫过程非常复杂,需要综合考虑聚合物材料的近程和远程结构因素。     

Increased interfacial thickness of the NaF, NaCl and NaBr salt aqueous solutions probed with non-resonant surface second harmonic generation (SHG)

Specific ion effects on the nonlinear optical response from the water molecules at the air/sodium halide solution interfaces are measured using non-resonant surface second harmonic generation (SHG). Procedures have been developed to monitor and remove the impurities in the salt solution samples to ensure measurement of small changes in the SHG signal. Quantitative polarization analysis of the measured SHG data indicated that the average orientation of the interfacial water molecules changed only slightly around 40 degrees with the increase of the bulk concentration of the three sodium halides, namely NaF, NaCl and NaBr, from that of the neat air/water interface. The observed significant SHG signal increase with the bulk salt concentration is attributed to the overall increase of the thickness of the interfacial water molecular layer, following the order of NaBr > NaCl approximately NaF. The absence of the electric-field-induced SHG (EFISHG) effect indicated that the electric double layer at the salt aqueous solution interface is much weaker than that predicted from the molecular dynamics (MD) simulations. These results provided quantitative data to the specific anion effects on the interfacial water molecules of the electrolyte aqueous solution, not only for the larger and more polarizable Br(-) anion, but also for the smaller and less polarizable F(-) and Cl(-) anions.     

(CH3)2N(C6H4)nCN系列分子二阶非线性光学系数的理论研究

在AM1和INDO/CI方法的基础上, 用自编程序计算了(CH3)2N(C6H4)nCN(n=1→6)系列分子的二阶非线性光学系数β~i~j~k和β~μ并系统地研究了共轭链长对分子二阶非线性光学系统的影响及β~μ对激光场频率的依赖关系(色散效应)     

N-取代吩噻嗪衍生物分子的结构和二阶非线性光学性质的理论研究

在ZINDO方法基础上, 按完全态求和(SOS)公式, 编制了计算分子二阶非线性光学系数βijk的程序。研究了各种取代基在吩噻嗪的氮上取代后衍生物的结构和二阶非线性光学系数。结论是N上取代推电子基对增大二阶光学非线性有利, N上取代吸电子基对增大二阶光学非线性不利。扩大共轭范围对增大二阶光学非线性有利。对上述结果在微观上给予了解释。     

基于硒化镓纳米片填充的空芯光纤超高二次谐波增强

与传统的光学晶体相比,全光纤功能器件由于和光纤系统的天然兼容性,被认为是下一代集成光学的重要研究方向,吸引了人们的广泛关注。然而,由于二氧化硅固有的中心反演对称性质,光纤中的二阶非线性光学过程仍有待探索,这在可调谐超快激光、全光信号处理、成像和光通信等商业全光纤非线性光学应用中具有重要意义。因此,我们提出了一种新的溶液填充方法,可有效地将具有高非线性的硒化镓纳米片直接沉积在长度达半米的空芯光纤(HCF)的内孔壁上。此外,采用制备的硒化镓纳米片-空芯光纤(GaSe-HCF)作为光频率转换器,其二次谐波(SHG)比嵌入MoS₂的HCF和普通HCF分别提高了2个数量级和3个数量级。我们的研究成果将拓展其它非线性材料在全光纤高端非线性光学和光电子学中的应用,并提供新的制备思路。     

盐酸氨基脲的二阶非线性光学性质研究

非线性光学(NLO)材料在光学信息处理、远程通讯等光电子学领域有着重要的应用,有效地预测和设计出二阶非线性光学材料所必需的非中心对称晶体,提高材料的综合性能是这一领域的研究热点。标题化合物盐酸氨基脲是以尿素为分子母体的有机离子型化合物,具有将有机和无机材料的优异性能集于一身的结构优势,是综合性能优的材料之一。     

酞菁铜/金属薄膜界面电位与光二次谐波特性分析

Using the Kelvin probe and the optical second harmonic generation (SHG) measurement, the Space charged phenomenon and the non-linear optical effects at the interfaces of the coppertetra-tert-butyl phthalocyanine (CuttbPc) Langmuir-Blodgett (LB) film deposited on a metal (AlorAu) coated glass slide substrate were in vestigated. The surface potentials decreaseas the film thickness increases and eventually approaches a saturated value. The SHG has been detected although there is a centro-symmetric systemin the Cuttb Pcmolecular, and avery strong SH signal can be investigated at 1260 nm band for Cuttb Pc/Al samples. According to a proposed physical model for Cuttb PcLB film/metal, the nonlinear mechanism were analyzed by using electromagnetic wave theory. It is considered that the enhanced SH peak of CuttbPc/Al is attributed to the strong surface potential aroused by SCIEF at the interface, and shows that the production of SH signal is correlated closely with the electrostatic phenomena at the interface.     

一种近红外光记录与存储材料——克酮酸染料的三阶非线性光学性质

克酮酸染料是一类新型的近红外吸收染料,由于具有良好的光热稳定性和荧光性能,因而在光记录与存储等领域有着潜在的应用价值.本文利用简并四波混频技术,在近红外区不同吸收波长,在脉宽为130 fs条件下研究了一种吲哚克酮酸染料在溶液和薄膜中的三阶非线性光学性质.该克酮酸染料在773 nm,四氢呋喃溶液中的共振三阶超分子极化率γ为5.3×10^-29esu,在薄膜中的共振三阶非线性极化率χ⁽³⁾值达到10^-8esu数量级.同时,对于三阶非线性光学响应及其动力学机制也进行了研究和探讨.     

Ellipsometric approach for the real-time detection of label-free protein adsorption by second harmonic generation

Second harmonic generation (SHG) was performed using a novel ellipsometric detection approach to selectively probe the real-time surface binding kinetics of an unlabeled protein. The coherence of nonlinear optical processes introduces new possibilities for exploiting polarization that are unavailable with incoherent methods, such as absorbance and fluorescence. Adsorption of bovine serum albumin (BSA) at silica/aqueous solution interfaces resulted in changes in the polarization state of the frequency-doubled light through weak, dynamic interactions with a coadsorbed nonlinear optical probe molecule (rhodamine 6G). Using a remarkably simple instrumental approach, signals arising exclusively from surface interactions with BSA were spatially isolated and selectively detected with high signal-to-noise. The relative intensities acquired during the kinetics experiments using both circularly and linearly polarized incident beams were in excellent agreement with the responses predicted from SHG ellipsometry polarization measurements. Analysis of the polarization-dependent SHG generated during BSA adsorption at glass/aqueous solution interfaces provided direct evidence for slow conformational changes within the protein layer after adsorption, consistent with protein denaturation. This polarization selection approach is sufficiently general to be easily extended to virtually all coherent nonlinear optical processes and a variety of different surface interactions and architectures.     

Ultrafast excited-state electron transfer at an organic liquid/aqueous interface

Ultrafast excited-state electron transfer has been monitored at the liquid/liquid interface for the first time. Second harmonic generation (SHG) pump/probe measurements monitored the electron transfer (ET) occurring between photoexcited coumarin 314 (C314) acceptor and dimethylaniline (DMA) donor molecules. In the treatment of this problem, translational diffusion of solute molecules can be neglected since the donor DMA is one of the liquid phases of the interface. The dynamics of excited-state C314 at early times are characterized by two components with exponential time constants of 362 +/- 60 fs and 14 +/- 2 ps. The 362 fs decay is attributed to the solvation of the excited-state C314, and the 14 ps to the ET from donor to acceptor. We are able to provide conclusive evidence that the 14 ps component is the ET step by monitoring the formation of the radical DMA cation. The formation time is 16 ps in agreement with the 14 ps decay of C314*. The recombination dynamics of DMA+ plus C314- was determined to be 163 ps from the observation of the DMA+ SHG signal.     

取代吡啶系列分子的光谱和二阶非线性光学性质的理论研究

采用AM1方法优化分子构型,用ZINDO方法研究了氨基、硝基取代的吡啶系列分子的电子光谱,并在此基础上用自编程序计算了这些分子的二阶非线性光学系数,对取代吡啶系列分子的二阶非线性光学系数的影响因素进行了探讨,并在微观上给予了解释。     

BaGa2MQ6 (M = Si, Ge; Q = S, Se): a new series of promising IR nonlinear optical materials

The four compounds BaGa(2)MQ(6) (M = Si, Ge; Q = S, Se) have been identified as a new series of IR nonlinear optical (NLO) materials and are promising for practical applications. They are isostructural and crystallize in the noncentrosymmetric polar space group R3 of the trigonal system. Their three-dimensional framework is composed of corner-sharing (Ga/M)Q(4) (M = Si, Ge; Q = S, Se) tetrahedra with Ba(2+) cations in the cavities. The polar alignment of one (Ga/M)-Q2 bond for each (Ga/M)Q(4) tetrahedra along the c direction is conducive to generating a large NLO response, which was confirmed by powder second-harmonic generation (SHG) using a 2090 nm laser as fundamental wavelength. The SHG signal intensities of the two sulfides were close to that of AgGaS(2) and those for the two selenides were similar as that of AgGaSe(2). The large band gaps of 3.75(2) eV, 3.23(2) eV, 2.88(2) eV, and 2.22 (2) eV for BaGa(2)SiS(6), BaGa(2)GeS(6), BaGa(2)SiSe(6), and BaGa(2)GeSe(6), respectively, will be very helpful to increase the laser damage threshold. Moreover, all the four BaGa(2)MQ(6) (M = Si, Ge; Q = S, Se) compounds exhibit congruent-melting behavior, which indicates that bulk crystals needed for practical applications can be obtained by the Bridgman-Stockbarger method. The calculated birefringence indicates that these materials may be phase-matchable in the IR region and the calculated SHG coefficients agree with the experimental observations. According to our preliminary study, the BaGa(2)MQ(6) compounds represent a new series of promising IR nonlinear optical (NLO) materials which do not belong to the traditional chalcopyrite-type materials such as AgGaQ2 (Q = S, Se) and ZnGeP(2).     

Reconsideration of second-harmonic generation from isotropic liquid interface: broken Kleinman symmetry of neat air/water interface from dipolar contribution

It has been generally accepted that there are significant quadrupolar and bulk contributions to the second-harmonic generation (SHG) reflected from the neat air/water interface, as well as common liquid interfaces. Because there has been no general methodology to determine the quadrupolar and bulk contributions to the SHG signal from a liquid interface, this conclusion was reached based on the following two experimental phenomena: the breaking of the macroscopic Kleinman symmetry and the significant temperature dependence of the SHG signal from the neat air/water interface. However, because the sum frequency generation vibrational spectroscopy (SFG-VS) measurement of the neat air/water interface observed no apparent temperature dependence, the temperature dependence in the SHG measurement has been reexamined and proven to be an experimental artifact. Here we present a complete microscopic analysis of the susceptibility tensors of the air/water interface, and show that dipolar contribution alone can be used to address the issue of the breaking of the macroscopic Kleinman symmetry at the neat air/water interface. Using this analysis, the orientation of the water molecules at the interface can be obtained, and it is consistent with the measurement from SFG-VS. Therefore, the key rationales to conclude significantly quadrupolar and bulk contributions to the SHG signal of the neat air/water interface can no longer be considered as valid as before. This new understanding of the air/water interface can shed light on our understanding of the nonlinear optical responses from other molecular interfaces as well.     

Mechanism of linear and nonlinear optical properties of the urea crystal family

First-principles calculations of the second-order optical response functions and the dielectric functions of urea [CO(NH(2))(2)] and some of its derivatives such as monomethylurea (H(2)NCONHCH(3), MMU), and N,N'-dimethylurea (H(3)CHNCONHCH(3), DMU) crystals are performed. On the basis of the density functional theory (DFT) in the local-density approximation (LDA), the highly accurate full-potential projected augmented wave (FP-PAW) method was used to obtain the electronic structure. Over a wide frequency range (0.0-10.0 eV), the dielectric constants and second-harmonic generation (SHG) susceptibilities of the urea crystal family have been obtained, and the results are in good agreement with the experimental values. The origin of the linear and nonlinear optical (NLO) properties of the urea crystal family has been analyzed by coupling the calculated electronic structure and optical spectrum. The prominent spectra of χ((2)) are successfully correlated with the dielectric function ε(ω) in terms of single-photon and double-photon resonances. The virtual electron (VE) and virtual hole (VH) processes have also been performed for the urea crystal family. From the research into the electron deformation density, crystal configuration, substitutional group, and so forth, it is found that the origin of the SHG of the urea crystal family is the charge transfer due to the strong "(?)push-pull" effect along the hydrogen bond, which favors a head-to-tail arrangement of the molecules and enhances the SHG response. The electron-donating substitutional group supplies more electrons to the electron-accepting group, and helps to form large dipoles in molecules. The influence on the NLO properties of the local symmetry of the substitutional group is also discussed in detail.     

新型非线性光学材料的分子设计: 系列螺旋共轭化合物的结构、光谱及二 阶非 线性光学性质的理论研究

采用AM1和ZINDO系列方法研究了螺旋共轭分子2,2'-螺二茚-1,1',3,3'-四酮及其腈基衍生物的几何构型,研究了各分子的稳定构型,并以稳定为基础,计算了这些分子的电子光谱,二阶非线性光学系数βμ,β0,及电荷转移,考察了取代基变化对βμ的影响,计算结果表明所设计分子兼具较大的二阶非线性光学系数和较高的透过率,有希望成为一类新型的二阶非线性光学材料。     

Synthesis and characterization of second-order nonlinear optical polyurethane with high thermal stability

A second-order nonlinear optical polyurethane was formed with an X-type multi-dimensional charge-transfer (CT) chromophore (DNPIPDHPI) and 3,3^′-dimethoxy-4,4^′-diphenyl diisocyanate. Simultaneous poling and polymerization and in situ second harmonic generation (SHG) measurement technique was carried on to evaluate the thermal stability of the poling induced orientation. The SHG signal of the poled polymer film was not decay below 150 °C and remains 90% of relative d₃₃ value at 200 °C, which is better than the results reported in literature. Comparison of thermal stability indicates that the X-type chromophores possess better property in controlling the decay of the SHG activity than classic chromophores.