噻二唑衍生物分子的电子光谱与三阶非线性光学性质

含噻二唑环偶氮类芳香有机化合物具有良好的有机非线性光学性能.采用密度泛函理论B3LYP方法和6-311++G(d,p)基组对6个噻二唑衍生物分子进行结构优化与频率计算,运用含时密度泛函理论对其吸收光谱进行理论计算,采用有限场方法及自编程序计算其三阶非线性光学性质(NLO).结果表明,6个分子的吸收波长在361~383nm范围内,属于近紫外区.组成噻二唑衍生物分子的羟基苯环与噻二唑环均不共面,-CH3或Cl引入到羟基苯环的邻、间、对位后,其共面程度与三阶NLO系数γ均按邻、间、对位取代递减.同一位置,引入-CH3比引入Cl原子的三阶NLO系数γ大.因此,在羟基苯环的邻位引入较强的供电子基,可以设计成为良好的三阶非线性光学材料.     

Y型均三嗪类衍生物三阶非线性光学性质研究

采用密度泛函理论B3LYP/6-31+G*方法对含Y型均三嗪类衍生物的6个分子(Y1-Y6)进行几何构型优化,对其最优构型采用TD-DFT (TDB3 LYP/6-31+G*)计算电子吸收光谱,用有限场FF方法及自编程序计算三阶非线性光学(NLO)性质.结果表明,6个含Y型均三嗪类有机分子的三阶非线性光学系数γ值为1010数量级个原子单位(10-30 esu),显示出良好的三阶非线性光学性能.在其三支链的末端引入不同的推、拉电子基团(Y2→Y6),对其电子光谱和三阶非线性光学响应具有明显的影响.引入强供电子基团,γ增大幅度较大,有利于改善体系的三阶非线性光学性质,从而可获得良好的非线性光学材料.     

Y型均三嗪类衍生物三阶非线性光学性质研究

采用密度泛函理论B3LYP/6-31+G*方法对含Y型均三嗪类衍生物的6个分子(Y1-Y6)进行几何构型优化,对其最优构型采用TD-DFT(TDB3LYP/6-31+G*)计算电子吸收光谱,用有限场FF方法及自编程序计算三阶非线性光学（NLO）性质。结果表明,6个含Y型均三嗪类有机分子的三阶非线性光学系数g值为1010数量级个原子单位(10-30 esu),显示出良好的三阶非线性光学性能。在其三支链的末端引入不同的推、拉电子基团（Y2→Y6）,对其电子光谱和三阶非线性光学响应具有明显的影响。引入强供电子基团,g增大幅度较大,有利于改善体系的三阶非线性光学性质,从而可获得良好的非线性光学材料。     

Investigation of third-order nonlinear optical susceptibility in polymer complexes of diarylidenealkanones

The third-order nonlinear optical susceptibility in polymer complexes of diarylidenealkanones has been investigated by the third harmonic generation technique at a wavelength of 1.06 μm. The macroscopic nonlinear susceptibility χ ⁽³⁾ measured is compared with the calculated γ values of the second-rank molar hyperpolarizability tensor. It is demonstrated that low-molecular chromophores can be used in syntheses of the stable polymer composite systems with a high nonlinear optical susceptibility. A further improvement in the nonlinear optical properties of complexes between deprotonated chromophores and high-basicity polymers can be achieved using the proposed methods. __________ Translated from Fizika Tverdogo Tela, Vol. 42, No. 11, 2000, pp. 2099–2102. Original Russian Text Copyright ? 2000 by Ten’kovtsev, Yakimanski, Lukoshkin, Dudkina, Boehme.     

一种侧链共轭聚噻吩衍生物薄膜的三阶非线性光学响应

合成了一种侧链共轭的聚噻吩衍生物聚3-（5′辛基-噻吩乙烯基）噻吩（POTVTh）,并通过溶液旋涂制备了聚合物薄膜.吸收光谱显示该聚合物薄膜具有较小的禁带宽度和宽的光谱响应.采用Z扫描技术在800 nm下用飞秒激光器研究了该聚合物薄膜的三阶非线性光学特性,非线性吸收系数为5.63×10^-7cm/W,非线性折射率为-6.38×10^-11 cm²/W,三阶非线性极化率为4.21×10^-9esu,比侧链未共轭的 关键词： 聚噻吩衍生物 侧链共轭 三阶非线性极化率 非线性折射率     

Investigation of third-order nonlinear optical properties of conjugated benzodioxal derivatives

An investigation of third-order nonlinear optical characterization of newly synthesized conjugated benzodioxal derivatives has been done by using nanosecond Z-scan technique at 532 nm. The molecules demonstrate self-defocusing effect with intensity dependent refractive index (n₂) of the order of 10⁻¹⁴ cm²/W. The measured molecular TPA cross-section is ranging from 2.47 ×10⁻⁴⁷ cm⁴ s/photon to 6.00 cm⁴ s/photon. Their input-output curves indicate that there is a clear optical power limiting behavior with the limiting threshold in the range 125-181 μJ. The main factor to exhibit the observed nonlinearity in these molecules is the presence of charge donor and acceptor groups. The increased conjugation length increases the nonlinear refraction and increased electron density enhances the nonlinear absorption. The molecules exhibit good nonlinear optical properties, comparable to those of regular azoaromatic compounds. Therefore, the molecules investigated here are promising candidates for optical power limiting devices.     

Z-scan determination of third-order nonlinear optical nonlinearity of three azobenzenes doped polymer films

The third-order nonlinear response of methyl red (MR), methyl orange (MO) and p-dimethylamino benzene arsenic acid (PDBAA) doped polyvinyl alcohol (PVA) films are studied by using the Z-scan technique under 532 nm and 1064 nm excitations. The larger third-order nonlinear refractive index of PDBAA doped PVA film is discussed in terms of fall of the energy level in excited state for the effect of heavy-atom arsenic. At the end, the second hyperpolarizabilities of the films are estimated and the figures of merit are evaluated for their value of applications in ultra-fast all-optical devices.     

Investigation of third-order nonlinear optical properties of two azo-nickel chelate compounds

This paper investigates the third-order nonlinear optical properties of two azo-nickel chelate compounds by the optical Kerr gate method at 830 nm wavelength with pulse duration of 120 fs. Both of the two compounds exhibited large third-order optical nonlinearity. The second-order hyperpolarizability,γ, of Compound 1 is of 1.0 × 10^-31 esu. Due to the charge transfer, the γ of Compound 2 with electron donor and acceptor group is 4.9 × 10^-31 esu, which is a four-time enhancement in comparison with Compound i. The absorption spectra show that the electron push-pull effect, which induces intramolecular charge transfer, leads to the increased optical nonlinearity.     

Studies of third-order nonlinear optical properties of C60 by the optical Kerr effect

60 at 1.064 μm is determined by the optical Kerr effect in toluene solution. Values of -6.5×10^-33 esu and 2.0×10^-32 esu for the real and imaginary parts of γ, respectively, are obtained. Based on the experimental results and symmetry constraint, it is concluded that a three-level model is not adequate to describe the third-order nonlinearity of C₆₀. It is also inferred that the non-resonant γ of C₆₀ should be positive in sign, which is in agreement with reported off-resonant measurements of γ of C₆₀ by third-harmonic generation. Received: 3 September 1997/Revised version: 1 December 1997     

Large third-order nonlinear optical properties of C70 fullerene in the infrared regime

The nonlinear third-order optical susceptibility of C₇₀ in a toluene solution is measured for the first time by the method of degenerate four-wave mixing using 10 ns laser pulses at 1.06 m. The third-order susceptibility X _in ⁽³⁾ is 5.6×10^–12 esu for a C₇₀ toluene solution at a concentration of 0.476 g/l. The correspondent magnitude of the hyperpolarizability ₁₁₁₁ of the C₇₀ molecule is 1.2×10^–30 esu which is in a good agreement with the prediction given by the model of a free electron in a spherical box.     

有机大分子三阶非线性光学材料的研究进展

根据分子结构特征评述了各类有机大分子三阶非线性光学材料结构与性能的关系。概述了三阶非线性光学性能的计算。分析了材料分子设计原理和展望了应用前景。     

Pressure and temperature effects on the third-order nonlinear optical properties in GaAs quantum dots

This work is used in the density matrix formalism and the effective mass approximation to study the third harmonic generation coefficient in a GaAs disc-shaped quantum dot with parabolic confinement potential. It is discussed the strong and weak confinement regime. The results show that the third harmonic generation coefficient is strongly dependent on the excitonic pair localization. The study is extended to consider effects such as hydrostatic pressure and temperature to show that it is possible to induce a blue-shift and/or red-shift on the resonant peaks of the third harmonic generation coefficient.     

聚苯胺/碳纳米管复合体的制备及其三阶非线性光学性能研究

通过原位吸附-受限生长聚合法成功制备了聚苯胺/碳纳米管(PANI/MWCNT)复合体.红外光谱和拉曼光谱证实了在碳纳米管(MWCNT)表面的包覆层为聚苯胺(PANI).紫外—可见吸收光谱表明随着MWCNT含量的增加PANI的吸收发生红移且强度提高.扫描电子显微镜和透射电子显微镜观察发现，PANI/MWCNT复合体直径为40—70nm，其中PANI的包覆层厚度约为15—20nm.利用四波混频方法测试它们的三阶非线性光学系数，结果发现PANI/MWCNT复合体的三阶非线性光学系数比纯PANI大，这说明在MWC 关键词： 碳纳米管 聚苯胺 复合体 三阶非线性光学系数     

Three-field noise correlation via third-order nonlinear optical processes

We report experimental observation of three-field noise correlation between two coexisting four-wave mixing (FWM) signals and the probe signal in a coherently-prepared rubidium vapor system. The two FWM signals in a double-Λ type quasi-four-level atomic system are obtained in different directions via their respective phase-matching conditions and can be detected individually. These signals and the probe beam are found to be strongly correlated or anticorrelated with each other.     

The nonlinear optical susceptibility and electro-optic tensor of ferroelectrics: first-principle study

The nonlinear optical properties of some ABO₃ materials (BaTiO₃, KNbO₃, LiTaO₃ and LiNbO₃) are studied by density functional theory (DFT) in the local density approximation (LDA) expressions based on first-principle calculations. Our goals are to give the details of the calculations for linear and nonlinear optical properties, including the linear electro-optic (EO) tensor for some ABO₃ structures with oxygen octahedral structures using first-principles methods. These results can then be used in the study of the physics of ferroelectrics, specifically, we present calculations of the second harmonic generation response coefficient X _ijk ⁽²⁾ (−2ω, ω, ω) over a large frequency range for ABO₃ crystals. The electronic linear EO susceptibility X _ijk ⁽²⁾ (−ω, ω,0) is also evaluated below the band gap. These results are based on a series of the LDA calculations using DFT. Results for X _ijk ⁽²⁾ (−ω, ω,0) are in agreement with experiments below the band gap. The results are compared with the theoretical calculations and the available experimental data.     

Investigation of third-order nonlinear optical properties of NNDC-doped PMMA thin films by Z-scan technique

A novel chalcone derivative, (2E)-1-(2,4-di- chloro-5-fluorophenyl)-3-[4-dimethylamino)phenyl]prop-2-en-1-one, abbreviated as NNDC, was prepared and characterized by elemental analyses, infrared (IR) and proton nuclear magnetic resonance (¹H NMR) spectrum, and thermal analyses. The NNDC-doped poly(methyl methacrylate) (PMMA) thin films with five different doping concentrations by weight were prepared by using a spin-coating method. Their linear optical properties were investigated by using a prism coupling measuring system. The third-order nonlinear optical properties of NNDC in 1,2-dichloroethane (NNDC/1,2-dichloroethane) solution and NNDC-doped PMMA (NNDC/PMMA) films were investigated by using the laser Z-scan technique with 20 ps pulses at 532 nm. A self-focusing effect was observed from the Z-scan curves for solution and thin films and the nonlinear refractive index of the film increases with the increase of the doping concentration. In addition, nonlinear absorption was negligible for all samples. The magnitude of third-order nonlinear refraction index n ₂ and the third-order nonlinear susceptibility χ ⁽³⁾ for thin films were 10⁻¹⁵ m²/W and 10⁻⁹ esu, respectively, which are about three orders larger than that of NNDC/1,2-dichloroethane solution. Some necessary analyses were presented. The results show that this material is a promising candidate for application in the nonlinear optical devices at 532 nm.     

Computational studies of third-order nonlinear optical properties of pyridine derivative 2-aminopyridinium p-toluenesulphonate crystal

In this note, method of Lie symmetries is applied to investigate symmetry properties of time-fractional K(m, n) equation with the Riemann–Liouville derivatives. Reduction of time-fractional K(m, n) equation is done by virtue of the Erdélyi–Kober fractional derivative which depends on a parameter α. Then soliton solutions are extracted by means of a transformation.     

Relationship between third-order nonlinear optical properties and magnetic interactions in open-shell systems: a new paradigm for nonlinear optics

Although most third-order nonlinear optical (NLO) materials are closed-shell singlet systems, this Letter theoretically shows that the third-order NLO properties are drastically enhanced in symmetric open-shell diradical systems with intermediate diradical character and further reveals that this enhancement is associated with the ferromagnetic and antiferromagnetic interactions. This new paradigm opens up a promising area for designing new third-order NLO materials.     

Measurement of third-order nonlinear optical susceptibility of synthetic diamonds

Diamonds are wide-gap semiconductors possessing excellent physical and chemical properties;thus,they are regarded as very appropriate materials for optoelectronic devices.Based on the Kerr effect,we introduce a simple and feasible method for measuring the third-order nonlinear optical susceptibility of synthetic diamonds.In the experiments,synthetic type I diamond samples and transverse electro-optic modulation systems are utilized.As for the laser with the wavelength of 650 nm,the third-order susceptibility and Kerr coefficient of the diamond samples are obtained at χ(3)1212= 2.17 × 10-23 m2/V2 and S44 = 1.93 × 10-23 m2/V2,respectively.