含苯乙烯桥侧链三枝分子的二阶非线性光学性质

采用密度泛函理论B3LYP/6-311+g(d,p)方法对含苯乙烯桥侧链均三嗪类衍生物的8个分子(Y1-Y8)进行几何构型优化,对其最优构型采用TD-DFT(TDB3LYP/6-311+g(d,p)),计算电子吸收光谱,用有限场FF方法及自编程序计算二阶非线性光学（NLO）性质。结果表明,8个分子的μ（或0）值为104数量级个原子单位(10-29 esu),显示出良好的二阶非线性光学性能。在其三支链的末端引入强供电子基团（如-N(CH3)2或-N(CH2CH3)2）比引入弱供电子基团及吸电子基团,更有利于改善体系的二阶非线性光学性质,从而可获得良好的非线性光学材料。     

Determination of the macroscopic optical properties for the NAEC/PEK-c guest–host polymer films

The polyetherketone (PEK-c) guest–host polymer films doped with (4′-nitro)-3-azo-9-ethyl-carbazole (NAEC) were prepared. The films were poled by corona-onset poling at elevated temperature (COPET). The orientational order parameter of the chromophores NAEC in poled polymer film was determined by measuring the absorption spectra of the films before and after being poled. By using the two-level model, the measured dispersion of the refractive index of the polymer film, and the dispersion of the first hyperpolarizability of chromophore NAEC, the dispersion of the macroscopic second-order nonlinear optical (NLO) and linear electro-optic (EO) coefficients was evaluated for the NAEC/PEK-c guest–host polymer film.     

聚合物薄膜中生色团分子间的相互作用对其宏观二阶非线性的影响

制备了3-(1,1-二氰基噻吩)-1-苯-4,5-二羟基-H-噻唑(DCNP)与聚醚醚酮(PEK-c)组成的主客掺杂聚合物薄膜,用Maker条纹法测量了不同掺杂浓度下薄膜的二阶非线性系数χ₃₃⁽²⁾.实验结果表明,聚合物中生色团的含量高到一定程度,其宏观二阶非线性随生色团含量的增加反而下降.本文在考虑聚合物中生色团分子相互作用的情况下,修正了聚合物宏观二阶非线性与生色团的含量之间的关系,此时聚合物宏观二阶非线性与生色团的含量已非简单的正比关系.讨论了生色团分子间 关键词：     

Synthesis and nonlinear optical properties of branched pyrroline chromophores

New tricyanopyrroline (TCP) chromophores with rigid–flexible dendron were prepared for second‐order nonlinear optical (NLO) application. The chromophores were fully characterized using ultraviolet‐visible spectroscopy, nuclear magnetic resonance spectroscopy and mass spectrometry. Thermal gravimetric analysis (TGA) revealed that the chromophores had excellent thermal stability. Large λ_max and high solvate chromic effects revealed that the chromophores had large second‐order optical nonlinearity. The electro‐optic coefficients (r₃₃) were measured in the chromophores‐doped poly(bisphenol A carbonate) films at the fundamental wavelength of 1310 nm, and the highest γ₃₃ achieved was 217 pmV^?1. Copyright © 2010 John Wiley & Sons, Ltd.     

Computational study of chiral molecules with high intrinsic hyperpolarizabilities

We have investigated the electronic transition, chiroptical properties, and the second-order nonlinear optical (NLO) properties of eight novel chiral diborate compounds and elucidated structure–property relationships from the micromechanism. These compounds show calculated first hyperpolarizabilities (β) ranging from 2738.52 to 83976.45?×?10^?33?esu, which means that subtle structural modifications can substantially enhance the first hyperpolarizability. The cooperativity of intramolecular charge transfer and an effective way to enhance the NLO response were also systemically investigated. The linear correlation between the first hyperpolarizability and the inverse of the electronic transition energy suggests that the electronic transition energy plays a key role in determining the NLO response. These compounds have the potential to be excellent second-order NLO materials from the standpoint of the large β values, high transparency and the intrinsic non-centrosymmetry. The electronic transition and chiroptical properties have been assigned and analysed. The main UV–visible absorption features are best described as π?→?π* transitions. Moreover, the effects of different functionals and basis sets on the first hyperpolarizability were investigated.     

Monitoring molecular orientational order in NLO push–pull based polymeric films via photoacoustic measurements

The pulsed-laser photoacoustic-technique (PLPA) was implemented to characterize molecular orientational order and anisotropy in push–pull poled polymeric films as function of temperature and laser polarization. Traditionally, photoacoustic signals are considered to be directly proportional to the linear optical absorption in amorphous media. In this work, however, it is shown that photoacoustic signals can also be highly sensitive to the material anisotropy when convenient polarization dependent photoacoustic analyses are performed. Thus, variation of the molecular orientation in organic films, comprising rod-like polar chromophores, can be unambiguously monitored via rms-analyses performed on the amplitude of the generated opto-acoustical PLPA-signals as function of the incident laser polarization. This result can be useful for the characterization of organic-based nonlinear optical (NLO) poled films and, in general, in studies of anisotropic materials. In fact, in this work we were able to accurately determine the molecular order parameter (?) of a NLO-active spin-coated polymeric film containing optically active push–pull chromophores. These molecules, previously oriented via an electrical-poling procedure, are capable to exhibit strong second harmonic generation (SHG) effects. The PLPA-measurements were systematically compared to the linear UV–vis optical absorbance spectra while heating the poled film sample in order to monitor the thermally induced molecular disorder, so that the order parameter may be photo-acoustically evaluated via the PLPA-signals generated from the poled to the unpoled film phase. These PLPA-experiments were performed taking into account the UV–vis reference spectra for calibration and comparison purposes in the evaluation of the order parameter. A significant advantage of the PLPA-technique over commonly used optical spectral methodologies is its convenient applicability in samples exhibiting poor or null optical transmission.     

NLO characteristics of D-π-A coumarin-thiophene bridged azo dyes by Z-scan and DFT methods

ABSTRACT

The structural, electronic, intramolecular charge transfer (ICT) and nonlinear optical (NLO) properties of the donor-π-acceptor (D-π-A) azo linked dyes bearing coumarin thiophene bridge with different acceptors were inspected by Z-scan and DFT methods. The dye 3a exhibits bathochromic absorption maxima (649 and 650?nm) in the near IR region in DMF and DMSO. The dye 3a holds low HOMO–LUMO gap elucidated by CV and DFT indicating strong ICT character. The thermal stability is high for 3a and it shows enhanced NLO property by Z-scan and DFT methods as predicted in both global and range-separated hybrid functionals. The molecular geometry was optimised using B3LYP/6-311?+?g(d,p). The ICT characteristics are correlated with NLO properties obtained by Z-scan and DFT techniques.     

Anisotropy of electrooptical interaction in LiNbO3 crystals

Results of studying the conditions for optimum electrooptical (EO) interaction in lithium niobate crystals are presented. Analytical formulas are obtained for calculating refractive indices of natural waves and their polarizations for basis X-, Y-, and Z-cuts of crystals for arbitrary orientations of the wave vector of an optical wave. Conditions are found for the appearance of intermode EO interaction causing the orientation of polarization plane of natural waves to become a function of the external electric field.     

Nonlinear optical ferroelectric liquid crystals and device configurations

Ferroelectric Liquid Crystals (FLCs) are presented which comprise charge-transfer functional groups, such that highly efficient NonLinear Optical (NLO) properties and pronounced ferroelectricity result. By operating the NLO-FLCs in one of the two Bistable states of the Short-pitch Ferroelectric (SPF) conformation, stable, planar waveguides result. The NLO-FLCs exhibit exceptionally large second-order NLO-coefficientsd ₂₂ = 5 pm/V. Moreover, their linear electrooptical effect is shown to be essentially electronic in nature. This renders ultrafast electrooptical modulators with NLO-FLCs feasible.     

The role of the spontaneous electrooptical effect in the formation of electroholographic properties of strontium barium niobate crystals

The possibility of usage of the spontaneous electrooptical (EO) effect in strontium barium niobate (SBN) crystals for the creation of controlled electroholographic elements is studied. It is found that unipolar EO properties of these crystals with respect to switching their spontaneous polarization make it possible to devise field-controlled holographic elements with reversible energy-independent memory for spatial position of an optical beam.     

Study of an organic nonlinear optical material for nanoscale data storage by scanning tunneling microscope

In this paper, organic thin films of a nonlinear optical (NLO) material ((E)-1-ferrocenyl-2-(l-methyl-4-pyridiniumyl) ethylene iodide) were prepared by a vacuum deposition method. The typical I–V curve of the film exhibits a favorable room-temperature bistability. Further recording experiments have been performed with a scanning tunneling microscope, which confirmed that the thin film of the donor–π–acceptor NLO material could certainly be applied for nanoscale data storage. The average size of the recorded marks is about 1.5 nm. Mechanism analyses suggest that the formation of the recording dots is due to the local change of electrical property of the thin film, and the intermolecular charge transfer induced by an electric field is proposed as the reason for the change. PACS 68.37.-d; 73.61.-r; 81.16.Rf; 68.37.Ef; 73.61.Ph     

可用于电光材料的新型非线性光学活性的玻璃分子

通过在枝化苯胺-吡咯啉发色团接入具有π-π作用的葸官能团,设计并合成了一种可用于二阶非线性光学材料的新型树枝状玻璃分子发色团ETO和ETF.所得到的分子玻璃发色团具有良好的自成膜性能,其玻璃化温度测得分别为41℃(ETO)和39℃(ETF),用SHG法测得薄膜的非线性电光系数(d33)分别为38,32 pm/V.结果表...     

聚苯乙烯芪盐L—B膜的二阶非线性光学性质研究

首次合成了一种称之为聚苯乙烯芪盐的有机高分子材料.此材料可以在水面上形成稳定的单分子层膜,并且所形成的单分子层膜可以转移到固体衬底上去.对聚苯乙烯芪盐单分子层膜进行光学二次谐波产生测量,得到聚苯乙烯芪盐对应于每个发色团的二阶非线性极化率为1.2×10~(-28)esu.制备了该材料两种不同类型的多层膜,讨论了多层膜二次谐波产生信号不随层数增加而增加的可能原因.     

Closed loops theory on the third-order nonlinear optical property of α- and β- isomers of [M8O26]4−: a TDDFT study

The third-order nonlinear optical (NLO) property of the α- and β- isomers of [Mo₈O₂₆]^4? polyoxometallate ion were studied by DFT/TDDFT method. The second static hyperpolarisabilities, γ_iiii, γ_iijj and γ_mean were calculated by finite-field method as an extension of the usual DFT run, and the results suggest that without any ligands coordinated, the two isomer molecules in high symmetry own modestly large γ values (γ_mean ～5×10^?32esu, 3×10^?32esu, respectively), and the electronic properties of the two isomers were also studied by DFT method for the discussion of the origination of the NLO response, especially the unique effect of the molecular orbital ‘closed loops' on the NLO response.     

Theoretical study on the spectroscopic and third-order nonlinear optical properties of two-dimensional charge-transfer pyrazine derivatives

In this paper, density functional theory method was employed to study the electronic absorption spectrum and electronic static second hyperpolarisability of X-shaped pyrazine derivatives with two-dimensional charge-transfer structures. Computational results show that the push–pull electron abilities of the substituent groups and the length of the conjugated chains affect the electronic spectrum and static second hyperpolarisability of the pyrazine derivatives. As the push–pull electron abilities of the substituent groups or the length of the conjugated chains increases, the frontier molecular orbital energy gap decreases, resulting in increased second hyperpolarisability and redshift of the electronic absorption bands. The electronic absorption spectra of the pyrazine derivatives maintain good transparency in the blue light band. The electronic static second hyperpolarisability exhibits a linear relationship to the frontier molecular orbital energy gap. Particularly, increasing/decreasing the push–pull electron abilities of the substituent groups considerably affect the static second hyperpolarisability in long conjugated systems, which is important to the modulation of molecular organic nonlinear optical (NLO) properties. The studied pyrazine derivatives show large third-order NLO response and good transparency in the blue light band and are thus promising candidates as NLO materials for photonics applications.     

KBn(n=1~10)团簇的结构和性质的密度泛函理论研究

应用密度泛函理论(DFT) B3LYP方法在6-311+G(d)水平上计算并分析了KBn(n=1~10)团簇的几何结构及电子性质和极化率.通过研究团簇的平均结合能、能级间隙、二阶能量差分分析了团簇的稳定性规律,研究表明: KBn(n=1~10)团簇基态多数为立体构型,能级间隙和二阶能量差分结果表明KB3与KB9是幻数团簇.对团簇基态的极化率研究表明KBn团簇的电子结构随B原子的增加趋于紧凑,基本形成了一定的堆积方式.静态第一超极化率研究表明KB8与KB4两种平面构型的团簇具有较好的非线性光学性能.     

Synthesis and Characterization of Nonlinear Optical Polymers Containing Carbazole and Disperse Red Dye

Dye‐containing nonlinear optical (NLO) polymers were synthesized: (1) poly(3‐(2‐(3‐(2‐isocyanatopropan‐2‐yl)phenyl)‐2‐methylpropyl)‐4‐methyl‐1‐phenylpyrrolidine‐2,5‐dione), P[(DR1,Cz)MSt‐PMI], and (2) poly(9‐vinyl‐9H‐carbazole‐co‐disperse red 1), PAV[DR1‐Cz]. The synthesized NLO polymers were characterized by ¹H‐NMR, IR, and UV–VIS spectroscopy; differential scanning calorimetry (DSC); and thermogravimetric analysis (TGA). The electro‐optic (EO) coefficients (r₃₃) and their NLO properties were evaluated by simple reflection and the Maker fringe method. The EO coefficients of P[(DR1,Cz)MSt‐PMI] and PAV[DR1‐Cz] were measured at 632.8 nm to be 106 and 46.6 pm/V, respectively. The second harmonic generation (SHG) coefficient (d₃₃) of P[(DR1,Cz)MSt‐PMI] was measured to be 71.25 pm/V.     

Spectroscopic analysis,AIM, NLO and VCD investigations of acetaldehyde thiosemicarbazone using quantum mechanical simulations

The prepared Acetaldehyde thiosemicarbazone (ATSC) have been investigated by both the experimental and theoretical methods; through this work, the essentiality of elucidation of molecular fragments source linear and non-linear optical properties was explored. The stability of the structure and entire calculations have been performed on HF and B3LYP methods with 6-311++G(d,p) level of basis set. The Mulliken charge profile, electronic, optical and hyper polarizability analyses have been carried out in order to evaluate nonlinear optical (NLO) performance of the present compound. The exact optical location of the ATSC was determined by executing UV–Visible calculations on TDSCF method. The existence of the molecular group for the inducement and tuning of NLO properties were thoroughly investigated by performing fundamental vibrational investigation. The optical energy transformation among frontier molecular levels has been described in UV–Visible region. The Gibbs energy coefficient of thermodynamic functions was monitored in different temperature and it was found constant irrespective of temperatures. The appearance of different chemical environment of H and C was monitored from the ¹H and ¹³C NMR spectra. The vibrational optical polarization characteristics with respect to molecular composition in the compound have been studied by VCD spectrum. The bond critical point, Laplacian of electron density, electron kinetic energy density and total electron energy density have calculated and analysed using AIM study.     

Direct femtosecond laser fabrication of antireflective layer on GaAs surface

Photoinduced linear electrooptical (EO) effect was studied for Zinc oxide nanofilms doped by Nd. We have chosen Nd rare earth impurity with different contents to explore its influence on photoinduced EO. The kinetics of the photoinduced EO changes was studied. We have chosen the bicolor coherent 10 ns Nd:YAG laser pulses with power densities varying up to about 1 GW/cm² as the photoinducing beam. The enhancement of the photoinduced liner EO and its relaxation was explored. Additionally, the study of the photoinduced trapping levels within the energy gap was performed and the explanation of the obtained results is given.     

Investigation of a new electro-optical guest–host polyetherketone polymer films

The polyetherketone (PEK-c) guest–host system thin films in which the range of the weight percent of 3-(1,1-dicyanothenyl)-1-phenyl-4, 5-dihydro-1H-pyrazole (DCNP) is from 20% to 50% were prepared. Their corona poling temperatures were optimized by using the in situ second-harmonic generation (SHG) measurement. The high predicted value of electro-optical (EO) coefficient γ₃₃=48.8 pm/v by using two-level model was obtained when the weight percent of DCNP in the polymer system is 40%, but EO coefficients are attenuated at higher chromophore loading than 40%. The temporal stability of the EO activity of the guest–host polymer was evaluated by probing the decay of the orientational order of the chromophores in the polymer system.