含有噻唑生色团的Y-型有机分子的二阶非线性光学性质

采用密度泛函理论(DFT)B3LYP/6-31G*方法优化了一系列含有噻唑生色团的Y-型有机杂环分子的几何构型, 在此基础上结合有限场(FF)方法和含时密度泛函理论(TD-DFT)对分子的非线性光学(NLO)活性和电子光谱进行计算分析. 结果表明, 这些分子具有A-π-D-π-A(A: 受体, D: 给体)结构, 分子基态偶极矩、极化率和二阶NLO系数(β)随支链共轭桥的增长及生色团共轭效应的增大而增大. 同时, 该系列有机杂环分子的二阶极化率总的有效值(βtot)与其前线分子轨道能级相关, 分子的前线分子轨道能级差越小, βtot值越大.     

Organic sol-gel materials for second-order nonlinear optics based on melamines

A series of all organic nonlinear optical (NLO) sol-gel materials based on melamines and an azobenzene dye (Disperse Orange 3; DO3) have been investigated. Different contents of DO3 were covalently bonded with the melamine-based organic network via condensation of amino and methylol groups. The optically clear samples exhibited second-order optical nonlinearity (second-harmonic coefficient d₃₃) = 35.4 and 11.5 pm/V at 1064 and 1542 nm, respectively) after poling and curing at 220°C for 1 h. Thermal behavior of these organic NLO sol-gel systems was studied by temperature-dependent dielectric relaxation. The results indicate that the incorporation of rigid NLO-active chromophore into the melamine-based matrix leads to high rigidity and dense packing of the organic network. Subsequently, higher glass transition temperatures were obtained for the organic NLO sol-gel material with higher DO3 content. The influence of composition on the temporal stability at 100°C was also investigated. Temporal stability at 100°C was studied as a function of system composition. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2503–2510, 1999     

[C5H12N]SnCl3: A Tin Halide Organic–Inorganic Hybrid as an Above-Room-Temperature Solid-State Nonlinear Optical Switch

Nonlinear optical (NLO) switches driven by a solid-state structural phase transition have attracted extensive attention; however, above-room-temperature solid-state NLO switch materials are still sparse. Herein, we report an above-room-temperature tin halide organic–inorganic hybrid quadratic NLO switchable material, N-methylpyrrolidinium trichloride stannite ([C₅H₁₂N]SnCl₃, MPSC). The MPSC crystal exhibits a phase-matchable NLO property that is 1.1 times that of KH₂PO₄ (KDP) and NLO switching behavior, changing from a high second harmonic generation (SHG) response to a low SHG response at 383 K, thereby demonstrating its prospective applications in the field of nonlinear optics. Variable-temperature crystal structural analysis combined with theoretical calculations revealed that the large NLO response stems from the inorganic SnCl₃ moiety, whereas the high-performance NLO switching properties mainly originate from the order/disorder transformation of the N-methylpyrrolidinium. This work provides a new approach to designing and exploring new high-performance quadratic NLO switches involving tin halide organic–inorganic hybrids.     

Magneto-chiral Nonlinear Optical Effect with Large Anisotropic Response in Two-Dimensional Halide Perovskite

The chiral organic–inorganic halide perovskites (OIHPs) are vital candidates for superior nonlinear optical (NLO) effects associated with circularly polarized (CP) light. NLO in chiral materials often couples with magnetic dipole (MD) transition, as well as the conventional electric dipole (ED) transition. However, the importance of MD transition in NLO process of chiral OIHPs has not yet been well recognized. Here, the circular polarized probe analysis of second harmonic generation circular dichroism (SHG-CD) provides the direct evidence that the contribution of MD leads to a large anisotropic response to CP lights in chiral OIHPs, (R-/S-MBACl)₂PbI₄. The thin films exhibit great sensitivity to CP lights over a wide wavelength range, and the g-value reaches up to 1.57 at the wavelength where the contribution of MD is maximized. Furthermore, it is also effective as CP light generator, outputting CP-SHG with maximum g-factor of 1.76 upon the stimulation of linearly polarized light. This study deepens the understanding of relation between chirality and magneto-optical effect, and such an efficient discrimination and generation of CP light signal is highly applicable for chirality-based sensor and optical communication devices.     

Effect of chelating agent (1,10-phenanthroline) on potassium hydrogen phthalate crystals

The influence of a new organic additive, chelating agent 1,10-phenanthroline (Phen) (∼5.0·10⁻³ M L⁻¹) on potassium hydrogen phthalate (KHP) single crystals at 30° is investigated. The crystals were grown from the aqueous solutions of pH ∼4.5 at constant temperature by solvent evaporation technique. The chelating agent leads to an increase in metastable zone width and assists the bulk growth process. The growth rate of crystals in the presence of Phen decreases considerably with an increase in impurity concentration. Not much variation is observed in FTIR and cell parameter values, determined by XRD analysis. It appears that the growth promoting effect (GPE) of Phen is caused by the adsorption of the organic additive on the prism of KHP crystals. Differential scanning calorimetry (DSC) and TG-DTA studies reveal the purity of the sample and no decomposition is observed up to the melting point. Scanning electron microscope (SEM) photographs exhibit the effectiveness of the impurity in changing the surface morphology of KHP crystals. Contrary to expectations, Phen depresses the NLO efficiency of KHP, suggesting that the molecular alignments in the presence of Phen results in cancellation effects disturbing the non-linearity.     

MOF-Templated Synthesis of Ultrasmall Photoluminescent Carbon-Nanodot Arrays for Optical Applications

Arrays of ultrasmall and uniform carbon nanodots (CDs) are of pronounced interest for applications in optical devices. Herein, we describe a low-temperature calcination approach with rather inexpensive reactants. After glucose molecules had been loaded into the pores of metal–organic frameworks (MOFs), well-defined CD arrays were produced by heating to 200 °C. The size and spacing of the CDs could be controlled by the choice of templating MOF: HKUST-1, ZIF-8, or MIL-101. The sizes of the obtained CDs were approximately 1.5, 2.0, and 3.2 nm, which are close to the corresponding MOF pores sizes. The CD arrays exhibited interesting photophysical properties, including photoluminescence with tunable emission and pronounced nonlinear optical (NLO) effects. The NLO properties of the obtained CD arrays were significantly different from those of a CD suspension, thus indicating the existence of collective phenomena.     

PREPARATION AND SECOND-ORDER OPTICAL NONLINEARITY OF NOVEL PHENOXYSILICON NETWORKS BY SOL-GEL PROCESS**

 Four phenoxysilicon networks for nonlinear optical (NLO) applications were designed and prepared by an extended sol-gel process without additional H₂O and catalyst. All poled polymer network films possess high second-order nonlinear optical coefficients (d₃₃) of 10-?～10-8 esu. The investigation of NLO temporal stability at room temperature and elevated temperature (120℃) indicated that these films exhibit high d33 stability because the orientation of the chromophores are locked in the phenoxysilicon organic/inorganic networks.     

Organic nonlinear optical materials: where we have been and where we are going

Nonlinear optical (NLO) materials can be useful for a variety of applications varying from modulation of optical signals facilitated by the electro-optic effect-the effect whereby the refractive index of a material changes in response to an applied electric field-to microfabrication, sensing, imaging, and cancer therapy facilitated by multiphoton absorption, wherein molecules simultaneously absorb two or more photons of light. This short Focus article is a brief personal perspective of some of the key advances in second-order NLO materials and in multiphoton-absorbing materials, and of how and why these advances have led to renewed interest in organic NLO materials.     

SYNTHESIS AND OPTICAL PROPERTIES OF A NOVEL ORGANIC/INORGANIC HYBRID NONLINEAR OPTICAL POLYMER VIA SOL-GEL PROCESS*

A new organic/inorganic hybrid nonlinear optical (NLO) material was developed by the sol-gel process of analkoxysilane dye with tetraethoxysilane. A NLO moiety based on 4-nitro-4'-hydroxy azobenzene was covalently bonded tothe triethoxysilane derivative, i.e. γ-isocyanatopropyl triethoxysilane. The preparation process and properties of the sol-gelderived NLO polymer were studied and characterized by SEM, FTIR, ~1H-NMR, UV-Vis, DSC and second harmonicgeneration (SHG) measurement. The results indicated that the chemical bonding of the chromophores to the inorganic SiO_2networks induces low dipole alignment relaxation and preferable orientational stability. The SHG measurements also showedthat the bonded polymer film containing 75 wt% of the akoxysilane dye has a high electro-optic coefficient (r_(33)) of 7.1 pm/Vat 1.1 μm wavelength, and exhibit good SHG stability, the r_(33) values can maintain about 92.7% of its initial value at roomtemperature for 90 days, and can maintain about 59.3% at 100℃ for 300 min.s     

六元碳环邻位对称取代的Λ-型分子非线性光学系数的计算

采用密度泛函理论(DFT)的BHandHLYP/6-31G*方法,对3类含有六元碳环的Λ-型分子的几何构型进行优化.在优化结构的基础上,结合有限场方法(FF)和含时密度泛函理论(TD-DFT)对分子的二阶非线性光学(NLO)活性及电子吸收光谱进行研究.结果表明,在拐点处环己烷的构象不同时,分子电荷分布、偶极矩、极化率、二阶NLO系数和电子吸收光谱等变化很小.以苯环为拐点片段的分子有所不同,当支链取代基R增大时,以苯环为拐点片段分子的极化率和二阶NLO系数增加明显.     

Tailoring the donor moieties in TPA-based organic dyes for efficient photovoltaic,optical and nonlinear optical response properties

The current study reports tailoring the electronic donor structures of organic dyes to modify their optical and nonlinear optical (NLO) response properties. Five (5) tri-phenyl amine (TPA) based Donor-π-Acceptor (D-π-A) organic dyes with the codes ICAA1 , ICAA2 , ICAA3 , ICAA4 , and ICAA5 were designed and investigated for their optical and NLO properties using quantum chemical methods. Optical and NLO properties of these dyes were studied by CAM-B3LYP method and 6-311G* basis set. The focus has been on the impact of adding secondary donors and shifting their substitutions at ortho (o), meta (m) and para (p) positions. Among all designed compounds, ICAA4 showed the highest amplitude of average third-order NLO polarizability <γ>, which is calculated to be 1316 × 10⁻³⁶ esu. Time-dependent Density Functional Theory (TD-DFT) method was used to determine how a change in the position of the donor affected the excitation energy (E_g) and NLO response properties. The findings showed that changing the position of the secondary donor results in a red shift among absorption spectra as well as the increase in their NLO responses. Complete process of intramolecular charge transfer (ICT) has been investigated in terms of different optical parameters such as frontier molecular orbitals (FMOs), molecular electrostatic potentials (MEPs), transition density matrix (TDMs), density of states (DOS), electron density difference (EDD), and natural bond orbital (NBO) analysis. Our calculations for study of ICT process indicate that p-position of methoxy group performs better among all other positions and even it has better NLO response properties than the compound with three collective methoxy groups. The calculated V_oc values of all designed molecules range from 1.09 to 1.30, all of them are positive while their ΔG_inject is found to be in the range of −0.87 to −1.79 eV indicating their decent potential for photovoltaic applications. The studied optical, NLO and photovoltaic parameters illustrated that ICAA1 to ICAA5 are appropriate molecules not only for NLO applications but also for efficient photovoltaic purposes.     

Design and synthesis of interpenetrating polymer networks for second-order nonlinear optics

There has been a tremendous recent interest in the development of second-order nonlinear optical (NLO) polymeric materials for photonic applications. However, a major drawback of second-order NLO polymers that prevents them from being used in device applications is the instability of their electric field induced dipolar alignment. The randomization of the dipole orientation leads to the decay of second-order optical nonlinearities. Numerous efforts have been made to increase the stability of the second-order NLO properties of polymers. The search for new approaches to develop NLO polymers with optimal properties has been an active research area since the past decade. A novel approach, combining the hybrid properties of high glass transition temperatures, extensively extensively crosslinked networks and permanent entanglements, based on interpenetrating polymer networks (IPN) is introduced to develop stable second-order NLO materials. Two types of IPN systems are prepared and their properties are investigated. The designing criteria and the rationale for the selection of polymers are discussed. The IPN samples show excellent temporal stability at elevated temperatures. Long-term stability of the optical nonlinearity at 100°C has been observed in these materials. Temporal stability of the NLO properties of these IPNs is synergistically enhanced. Relaxation behavior of the optical nonlinearity of an IPN system has been studied and compared with that of a typical guest/host system. The improved temporal stability of the second-order NLO properties of this IPN system is a result of the combination of the high rigidity of the polymer backbones, crosslinked matrices and permanent entanglements of the polymer networks. A slight modification of the chemical structure resulted in an improvement of the optical quality of the sample.     

含对硝基偶氮苯胺生色团的键合型有机/无机复合材料的合成及其二阶非线性光学特性

以γ 缩水甘油氧丙基三甲氧基硅烷 (KH5 6 0 )作中间体 ,用溶胶 凝胶 (Sol Gel)法合成了含对硝基偶氮苯胺 (DO3)生色团的新型键合型有机 /无机复合非线性光学 (NLO)材料 ,在这种有机生色团与无机玻璃键合形成的交联网络结构中 ,无机玻璃的刚性三维结构和优良的高温稳定性能有效抑制NLO生色团的极化松弛 .二次谐波信号 (SHG)测量表明 ,合成的键合型聚合物膜的二阶非线性光学系数 (d33)值达 5 79× 10 -7esu ,NLO稳定性也较好 ;在室温下放置 90天后 ,其d33 值能维持初始值的 93 5 % ;在 10 0℃下放置 30 0min后 ,其d33 值仍能维持初始值的 6 0 %     

有机二阶非线性光学发色团的研究进展

近年来,科学家们通过引进杂环片段、采用双(或多)官能化以及运用分子间弱相互作用等方法,在二阶非线性光学发色团的性能优化方面取得了较大进展.结合本课题组的研究,对此领域的研究进行了较全面的综述,并特别针对“非线性-透光性”矛盾的解决途径进行了较为详细的介绍.     

Enhanced third‐order nonlinear optical properties determined in thin films using the Z‐scan technique: bis(μ‐4,4′‐oxydibenzoato)bis[(4′‐phenyl‐2,2′:6′,2′′‐terpyridine)cobalt(II)]

π‐Conjugated organic materials exhibit high and tunable nonlinear optical (NLO) properties, and fast response times. 4′‐Phenyl‐2,2′:6′,2′′‐terpyridine (PTP) is an important N‐heterocyclic ligand involving π‐conjugated systems, however, studies concerning the third‐order NLO properties of terpyridine transition metal complexes are limited. The title binuclear terpyridine Co^II complex, bis(μ‐4,4′‐oxydibenzoato)‐κ³O,O′:O′′;κ³O′′:O,O′‐bis[(4′‐phenyl‐2,2′:6′,2′′‐terpyridine‐κ³N,N′,N′′)cobalt(II)], [Co₂(C₁₄H₈O₅)₂(C₂₁H₁₅N₃)₂], (1), has been synthesized under hydrothermal conditions. In the crystal structure, each Co^II cation is surrounded by three N atoms of a PTP ligand and three O atoms, two from a bidentate and one from a symmetry‐related monodentate 4,4′‐oxydibenzoate (ODA²⁻) ligand, completing a distorted octahedral coordination geometry. Neighbouring [Co(PTP)]²⁺ units are bridged by ODA²⁻ ligands to form a ring‐like structure. The third‐order nonlinear optical (NLO) properties of (1) and PTP were determined in thin films using the Z‐scan technique. The title compound shows a strong third‐order NLO saturable absorption (SA), while PTP exhibits a third‐order NLO reverse saturable absorption (RSA). The absorptive coefficient β of (1) is −37.3 × 10⁻⁷ m W⁻¹, which is larger than that (8.96 × 10⁻⁷ m W⁻¹) of PTP. The third‐order NLO susceptibility χ⁽³⁾ values are calculated as 6.01 × 10⁻⁸ e.s.u. for (1) and 1.44 × 10⁻⁸ e.s.u. for PTP.     

A study of structural effects on linear and nonlinear response of bicompartmental Ni (II) Schiff base complexes

Herein we investigate imaginary third order NLO activity, optical limiting capability and first hyperpolarizabilities of five Ni (II) salen complexes using experimental and theoretical methods. The complexes are tuned to have different NLO response by changing mainly the diimine spacer group. Out of the compounds reported, the one with o‐phenylene spacer group exhibits the highest NLO activity comparable with that of polymers and semiconductors which is followed by the compound with ethylene spacer unit. The order of activity is a direct function of the degree of π‐delocalization. Further all the tested compounds returned outstanding optical limiting capabilities making them excellent materials for fabrication of such devices. The experimental results were substantiated with frontier orbital calculations carried out using DFT at M06/6‐31G* level of theory and complex with aromatic spacer group exhibits least energy gap and highest activity. The total dipole moment, polarizability and first hyperpolarizability were also calculated at the same level of theory which are also in line with the experimentally observed results.     

Preparation of stable second‐order nonlinear optical films by sol–gel technique

A stable nonlinear optical (NLO) film containing “T” type alkoxysilane dye was prepared by sol–gel technology. This crosslinked “T” type alkoxysilane dye was synthesized and fully characterized by FTIR, UV–Vis spectra, and ¹H‐NMR. Followed by hydrolysis and copolymerization processes of the alkoxysilane with γ‐glycidoxypropyl trimethoxysilane (KH560) and tetraethoxysilane (TEOS), high quality inorganic–organic hybrid second‐order NLO films were obtained by spin coating. The “T” type structure of the alkoxysilane was found to be effective for improving the temporal stability of the optical nonlinearity due to the reduction in the relaxation of the chromophore in the film materials. Copyright © 2009 John Wiley & Sons, Ltd.     

Nonlinear Optical Response of a Polymer Electret with Incorporated Organic Chromophores

An analytical approach aimed at modeling the nonlinear optical (NLO) response of a polymer electret with incorporated organic dipole chromophores is extended to the dynamic case. The approach allows the effect of the locally anisotropic, polarizable, deformable polymer matrix on the chromophore NLO response to be accounted for. The method exploits the original cavity ansatz according to which the virtual cavity occupied by the chromophore in the polymer matrix is chosen to be conformal to the characteristic ellipsoid of the generalized permittivity tensor. Analytical expressions for the dynamic electric moments of dipole chromophores and macroscopic polarization of a polymer electret at fundamental and second harmonic frequencies are obtained by using a computational scheme based on two self‐consistency procedures. On the basis of the expressions for dynamic macroscopic polarization, the analytical formulas for linear, ${\chi _j^{i(1)} (\omega )}$ , and quadratic, ${\chi _{jk}^{i(2)} (2\omega )}$ , electric susceptibilities are obtained. The presented expressions establish the relationship between the molecular polarizabilities of chromophores and the macroscopic electrical properties of the polymer electret.     

Two Covalent Ultraviolet Nonlinear Optical Crystals

Nonlinear optical (NLO) crystals are the vital components of laser science and technology, as they can convert lasers in common wavelengths into new wavelength bands for ultraviolet (UV), IR, and even terahertz laser output. Known UV NLO crystals mainly focus on crystals containing cations, but covalent crystals have rarely been reported. Here we report two covalent NLO crystals, B₂O₃ I and B₂O₃ II. According to the first‐principles calculations, B₂O₃ I and II have extremely short absorption edges of about 134 nm and 141 nm, large NLO coefficients of d₂₂=1.38 pm/V and d₂₄=0.702 pm/V, as well as sufficient birefringences of 0.037 and 0.031, respectively. Notably, the absorption edges are almost the shortest among NLO crystals. Meanwhile, the NLO coefficients are evidently larger than that of another well‐known covalent NLO crystal α‐SiO₂ and are comparable to those of the commercial UV NLO crystal LiBO₃ with Li⁺ cation. Furthermore, the birefringences are significantly larger than that of α‐SiO₂, which are favorable to the phase matching for both crystals. These results reveal that B₂O₃ I and B₂O₃ II are excellent candidates for UV NLO applications. In‐depth calculations are carried out to reveal the origin of excellent NLO properties. These covalent crystals provide a new direction for the research of UV NLO crystals.     

Nonlinear optical polyimides consisting of chromophore‐containing dendrons with site‐isolation effect

To investigate the dendritic structure effects on the electro‐optical (EO) coefficients and thermal stability of the nonlinear optical (NLO) active materials, a bifunctional compound, IDD (4‐isocyanato‐4′(3,3‐dimethyl‐ 2,4‐dioxo‐acetidino)‐diphenylmethane) was used as a building block to synthesize a series of novel NLO chromophore‐containing dendritic structures including Generation 0.5 (G0.5) to Generation 3 (G3). The glass transition temperatures (T_g) of G1–G3 dendrons were in the range of 76–116°C, whereas only the G0.5 dendron exhibited a melting temperature (T_m), 98°C. Moreover, a series of NLO‐active guest–host systems ranging from polyimide‐G0.5 (PI‐G0.5) to polyimide‐G3 (PI‐G3) were prepared by blending 20 wt% chromophore‐containing dendron with a high T_g polyimide. EO coefficients ranged from 6.1 to 12.9 pm/V. The r₃₃/dye content ratio increased with increasing generation of dendron‐containing polyimide samples. Particularly, the improvement in r₃₃/dye content ratio of PI‐G2.5 sample tripled as compared to that of the guest–host sample with Disperse Red 1. Excellent temporal stability of PI‐G0.5 and PI‐G1.5 at 80°C was obtained. Moreover, waveguide properties for NLO polymers containing higher generation dendrons (3.1–3.6 dB/cm at 830 nm) were also obtained. Copyright © 2008 John Wiley & Sons, Ltd.