非线性光学有机晶体材料的研究进展

随着科技的进步和时代的发展,光电子技术将是21世纪的核心技术之一.对于光电子技术的发展,非线性光学材料,尤其是非线性光学晶体是不可缺少的关键材料.本文主要从分子设计方面概述了阴阳离子二元生色团体系、纯有机分子、纳米晶体和有机金属复合物等几种主要的非线性光学有机晶体材料的研究情况,并对其各自的特点做了简单的说明.     

基于分子间侧向氢键作用的电光材料制备及性能

通过重氮耦合和酯化等反应制备了一系列侧向含有酰胺基团的偶氮苯类非线性光学生色团, 并将其与聚合物进行掺杂或通过分子间的侧向氢键作用制备了主客体型及超分子型的电光薄膜材料. 生色团的结构通过核磁共振谱(¹H NMR, NMR)、 红外光谱(IR)、 质谱(MS)和元素分析(EA)等进行了表征, 结果表明, 生色团形成了分子间的氢键作用. 通过紫外-可见(UV-Vis) 光谱研究了材料的极化性能. 相比主客体型电光薄膜材料, 由分子间侧向氢键作用形成的超分子型电光薄膜材料无需与聚合物基体材料复合, 更有利于提高材料的生色团含量、 极化取向度及稳定性. 通过Teng-Man简单反射法研究了主客体型和超分子型电光材料的二阶非线性光学性质, 结果表明, 基于分子间侧向氢键作用形成的超分子体系具有更大的电光系数.     

So1-Gel法制备键合型有机/无机复合非线性光学材料

以含对硝基苯胺生色团的烷氧基硅烷染料和正硅酸乙酯为原料,通过溶胶-凝胶法合成了含对硝基苯胺生色团的键合型有机/无机复合非线性光学材料.在这种有机生色团与无机玻璃键合形成的交联网络中,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非线性光学生色团的极化松弛.二阶谐波信号(SHG)测量表明,这种有机/无机复合材料的二阶非线性光学系数(d33)值达到4.62 × 10-8esu;NLO稳定性也较好;室温下90d后d33值维持初始值的84.5%,100℃下放置300min后d33值维持初始值的51%.     

一种含稀土半菁的二阶非线性光学材料的研究

LB膜技术作为一种重要手段，可以在分子水平上对材料进行组装．有机化合物作为非线性光学材料，由于具有很大的非线性系数、光学响应速度快及光损伤阈值大等优点而受到人们的重视[1]．对于二阶非线性光学材料而言，其发色团分子的非中。心对称结构是其非线性光学信号叠加的必要条件．LB膜技术以其不同的沉积方式，可有效地控制有机分子的排列和取向，形成非中，心对称结构，成为制备高性能二阶非线性光学材料的良好手段．我们首先将疏水性的稀土配阴离子引入非线性光学成膜材料中，由于其体积较大，可以避免对形成LB膜不利的H聚体的生成…     

二阶非线性光学聚合物材料

非线性光学材料是一类具有很高实用价值的功能材料。综述了聚合物二阶非线性光学材料的研究、极化聚合物在实用化研究方面取得的新进展,介绍了提高极化聚合物生色团高温取向稳定性、设计合成光损失较小的生色团以及优化聚合物主体的新方法。     

有机二阶非线性光学聚合物的研究进展

非线性光学材料在激光、光通信、光处理、高频电光器件及太赫兹等方面具有重要的应用。相比传统无机非线性光学材料,有机二阶非线性光学材料具有电光系数高、响应速率快、易加工等优点。近年来,基于有机非线性光学材料的研究成为热门领域,高频电光器件、太赫兹器件等都受到了业内广泛关注。本文综述了不同种类的有机二阶非线性光学材料的研究进展和未来的发展方向。此类材料的电光性能和取向稳定性可以通过分子设计策略和化学合成、发色团与聚合物的结构关系及掺杂技术等进行有效的调控,但是研发满足实际应用且综合性能优异的有机非线性光学材料仍面临诸多挑战。     

PUT/SiO2复合材料的制备与表征

利用溶胶-凝胶法将硅烷染料、含硅氧烷的非线性聚氨酯与正硅酸乙酯(TEOS)共水解, 缩合制备了新型聚氨酯噻唑(PUT/SiO2)纳米复合材料, 并用IR、SEM、TEM、UV-Vis、DSC和TGA对其结构和性能进行了表征. 结果显示, 材料中聚氨酯与SiO2以共价键相连, 没有发生相分离, 且其中非线性较好的噻唑生色团含量和材料的玻璃化转变温度(Tg)、热分解温度(Td)都较纯非线性光学材料(NLO)聚氨酯(PU)有显著增加, 可以用来制备性能优良的二阶非线性光学器件.     

多孔纳米氧化铝薄膜上荧光分子光谱特性研究

通过两步电化学阳极氧化技术制备了孔径为40nm的多孔纳米阳极氧化铝材料(AAO),在AAO薄膜上分别填充了几种有机荧光分子使其形成高度有序的有机-无机复合体发光阵列,测定了此复合体的发射光谱．结果表明,AAO薄膜对有机分子具有较强的结合能力,其结合能力来源于物理和化学的协同作用．在AAO纳米薄膜上的有机荧光分子的最大发射波长均产生了明显的蓝移现象,初步探讨了此现象的机理．有机分子填充进入高度有序的AAO纳米孔阵列之中时,有机分子的聚集形式会发生改变并且也是高度有序的,同时由于极化作用使有机分子沿着纳米孔的轴向具有相对优势的分子取向,使有机分子在AAO纳米薄膜上形成了接近单分子层的高度有序的排列方式,增强了发光效率．     

咪唑类二阶非线性光学活性分子的设计、合成及性能

设计、合成了两个新的咪唑类二阶非线性光学生色团，对其热性能、透明性和 二阶非线性光学性能进行了测定和研究，实验表明生色团为非线性光学性能-透明 性-热稳定性能综合优化的有机二阶非线性光学生色团。     

偶氮苯侧链结构对聚丙烯酸酯三阶非线性光学性能影响

设计合成了一系列含偶氮苯非线性生色团的丙烯酸酯,并采用溶液聚合法合成了功能化的聚丙烯酸酯,利用FTIR、NMR、UV等对化合物的结构进行了表征,证实得到了指定结构的化合物.利用Z扫描技术对合成的聚丙烯酸酯的非线性光学性能进行了研究,通过对聚合物的非线性光学吸收拟合,计算得到非线性吸收系数β和三阶非线性系数χ(3),并探讨了取代基生色团分子结构与高分子三阶非线性光学性能的关系,结果显示增大侧链生色团π电子离域长度或强DπA(推拉基团)结构均可有效提高聚合物的三阶非线性光学性能.     

Poled amorphous polymers for second-order nonlinear optics

Recent advances in poled amorphous polymers for second-order nonlinear optics are discussed with emphasis on stabilizing the frozen-in nonlinearity via chemical crosslinking under electric fields. Specific examples of a linear polymer and a crosslinked polymer, both with nitroaniline-type chromophores covalently attached as side groups, are presented and compared in their glass transition behavior, linear optical properties, poling dynamics, and stability of frozen-in nonlinearity. It is demonstrated that by employing chemical crosslinking under electric fields one can prepare highly efficient and stable poled polymers that exhibit no decay in nonlinearity at ambient conditions and no apparent tendency of decay even at 85°C as well as excellent optical properties. The historical development of organic materials for second-order nonlinear optics and recent advances in device fabrication based on poled polymers are also discussed briefly.     

The Appeal of Small Molecules for Practical Nonlinear Optics

Small organic molecules with a π-conjugated system that consists of only a few double or triple bonds can have significantly smaller optical excitation energies when equipped with donor and acceptor groups, which raises the quantum limits to the molecular polarizabilities. As a consequence, third-order nonlinear optical polarizabilities become orders of magnitude larger than those of molecules of similar size without donor-acceptor substitution. This enables strong third-order nonlinear optical effects (as high as 1000 times those of silica glass) in dense, amorphous monolithic assemblies. These properties, accompanied by the possibility of deposition from the vapor phase and of electric-field poling at higher temperatures, make the resulting materials competitive towards adding an active nonlinear optical or electro-optic functionality to state-of-the-art integrated photonics platforms.     

Dependence of the two-photon absorption cross section on the conjugation of the phenylacetylene linker in dipolar donor-bridge-acceptor chromophores

The nonlinear optical properties of four isomeric dipolar two-photon chromophores are compared. The chromophores consist of a carbazole electron donor coupled to a naphthalimide electron acceptor by a phenylacetylene bridge. By variation of the connectivity of the bridge at the phenyl groups, four compounds with 0, 1, and 2 meta linkages are synthesized. The linear and nonlinear optical properties of these compounds are measured. Despite similar linear absorption cross sections, the two-photon absorption cross section delta of the all-meta compound is almost a factor of 10 lower than the all-para compound. By taking the detailed molecular conformations into account in order to calculate accurate dipole moment changes, we find that the decrease in delta results largely from the decreased charge transfer ability with increasing number of meta linkages. We find that a two-state model can be used to predict semiquantitatively the observed trend in delta on the basis of the linear optical properties of the molecules. This work illustrates the dramatic effect the ground-state polarizability can have on the nonlinear optical response of organic compounds and also provides a way to quantify the ability of meta linkages to inhibit charge transfer in their ground-state configuration.     

聚合物非线性光学材料

最近,有机非线性光学材料已引起了人们极大的兴趣。一些可极化有机分子具有很大的分子超极化率,可惜,受晶体对称性的限制仅有少数晶体具有二阶非线性光学效应。极化聚合物可以产生统计非中心对称的环境,使材料的二阶特性显示出来。本文在简单介绍了有机非线性光学和极化的原理后,综述了聚合物二阶非线性光学材料的研究进展。此外,对聚合物的三阶非线性光学效应的研究也作了介绍。     

Organic Polymeric and Non-Polymeric Materials with Large Optical Nonlinearities

Nonlinear optical properties are a sensitive probe of the electronic and solid-state structure of organic compounds and as a consequence find various applications in many areas of optoelectronics including optical communications, laser scanning and control functions, and integrated optics technology. Because of their strongly delocalized π electronic systems, polymeric and non-polymeric aromatic compounds show highly nonlinear optical effects. Nowadays, polymer chemists are able to tailor specific materials properties for various applications. Some organic substances with π electronic systems exhibit the largest known nonlinear coefficients, often considerably larger than those of the more conventional inorganic dielectrics and semiconductors, and thus show promise for thin-film fabrication, allowing the enormous function and cost advantages of integrated electronic circuitry. The electronic origins of nonlinear optical effects in organic π electronic systems are reviewed, with special emphasis being given to second-order nonlinear optical effects. Methods for measuring nonlinear optical responses are outlined, and the critical relationships of the propagation characteristics of light to observed nonlinear optical effects and to solid-state structure are discussed. Finally, the synthesis and characterization of organic crystals and polymer films with large second-order optical nonlinearities are summarized.     

Chiral Side Groups Trigger Second Harmonic Generation Activity in 3D Octupolar Bipyrimidine‐Based Organic Liquid Crystals

The design of efficient noncentrosymmetric materials remains the ultimate goal in the field of organic second‐order nonlinear optics. Unlike inorganic crystals currently used in second‐order nonlinear optical applications, organic materials are an attractive alternative owing to their fast electro‐optical response and processability, but their alignment into noncentrosymmetric film remains challenging. Here, symmetry breaking by judicious functionalization of 3D organic octupoles allows the emergence of multifunctional liquid crystalline chromophores which can easily be processed into large, flexible, thin, and self‐oriented films with second harmonic generation responses competitive to the prototypical inorganic KH₂PO₄ crystals. The liquid‐crystalline nature of these chiral organic films also permits the modulation of the nonlinear optical properties owing to the sensitivity of the supramolecular organization to temperature, leading to the development of tunable macroscopic materials.     

2,2′‐Bipyridine‐Based Dendritic Structured Compounds for Second Harmonic Generation

Parallel alignment of dipolar electron‐donor–π‐bridge‐electron‐acceptor entities can strongly enhance their nonlinear optical properties. This favorable arrangement can be in principle achieved by linking these units covalently or through metal coordination. Four dipolar single‐strand chromophores decorated with a 5‐electron‐donor–5′‐electron‐acceptor‐modified 2,2′‐bipyridine functionality were synthesized. For two of these chromophores triple‐stranded dendritic structures were successfully formed. All of the compounds were characterized with respect to their linear and nonlinear optical properties. For the aldehyde derivatives an enhancement of the first hyperpolarizability of 4.5 rather than 3 was obtained when going from single to triple strands. Theoretical calculations with density functional theory suggest that interstrand transitions contribute to the optical properties of the dendritic structures.     

几种查耳酮的二阶非线性光学性质解析

合成了一系列的查耳酮衍生物,系统地测量了其ＳＨＧ（二次谐波产生）效率和截止吸以长,并用ＣＮＤＯ／Ｓ－ＣＩ方法计算了它们的二阶非线性光学系数β值。通过对这些化合物性质的分析发现：（１）取代基Ｂｒ不仅能有效地增强微观非线性能能有效地增强材料的宏观非线性效应。（２）取代基Ｂｒ有利于改善材料的透光性能的和热稳定性;（３）分子在晶体中的空间取向是影响材料宏观非线性的另一个重要因素。     

Large Optical Nonlinearity Induced by Singlet Fission in Pentacene Films

By creating two triplet excitons from one photo‐excited singlet exciton, singlet fission in organic semiconductors has drawn tremendous attention for its potential applications in boosting the efficiency of solar conversion. Here, we show that this carrier‐multiplication effect can also be used to dramatically improve the nonlinear optical response in organic materials. We have observed large optical nonlinearity with a magnitude of χ⁽³⁾ up to 10^?9 esu in pentacene films, which is further shown to be a result of singlet fission by monitoring the temporal dynamics. The potential application of such efficient nonlinear optical response has been demonstrated with a singlet‐fission‐induced polarization rotation.     

Influence of Metal Complexing on the Nonlinear-Optical Properties of Compounds with High Molecular Symmetry

Coordination bonding of 1,5-diphenylpentadienone was studied with the aim to prepare compounds exhibiting third-order nonlinear optical properties. The volume resistivity of these compounds was studied as influenced by the third-order nonlinear susceptibility tensor.