A novel class of nonlinear optical materials based on host-guest composites: zeolites as inorganic crystalline hosts

The demand for nonlinear optical (NLO) materials with exceptional NLO properties is very large, and hence the search for such materials should be continued not only to enhance their functions in current applications but also to help expedite the materialization of photonics in which photons instead of electrons are used for signal processing, transmission, and storage. This article summarizes the preparation, characteristics, and the future perspectives of novel second order nonlinear optical (2NLO) materials prepared by orientation-controlled incorporation of 2NLO molecules into zeolite channels and third order nonlinear optical (3NLO) materials prepared by compartmentalization of very small (<1.3 nm) PbS QDs within zeolite nanopores under different environments, and the novel chemistry newly unveiled during the preparation of novel zeolite based NLO materials.     

Metal oxyhalides: an emerging family of nonlinear optical materials

Second-order nonlinear optical (NLO) materials have drawn enormous academic and technological attention attributable to their indispensable role in laser frequency conversion and other greatly facilitated applications. The exploration of new NLO materials with high performances thus has long been an intriguing research field for chemists and material scientists. However, an ideal NLO material should simultaneously satisfy quite a few fundamental yet rigorous criteria including a noncentrosymmetric structure, large NLO coefficients, desired transparent range, large birefringence, high laser damage threshold, and availability of a large-size single crystal. Therefore, the identification of promising compound systems, targeted design, and experience-based syntheses are crucial to discover novel NLO materials working in the spectral region of interest. As an important family of mixed-anion compounds, versatile metal oxyhalides containing metal-centered oxyhalide functional units ([MO_mX_n] (X = F, Cl, Br, and I)) are becoming a marvelous branch for interesting NLO materials. Especially, when the central metals are d⁰/d¹⁰ transition metals or heavy post-transition metals, a number of novel NLO materials with superior functionalities are expected. Our thorough review on the recent achievements of metal oxyhalides for NLO materials are divided into the fast-growing NLO metal oxyhalides with single type halogen anions and the newly identified NLO metal oxyhalides with mixed halogen anions. Here we mainly focus on the design strategy, structural chemistry, NLO-related properties, and structure–property correlation of the metal oxyhalides with relatively large NLO responses. We hope this review can provide an insight on the rational design and future development of emerging metal oxyhalides for NLO and other applications.

Nonlinear optical metal oxyhalides could provide a new insight into the target design and exploratory synthesis of new functional materials with intriguing chemical and physical properties.     

Solvent induced enhancement of nonlinear optical response of graphdiyne

Flat and crystalline materials with exceptional nonlinear optical(NLO) properties are highly desirable for their potential applications in integrated NLO photonic devices.Graphdiyne(GD),a new twodimensional(2 D) carbon allotrope,has recently evoked burgeoning research attention by virtue of its tunable bandgap along with a high carrier mobility and extended π-conjugation compared with most conventional optical materials.Here,we experimentally probe the third-order nonlinear optical response of GD dispersed in several common solvents(alcohols) using a femtosecond Z-scan technique.The measured nonlinear optical refractive index is in the order of ~10^-8 cm²/W,which is approximately one order of magnitude higher than that of most 2 D materials.In particular,we find that different NLO responses can be observed from GD when dispersed in different solvents,with the strongest NLO response when dispersed in 1-propanol.It is proposed that some intrinsic properties of the solvents,such as the polarity and viscosity,could influence the NLO response of GD materials.Our experimental results confirm the assumptions on the NLO behavior in GD and demonstrate its great potential for future generations of Kerr-effect-based NLO materials and devices.     

Efficient Nonlinear Optical Properties of Dyes Confined in Interlayer Nanospaces of Clay Minerals

Nonlinear optical (NLO) responses from organic dyes can be maximized when the dyes are aligned in appropriate manners in bulk materials. The use of restricted nanospaces provided by interlayer spacing of inorganic layered materials is a promising strategy for imposing suitable molecular alignments for NLO materials on dyes. The hybrid materials thus obtained exhibit salient NLO responses owing to the improved molecular orientation. In some cases, extension of the π‐electron system as a consequence of improved molecular planarity, obtained by the intercalation of a dye into the 2‐dimensional interlayer space of an inorganic layered material, is also observed as a factor that enhances NLO responses of chromophores at the molecular level. This review focuses on recent progress in the strategies for controlling the molecular orientation of NLO‐phores by employing clay minerals, which are one of the typical inorganic layered materials. In addition, development of a means for fabricating composites that satisfy the properties of an optical material, such as a sufficient size and thickness, a flat surface, and low light‐scattering characteristics is required to utilize the superior NLO properties observed for clay/dye hybrid materials for practical applications. A novel means for obtaining such a hybrid material is also outlined.     

Covalent Organic Frameworks as Emerging Nonlinear Optical Materials

The vastness of organic synthetic strategies and knowledge of reticular chemistry have made covalent organic frameworks (COFs) one of the most chemically and structurally diverse class of materials with potential applications ranging from gas storage, molecular separation, and catalysis to energy storage and magnetism. Recently, this class of porous materials has garnered increasing interest as potential nonlinear optical (NLO) materials. Traditionally, inorganic crystals, small-molecule organic chromophores, and oligomers have been studied for their NLO response. Nevertheless, COFs offer significant advantages over existing NLO materials in terms of higher mechanical strength, thermochemical stability, and extended conjugation. Herein, we discuss crucial aspects, terminology, and measurement techniques related to NLO, followed by a critical analysis of the design principles for COFs with NLO response. Furthermore, we touch on selected potential applications of these NLO materials. Finally, future prospects and challenges of COFs as NLO materials are discussed.     

Synthesis and Study of Second-order Nonlinear Optical Properties of 3-Substituted-6- (substituted-phenylazo) coumarins

It has attracted a lot of attentions to synthesize and investigate the behaviors of organic second-order nonlinear optical (NLO) materials. [1,2] We have ever reported that acridine derivatives ,[3] 4-substituted-benzylideneoxazol-5(4H)-one[4] and 4,4′-di-styryl-biphenyl derivatives[5] possess good second-order NLO properties. Coumarin derivatives are good organic optical materials and azobenzene derivatives possess a higher second-order nonlinear polarization values, however, there are few reports about the study on the synthetic method, optical behavior, especially,second-order NLO properties of 3-substitued-6-(substituted-phenylazo) coumarin derivatives. Therefore, a series of the following compounds were prepared in order to investigate their NLO behavior.     

Recent Progresses of UV Nonlinear Optical Materials

Ultraviolet(UV) nonlinear optical(NLO) crystal materials are hailed as the "chip" of the optoelectronic industry for they play a unique and crucial role in many newly developed scientific and technological applications. At present, due to the relatively single frequency doubling gene types of traditional NLO materials, the service performance of UV NLO materials is fundamentally restricted. Therefore, there is an urgent need to develop new synthesis methods, search for novel functional groups, expand new UV NLO materials systems, screen new high-performance crystals, and then break through performance bottlenecks. Herein, we review the recent progresses on UV NLO crystal materials. Furthermore, we prospect that these recently developed approaches will continuously extend their advantages in developing superior UV NLO materials in the near future.     

Complex coordinated functional groups: A great genes for nonlinear optical materials

Complex coordinated functional groups [MA_xB_y]（M = Central coordination element; A, B = P, O, S, Se,F, Cl, Br or I） are composed of different types of anions A, B jointly linked to the same central cation M,which are in high potential to tune the physical properties of materials, e.g., second-order susceptibility,energy gaps and birefringence. Recently, Compound containing complex coordinated functional groups have attracted great attention in the nonlinear optical（NLO） fiel...     

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.     

Strong optical nonlinearities of self-assembled polymorphic microstructures of phenylethynyl functionalized fluorenones

The polymorphs of a phenylethynyl functionalized fluorenone derivative, and their controlled self-assembly for microstructures with different morphologies have been studied. These polymorphic microcrystals exhibit very distinctive NLO properties, which are highly correlated to their electronic and supramolecular structures.     

Organometallic materials for nonlinear optics

Almost three decades ago, the field of nonlinear optics evolved with the discovery of lasers. In the beginning, nonlinear optical (NLO) phenomena were investigated in inorganic materials, leading to the development of traditional NLO materials such as lithium niobate, potassium titanyl phosphate, quartz and gallium arsenide. In the 1970s, the importance of organic materials was realized because of the promise of large NLO responses, high laser damage thresholds, fast optical responses, architectural flexibility and ease of fabrication. Following work with organic materials, the scrutiny of organometallics also began recently. In organometallics, the metal-ligand bonding is expected to display large molecular hyperpolarizability because of the transfer of electron density between the metal atom and the conjugated ligand system. In organometallics, the diversity of central metals, oxidation states and ligands fosters in optimization of the charge-transfer interactions. Keeping this in view, second- and third-order NLO properties of organometallics have been reviewed here, highlighting new materials that are emerging. Organometallics may have a wide range of applications in opto-electronics including integrated optics, optical switching, telecommunications, bistability and modulation.     

Polymers for Electro‐Optical Modulation

Second‐order nonlinear optical (NLO) properties of polymeric materials have been attracting a lot of attention, especially for such potential applications as fast waveguides electrooptic (EO) modulation and frequency‐doubling devices. For these photonic applications, the performance of the NLO materials has to be optimized. This requires not only a fundamental knowledge of inter‐relationship between their chemical and NLO properties, but new technologies competitive or superior to existing ones as well. This review focuses on the synthesis of NLO polymers including chromophore design, and the comparison among comprehensive EO polymer systems. Moreover, characterization and device fabrication of electro‐optical polymer planar waveguides are also reported in this review.     

Synthesis and Non-linear Optical（NLO） Properties of a Series of Alkoxysilane Derivative Chromophores

1 Introduction Nonlinear optical materials(NLO) have drawn a great intrest of some scholars and scientists in the last dacades because of their tremendous     

金属有机骨架薄膜材料的三阶非线性光学性能研究进展

金属有机骨架(MOFs)材料因其可设计的结构以及灵活可控的配位模式,在三阶非线性光学(NLO)领域引起了广泛的关注。与液体分散状态相比,MOFs在固体状态下的三阶NLO性能更为重要,这不仅可以深入了解MOFs本身所固有的光学性能,还有助于实现MOFs在光学器件中的实际应用。然而,由于散射的存在和透光率的限制,单独的MOFs材料难以直接实现固体状态下的三阶NLO性能研究,将MOFs制备成具有较好光学透过性的薄膜是研究其NLO性能最为可行的一种策略。MOFs薄膜不仅很好地继承了MOFs所固有的三阶NLO性能,而且还结合了薄膜的高透光率以及灵活的机械性能。基于此,本文分析总结了MOFs薄膜的制备方法及其NLO性能研究方面的相关工作,并根据目前MOFs薄膜在三阶NLO性能方面的研究现状对其未来发展予以了展望。     

金属有机骨架薄膜材料的三阶非线性光学性能研究进展

金属有机骨架(MOFs)材料因其可设计的结构以及灵活可控的配位模式,在三阶非线性光学(NLO)领域引起了广泛的关注。与液体分散状态相比,MOFs在固体状态下的三阶NLO性能更为重要,这不仅可以深入了解MOFs本身所固有的光学性能,还有助于实现MOFs在光学器件中的实际应用。然而,由于散射的存在和透光率的限制,单独的MOFs材料难以直接实现固体状态下的三阶NLO性能研究,将MOFs制备成具有较好光学透过性的薄膜是研究其NLO性能最为可行的一种策略。MOFs薄膜不仅很好地继承了MOFs所固有的三阶NLO性能,而且还结合了薄膜的高透光率以及灵活的机械性能。基于此,本文分析总结了MOFs薄膜的制备方法及其NLO性能研究方面的相关工作,并根据目前MOFs薄膜在三阶NLO性能方面的研究现状对其未来发展予以了展望。     

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.     

两种含偶氮苯共轭桥新型生色团分子的合成及性能

通过重氮化偶合反应和羟醛缩合反应合成了以偶氮苯为共轭桥、以2,2,3-三甲基-4-氰基-5-二氰基亚甲基-2,5-二氢呋喃为电子受体, 而给体分别为二甲氨基和二乙氨基的两种有机非线性光学生色团分子MFNC和EFNC. 利用IR、1H NMR和元素分析对分子的结构进行了表征. TGA和DSC测试发现, MFNC的热稳定性略好于EFNC, 其热分解温度最高达266 ℃. 通过测定两种材料在氯仿、丙酮和DMSO中的紫外-可见光谱, 用溶致变色法计算得到两种材料在激光波长为1064 nm处的二阶非线性品质系数μgβ, 对比发现EFNC的μgβ值高于MFNC, 其值达59706×10-48 esu(1 esu=3.34×10-10C).     

聚酰亚胺多层膜的制备及其在非线性光学中的应用

报道了一种通过旋涂制备NLO聚合物多层膜的方法.紫外-可见吸收光谱及膜的厚度表征说明,在所得多层膜的结构中,聚合物单层膜的厚度可以较好地控制在100~200nm之间,所得含有5个双层的NLO多层膜(厚度1.6μm)具有良好的结构均一性,光学显微镜下没有观察到明显的结构缺陷.与单层具有较大厚度的NLO聚合物薄膜(如2~4μm)相比,所得聚合物多层膜可以允许掺杂更多的发色团而不发生相分离.     

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 %     

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.