Deep-Ultraviolet Transparent Mixed Metal Sulfamates with Enhanced Nonlinear Optical Properties and Birefringence

Enhancing anisotropy through the controlled arrangement of anionic groups is essential for improving the nonlinear optical (NLO) performance of non-π-conjugated NLO materials. In this study, we present the successful synthesis of the first examples of mixed alkali metal-alkaline earth metal sulfamate materials, including noncentrosymmetric Cs₂Mg(NH₂SO₃)₄ ⋅ 4H₂O ( 1 ), as well as centrosymmetric K₂Ca(NH₂SO₃)₄ ( 2 ) and Rb₂Ca(NH₂SO₃)₄ ( 3 ). All three compounds feature promising deep ultraviolet cut-off edges, notably 1 with a cut-off edge below 180 nm. The synergy of Cs⁺ and Mg²⁺ cations in 1 facilitated the successful alignment of polar [NH₂SO₃] tetrahedra in a uniform orientation. Remarkably, 1 stands as the sole instance among reported sulfamate compounds with a co-parallel anionic arrangement, yielding a very large dipole moment compared to other non-π-conjugated NLO materials. Moreover, the substantial dipole moment of 1 yields an enhanced second harmonic generation response, approximately 2.3 times that of KH₂PO₄, and a large birefringence of 0.054 at 546.1 nm. The approach of regulating the arrangement of anionic groups using aliovalent cations holds promise for advancing the exploration of non-π-conjugated NLO materials.     

硅酸镓镧族非线性光学晶体

中红外非线性光学晶体可以实现中红外激光频率转换、拓展激光波长,在民用和军用领域中有至关重要的应用价值。其中,硅酸镓镧族晶体具有透过范围宽、激光损伤阈值高、晶体质量好等优势,引起了国内外同行的广泛关注。在这篇综述中,我们基于现有的实验数据,研究和分析了三种重要的硅酸镓镧族晶体La_3Ga_5Si O_(14)(LGS)、La_3Ga_(5.5)Nb_(0.5)O_(14)(LGN)、La_3Ga_(5.5)Ta_(0.5)O_(14)(LGT)的综合性能,详细总结了它们在电光调Q开关和中红外光参量振荡以及差频激光输出方面的应用。最后,本文还讨论了今后硅酸镓镧族中红外非线性光学晶体的重点发展方向。     

有机金属酞菁类化合物及其非线性光限幅特性

随着激光技术的快速发展, 激光武器的性能也越来越优越, 所造成的危害也越来越大, 各国开始加大力度对激光防护材料进行研究. 酞菁化合物具有限幅窗口宽、限幅效果明显、响应迅速等特点, 是一类非常具有应用前景的光限幅材料. 当前, 制备出限幅性能好、稳定性强的酞菁光限幅材料成为激光防护材料领域中的研究热点. 本文评述和总结了近几年在酞菁光限幅材料方面开展的系统研究工作, 首先介绍了酞菁化合物实现光限幅效应的机制, 并在此基础上详细分析了影响光限幅效应的因素以及光限幅器件化过程对酞菁光物理和光限幅性能的影响机理. 根据分析结果提出了在基础和应用研究方面存在的科学问题, 指出了该类型光限幅材料面临的挑战和今后的重要发展方向.     

Mg(C3O4H2)(H2O)2: A New Ultraviolet Nonlinear Optical Material Derived from KBe2BO3F2 with High Performance and Excellent Water-Resistance

Acquiring high-performance ultraviolet (UV) nonlinear optical (NLO) materials that simultaneously exhibit a strong second harmonic generation (SHG) coefficients, as short as possible SHG phase-matching (PM) wavelength and non-hygroscopic properties has consistently posed a significant challenge. Herein, through multicomponent modification of KBe₂BO₃F₂ (KBBF), an excellent UV NLO crystal, Mg(C₃O₄H₂)(H₂O)₂, was successfully synthesized in malonic system. This material possesses a unique 2D NLO-favorable electroneutral [Mg(C₃O₄H₂)₃(H₂O)₂]_∞ layer, resulting in the rare coexistence of a strong SHG response of 3×KDP (@1064 nm) and short PM wavelength of 200 nm. More importantly, it exhibits exceptional water resistance, which is rare among ionic organic NLO crystals. Theoretical calculations revealed that its excellent water-resistant may be originated from its small available cavity volumes, which is similar to the famous LiB₃O₅ (LBO). Therefore, excellent NLO properties and stability against air and moisture indicate it should be a promising UV NLO crystal.     

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.     

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.     

An n-Type Polythiophene Derivative with Excellent Thermoelectric Performance

Typical n-type conjugated polymers are based on fused-ring electron-accepting building blocks. Herein, we report a non-fused-ring strategy to design n-type conjugated polymers, i.e. introducing electron-withdrawing imide or cyano groups to each thiophene unit of a non-fused-ring polythiophene backbone. The resulting polymer, n-PT1 , shows low LUMO/HOMO energy levels of −3.91 eV/−6.22 eV, high electron mobility of 0.39 cm² V⁻¹ s⁻¹ and high crystallinity in thin film. After n-doping, n-PT1 exhibits excellent thermoelectric performance with an electrical conductivity of 61.2 S cm⁻¹ and a power factor (PF) of 141.7 μW m⁻¹ K⁻². This PF is the highest value reported so far for n-type conjugated polymers and this is the first time for polythiophene derivatives to be used in n-type organic thermoelectrics. The excellent thermoelectric performance of n-PT1 is due to its superior tolerance to doping. This work indicates that polythiophene derivatives without fused rings are low-cost and high-performance n-type conjugated polymers.     

Inorganic Solid-State Nonlinear Optical Switch with a Linearly Tunable Tc Spanning a Wide Temperature Range

Nonlinear optical (NLO) switch materials that turn on/off second-harmonic generation (SHG) at a phase transition temperature (T_c) are promising for applications in the fields of photoswitching and optical computing. However, precise control of T_c remains challenging, mainly because a linearly tunable T_c has not been reported to date. Herein, we report a unique selenate, tetragonal P 2₁c [Ag(NH₃)₂]₂SeO₄ with a=b=8.5569(2) Å and c=6.5208(2) Å that exhibits a strong SHG intensity (1.3×KDP) and a large birefringence (Δn_obv.=0.08). This compound forms a series of isostructural solid-solution crystals [Ag(NH₃)₂]₂S_xSe_1−xO₄ (x=0–1.00) that exhibit excellent NLO switching performance and an unprecedented linearly tunable spanning 430 to 356 K. The breaking of localized hydrogen bonds between SeO₄²⁻ and the cation triggers a phase transition accompanied by hydrogen bond length changes with increasing x and a linear change in the enthalpy .     

Multi-Stimuli Responsive Luminescence and Domino Phase Transition of Hybrid Copper Halides with Nonlinear Optical Switching Behavior

Although phase transition materials (PTMs) under external stimuli are of great research interest duo to their rich potential applications, it is still challenging to explore multi-responsive PTMs. Herein, two different phases of organic–inorganic hybrid copper-based halides, α- and β-Gua₃Cu₂I₅ (Gua⁺=CN₃H₆⁺), were synthesized by solvent evaporation method, which they crystalize in the noncentrosymmetric space group Fdd2 with zero-dimensional structure and centrosymmetric space group C2/c with one-dimensional metal-halogen framework, respectively. Interestingly, it is firstly demonstrated that Gua₃Cu₂I₅ simultaneously possesses reversible PL conversion and NLO switching properties in response to thermal stimulus. Strikingly, apart from heat, its structural phase transition can also be triggered by crystalline-phase-recognition (CPR) and mechanical force. These new findings may pave a path for future exploration of PTMs with multiple physical properties.     

Spectroscopic Properties and Three-photon Absorption Induced Optical Limiting of Series of Novel Nonlinear Chromophores

Three novel nonlinear chromophores with symmetric D-π-D molecular structure and extended conjugated length were synthesized. Solvatochromism analysis shows great symmetric intramolecular charge transfer occurring in chromophores by the enhancement in the dipole moment between the ground and excited states. The properties of optical power limiting induced by three-photon absorption (3PA) are demonstrated. Large 3PA coefficients and the corresponding molecular cross sections as high as 10-74 cm6s2 were obtained for nanosecond laser pulses at 1.06 μm from nonlinear transmission measurements.     

Synthesis,Structure, and Properties of Nonlinear Optical Crystal Na2SiF6

Nonlinear optical crystals of fluosilicate Na₂SiF₆ are synthesized via hydrothermal method and its structure is determined by single‐crystal X‐ray diffraction (XRD). The space group of Na₂SiF₆ is P321 with cell parameters a = 8.8715(3) Å, c = 5.0484(5) Å, Z = 3, V = 344.09(4) ų. The properties of the crystal are measured by powder XRD, infrared (IR) spectroscopy, ultraviolet/visible (UV/Vis) near‐infrared (NIR) diffuse reflectance spectroscopy, thermogravimetric (TG), and differential scanning calorimetry (DSC) analysis. The bandgap calculated using CASTEP is 7.41 eV, indicating that the cut‐off edge of the Na₂SiF₆ crystal can be down to deep‐UV energy region. The first‐principles studies were performed to elucidate the structure/property relationship of Na₂SiF₆.     

不同形态银纳米粒子的非线性光学特性

通过光诱导生长制备了三角形和圆盘形银纳米粒子, 并采用飞秒Z-scan技术考察了这2种形貌的银纳米粒子在800 nm光波长下的非线性光学特性. 在基态等离子漂白和自由载流子吸收等效应的作用下, 粒径为75 nm的三角形银纳米粒子的非线性透过率随激发光强的增加而呈现由饱和向反饱和非线性吸收过渡的现象; 粒径为35 nm的圆盘形银纳米粒子仅表现出反饱和吸收现象. 实验结果表明, 银纳米粒子非线性吸收过程受粒子形态调控.     

Unbiased Screening of Novel Infrared Nonlinear Optical Materials with High Thermal Conductivity: Long-neglected Nitrides and Popular Chalcogenides

Traditional infrared (IR) nonlinear optical (NLO) materials such as AgGaS₂ are crucial to key devices for solid-state lasers, however, low laser damage thresholds intrinsically hinder their practical application. Here, a robust strategy is proposed for unbiased high-throughput screening of more than 140 000 materials to explore novel IR NLO materials with high thermal conductivity and wide band gap which are crucial to intrinsic laser damage threshold. Via our strategy, 106 compounds with desired band gaps, NLO coefficients and thermal conductivity are screened out, including 8 nitrides, 68 chalcogenides, in which Sr₂SnS₄ is synthesized to verify the reliability of our process. Remarkably, thermal conductivity of nitrides is much higher than that of chalcogenides, e.g., 5×AgGaS₂ (5.13 W/m K) for ZrZnN₂, indicating that nitrides could be a long-neglected system for IR NLO materials. This strategy provides a powerful tool for searching NLO compounds with high thermal conductivity.     

Bioapplications Manipulated by AIEgens with Nonlinear Optical Effect

The modern medicine requires precise diagnostic techniques while the fluorescent imaging shows great potential in such applications due to its excellent sensitivity and high resolution.However,conducting fluorescent imaging in deep-tissue is not so easy because most luminogens show short-wavelength excitation,which may undergo severe light scattering by the bio-tissue.The marriage of fluorescent imaging with nonlinear optical(NLO)effect can alleviate such adverse effects by utilizing NIR laser to reduce light scattering.On the other hand,scientists are enthusiastic in pursuing luminescent materials,which can match well with NLO application.Aggregation-induced emission(AIE)materials exhibit huge advantages in such aspect not only because of its high luminescent efficiency in aggregate state but also due to its excellent photo-stability(a key factor to meet laser application because of its ultrahigh energy density).Inspired by this,many interesting and meaningful works have sprung up based on AIE luminogens with NLO effect in recent years,and for such reason,it motivates us to summarize them to give a systematic presentation.Here,we first give a brief introduction of the principle of NLO effect.Secondly,the strategies for improving the NLO effect of AIE materials,such as increasing molecular conjugation,introduction of donor-acceptor effect,induction of centrally asymmetric array of AIE molecules in crystals and introduction of intermolecular interactions are clarified.In the final part,we also present the multiple applications of AIEgens with NLO effect in cell imaging,deep-tissue tumor and brain blood vessel imaging and photodynamic therapy.We believe,with this review,the topic will attract more attention from the scientists in multi-science field to accelerate the development of AIE materials in biomedical applications.     

Synthesis,Crystal Structure and Nonlinear Optical Properties of a new cluster compound: MoS4Cu3(PyPPh2)3Cl

Reaction of [NH₄]₂[MoS₄], CuCl and PyPPh₂ in the solid state produces a cube-like cluster. The cluster crystallizes in the orthorhombic space group P2₁2₁2₁ with four formula units in a cell of dimensions a = 12.8980(10) , b = 17.6820(10), c = 22.665(2) Å. Anisotropic refinement for all nonhydrogen atoms yielded the values R = 0.0397 and R _w = 0.1185 for 8803 observed reflections. The structure is built up from three [Cu(Ph₂PPy)]⁺ units bridged by MoS^2? ₄ to form a tetranuclear symmetrical cube-like molecule. Investigation of the third-order optical nonlinear value showed that it exhibits a considerable nonlinear absorptive and self-defocusing effect with α₂ = 1.3 × 10^?11 m w^?1 and n ₂ = ? 3.2 × 10^?18 m² w^?1 in a 1.5 × 10^?4 M DMF solution.     

新型合偶氮功能团的双炔类衍生物非线性光学性质的理论研究

在SM1和ZINDO方法基础上，按完全态求和公式计算分子二阶非线性光学系数β(ijk)和三阶非线性光学系数γ(ijkl)，并对含偶氛功能团的双快类衍生物的二阶、三阶非线性光学性质进行了系统的理论研究．即在基础上，在分子左端引入推电子基N（CH3）2，右端分别引入推电子基CH2OH、2，5-二氮-4-硫甲苯基，研究取代基变化时β、γ变化的规律．对计算结果所反映的规律性在微观上给予了解释．     

关于二阶非线性光学性质的分子设计研究

在INDO/CI基础上,用完全态求和公式自编程序计算二阶非线性光学系数β_ijk,考察了分子骨架、受电子基团或给电子基团变化对β_x的影响,并设计了最大β_x的化合物、计算结果均与实验值相符。     

Design of the Ionic Organic Nonlinear Optical Material NH4[LiC3H(CH3)O4] with Ultrawide Band Gap and Moderate Birefringence

Ionic organic crystals containing organic planar π-conjugated units has become one of the hot spots as nonlinear optical (NLO) materials. However, although this type of ionic organic NLO crystals commonly have remarkable second harmonic generation (SHG) responses, they also suffer from overlarge birefringences and relatively small band gaps that be hardly beyond 6.2 eV. Herein, a flexible π-conjugated [C₃H(CH₃)O₄]²⁻ unit was theoretically revealed, showing great potential for designing NLO crystals with balanced optical properties. Accordingly, through the reasonable NLO-favourable layered design, a new ionic organic material, NH₄[LiC₃H(CH₃)O₄], was successfully obtained. As expected, it achieves not only a large SHG effect (4×KDP), but also a suitable birefringence (0.06@546 nm) and an ultrawide band gap (>6.5 eV). This study provides a new flexible π-conjugated NLO-active unit, contributing to design more ionic organic NLO materials with excellent balanced optical properties.     

高Tg交联型二阶非线性光学聚合物的合成

合成了双羟基双氨基偶氮苯化合物，将其分别与六亚甲基二异氰酸酯的缩二脲和２，４－甲苯二异氰酸酯进行交联反应合成了两种交联型二阶非线性光学聚合物，利用ＦＴＩＲ光谱和ＤＳＣ对交反应过程和交联聚合物的玻璃化转变温度进行研究。采用ＵＶ－Ｖｉｓ吸收光谱对极化交联反应前后膜的取向及取向稳定性进行了研究。     

Cs3In(In4Se7)(P2Se6): A Multi-Chromophore Chalcogenide with Excellent Nonlinear Optical Property Designed by Group Grafting

Non-centrosymmetric (NCS) and polar materials capable of exhibiting many important functional properties are indispensable for electro-optical technologies, yet their rational structural design remains a significant challenge. Here, we report a “group grafting” strategy for designing the first multi-chromophore selenophosphate, Cs₃In(In₄Se₇)(P₂Se₆), that crystallizes in a NCS and polar space group of Cm. The structure features a unique basic building unit (BBU) [In(In₄Se₁₀)(P₂Se₆)], formed through “grafting [In₄Se₁₀] supertetrahedra on the root of [In(P₂Se₆)₂] groups”. Theoretical calculations confirm that this [In(In₄Se₁₀)(P₂Se₆)] BBU can achieve a “1+1>2” combination of properties from two chromophores, [In₄Se₁₀] supertetrahedron and ethane-like [P₂Se₆] dimer. That makes Cs₃In(In₄Se₇)(P₂Se₆) exhibit excellent linear and nonlinear optical (NLO) properties, including a strong second harmonic generation (SHG) response (~6×AgGaS₂), a large band gap (2.45 eV), broad infrared (IR) transmission (up to 19.5 μm), a significant birefringence (0.26 @1064 nm) as well as the congruently-melting property at ~700 °C. Therefore, Cs₃In(In₄Se₇)(P₂Se₆) will be a promising NLO crystal, especially in the IR region, and this research also demonstrates that “group grafting” will be an effective strategy for constructing novel polar BBUs with multi-chromophore to design NCS structures and high-performance IR NLO materials.