Fabrication of UV-curable silicone coating with high transmittance and laser-induced damage threshold for high-power laser system

Journal of Sol-Gel Science and Technology - Third harmonic generating (THG) element is an important component for high-power laser system and its incident side is in need of high transmittance and...     

Formation of nonlinear optical KSm(PO3)4 crystals in phosphate glasses by YAG laser irradiation

Some glasses such as 15K₂O·15Sm₂O₃·70P₂O₅ giving the formation of the nonlinear optical KSm(PO₃)₄ phase through the usual crystallization in an electric furnace and through Nd:YAG laser (1064 nm) irradiation have been developed. The crystallization of the KSm(PO₃)₄ phase showing a second harmonic generation (SHG) is confirmed from X-ray diffraction analysis and micro-Raman scattering spectra. The lines consisting of the KSm(PO₃)₄ phase are constructed by YAG laser irradiation with a power of 0.8 W and a moving speed of 0.5 μm s⁻¹. It is suggested that the crystal growth rate of KSm(PO₃)₄ during laser irradiation is extremely low. The micro-photoluminescence spectra for Sm³⁺ in the crystal lines show the Stark splitting and large intensities compared with the glass part. It is demonstrated that the samarium atom heat processing is effective in the spatially selected crystallization even in phosphate glasses.     

Inorganic supramolecular compounds with 3-D chiral frameworks show potential as both mid-IR second-order nonlinear optical and piezoelectric materials

Two inorganic supramolecular compounds, (Hg(6)P(3))(In(2)Cl(9)) (1) and (Hg(8)As(4))(Bi(3)Cl(13)) (2), which have chiral 3-D host frameworks with guest moieties filling the helical tunnels, have been synthesized. They both have large second-harmonic generation efficiencies, and compound 2 also exhibits obvious single-crystal piezoelectric performance. Theoretical studies from first-principles calculations were performed on their nonlinear optical (NLO) and piezoelectric properties, and results indicate that good NLO and piezoelectric materials can be obtained by designing both complicated polycations and polyanions with large molecular polarizability as functional components rather than traditional single polyanions.     

To improve the key properties of nonlinear optical crystals assembled with tetrahedral functional building units

Nonlinear optical (NLO) crystals assembled with conventional non-π-conjugated tetrahedral functional building units (FBUs), generally referring to [PO₄] and [BO₄], usually exhibit weak nonlinearity and poor birefringence. It is currently proposed that partially substituting oxygen atoms with fluoride atoms in these FBUs could enhance these crucial properties. Hence, we investigated for the first time the NLO-related properties of NH₄BAsO₄F (ABAF), which was constructed from tetrahedral [BO₃F] and [AsO₄] FBUs, and enhancements of these properties were observed in this material, that is large second-harmonic generation (SHG) response (2 × KDP) and improved birefringence (0.03 at 1064 nm). Notably, both SHG coefficient and birefringence of ABAF exceeded those of a great majority of phosphates, sulfates, or boron phosphates and achieved a preferable balance. It is interesting that ABAF shows vast structural similarities to the typical NLO crystals Sr₂Be₂B₂O₇ (SBBO) and KBe₂BO₃F₂ (KBBF), which might be the partial reason why it showed improvement in these vital properties. This work may afford some inspiration for enhancing the key performances of NLO crystals assembled with non-π-conjugated tetrahedra.

We report a new nonlinear optical crystal assembled exclusively with tetrahedral functional building units in which enhanced birefringence (Δn) and second-harmonic generation (d_eff) were observed.     

Synthesis and characterization of second-order nonlinear optical polyurethane with high thermal stability

A second-order nonlinear optical polyurethane was formed with an X-type multi-dimensional charge-transfer (CT) chromophore (DNPIPDHPI) and 3,3^′-dimethoxy-4,4^′-diphenyl diisocyanate. Simultaneous poling and polymerization and in situ second harmonic generation (SHG) measurement technique was carried on to evaluate the thermal stability of the poling induced orientation. The SHG signal of the poled polymer film was not decay below 150 °C and remains 90% of relative d₃₃ value at 200 °C, which is better than the results reported in literature. Comparison of thermal stability indicates that the X-type chromophores possess better property in controlling the decay of the SHG activity than classic chromophores.     

Spectroscopic and optical studies on pure and doped single crystals of sulphate-mixed L-arginine phosphate monohydrate--a nonlinear optical crystal

Single crystals of pure and transition metal ions (Cu(2+) and VO(2+))-doped L-arginine sulpho phosphate monohydrate (sulphate-mixed L-arginine phosphate monohydrate, abbreviated as LASP) have been grown by solvent evaporation of the saturated aqueous solution at room temperature and characterized by single-crystal XRD, FT-IR, UV-Vis-NIR and EPR (single-crystal rotation) spectral studies. Kurtz powder technique shows an enhanced second harmonic generation (SHG) efficiency for LASP and its doped analogues than pure LAP. The EPR studies on LASP:VO(2+) reveal that the in-plane sigma-bonding is moderately covalent and the out-of-plane pi-bonding is highly covalent, which could be attributed to the cause of enhanced powder efficiency.     

Composition investigation of lithium niobate crystals and its influence on the optical damage resistance

Optical methods of investigation of the defect structures and the composition of lithium niobate (LiNbO₃) single crystalsis discussed. The intrinsic defects concentrations in lithium niobate crystals (lithium vacancies (V_Li)⁻ and (Nb_Li)⁴⁺ defects, Nb on Li site in the valence state 4+), as a function of the Li/Nb ratio, are also reported. The optical damage resistance of various lithium niobate samples was investigated as a function of the composition. A remarkable increase in the optical damage resistance was found in MgO-doped almost stoichiometric lithium niobate crystals.     

Crystal growth, thermal and optical studies on a semiorganic nonlinear optical material for blue-green laser generation

The semiorganic nonlinear optical material l-histidine bromide (l-HB) has been synthesized in aqueous solution and characterized by FT-IR, FT-Raman and FT-NMR spectroscopic techniques. The single crystals with dimensions 9mm x 4mm x 3mm were grown by slow evaporation techniques. The grown crystals were subjected to single crystal X-ray diffraction to determine the unit cell dimensions. The thermal stability of the grown crystal was analyzed by thermogravimetric (TG), differential thermal (DT) and differential scanning calorimetric (DSC) analyses. The UV-vis transmittance spectrum shows that it has a good optical transmittance in the entire visible region with the lower cutoff wavelength at 220 nm. The SHG conversion efficiency and laser damage threshold were measured using a Nd:YAG laser (1064 nm). The optical birefringence was measured in the visible region as a function of temperature in the range 30-150 degrees C by interference technique.     

卟啉-多酸复合物材料非线性光学研究进展

随着工业生产、国防科技、医药研究等诸多领域对激光技术日益增长的需求,非线性光学材料逐渐成为人们关注并研究的重点。由于卟啉具有较大的平面化π共轭结构等特性,因此被认为是优异的光学材料。在研究卟啉衍生物的非线性光学(NLO)性质时,为了提高卟啉的NLO性质,研究者们的工作主要集中在官能团的取代和芳环结构的扩展上,但是非线性极化率仍不满足工业化要求,同时卟啉还存在溶解性差等缺点,这些限制了卟啉NLO性质的进一步应用。多金属氧酸盐(多酸,POMs)是由前过渡金属元素与氧原子相互键合形成的一类金属氧簇化合物,有着丰富的电子和结构多样化等特点,是一种优良的电子接受体,多酸能够和卟啉相结合得到一类有较高稳定性和溶解性且具有较大NLO极化率的杂化物。为了能够较为全面地介绍目前卟啉-多酸复合物在非线性光学领域方面的进展,本文基于不同材料结构对非线性光学性能的影响机制进行系统性的综述。本文首先讲述了基于非共价和共价连接方式合成的粉体类卟啉-多酸复合物材料在结构和机理方面的研究进展,然后,介绍了不同的构筑方式对薄膜类卟啉-多酸复合物材料的非线性光学影响,以及薄膜厚度对其在非线性光学性质的影响,最后,本文对该领域未来的发展提出了一些展望。这篇文章旨在为研究卟啉-多金属氧酸盐类物质并增强其非线性光学性质、提高实际应用价值提供研究思路。希望能够给卟啉-多酸复合物材料与非线性光学领域的同行研究者们提供一定的借鉴参考。     

Recent progress in chiral photonic band‐gap liquid crystals for laser applications

This article describes a brief review of recent research advances in chiral liquid crystals (CLCs) for laser applications. The CLC molecules have an intrinsic capability to spontaneously organize supramolecular helical assemblages consisting of liquid crystalline layers through their helical twisting power. Such CLC supramolecular helical structures can be regarded as one‐dimensional photonic crystals (PhCs). Owing to their supramolecular helical structures, the CLCs show negative birefringence along the helical axis. Selective reflection of circularly polarized light is the most unique and important optical property in order to generate internal distributed feedback effect for optically‐excited laser emission. When a fluorescent dye is embedded in the CLC medium, optical excitation gives rise to stimulated laser emission peak(s) at the band edge(s) and/or within the CLC selective reflection. Furthermore, the optically‐excited laser emission peaks can be controlled by external stimuli through the self‐organization of CLC molecules. This review introduces the research background of CLCs carried out on the PhC realm, and highlights intriguing precedents of various CLC materials for laser applications. It would be greatly advantageous to fabricate active CLC laser devices by controlling the supramolecular helical structures. Taking account of the peculiar features, we can envisage that a wide variety of supramolecular helical structures of CLC materials will play leading roles in next‐generation optoelectronic molecular devices. © 2010 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Published online in Wiley InterScience ( www.interscience.wiley.com ) DOI 10.1002/tcr.201000013     

A novel metal-organic network with high thermal stability: nonlinear optical and photoluminescent properties

A novel zinc(II) 4-(5H-tetrazol)benzoic coordination polymer with an in situ generated tetrazole ligand exhibits the gsi (gamma-silicon) topology and high thermal stability; this compound possesses second-order nonlinear optical and interesting heat-induced photoluminescent properties.     

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。     

Investigations on the physicochemical properties of the nonlinear optical crystal for blue green laser generation

Bisglycinehydrogenchloride (BGHC) an intriguing material for frequency conversion has been grown by slow evaporation solution growth technique at room temperature. Their structural, optical and physicochemical properties were characterized by X-ray powder diffraction, FTIR, Raman and UV-vis spectra. The title crystal has found to crystallize into noncentrosymmetric orthorhombic P2(1)2(1)2(1) space group. The material has a wide transparency in the entire visible region. It is found that the cutoff wavelength lies in the UV region. The mechanical response of the crystal has been studied using Vickers microhardness technique. The Kurtz powder second harmonic generation test shows that the compound is a prospective crystalline material for second order nonlinear optical application.     

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。     

Charge-transfer exciton trapping at vacancies in molecular crystals: photoconductivity quenching,optical damage and detonation

Calculations are presented that show that vacancies can trap charge-transfer (CT) states in anthracene, acetanilide and hexahydro-1,3,5-trinintro-1,3,5-triazine (RDX). Such trapping provides a mechanism for photoconductivity quenching by geminate recombination, and for optical damage and detonation by concentrating optical or mechanical energy stored in CT states.     

Structural, thermal and optical characterization of a Schiff base as a new organic material for nonlinear optical crystals and films with reversible noncentrosymmetry

Macroscopic single crystals of (E)-5-(diethylamino)-2-((3,5-dinitrophenylimino)methyl)phenol (DNP) were obtained from slow cooling of chloroform or dichlorometane saturated solutions at controlled temperature. X-ray diffraction analysis showed that this compound crystallizes in a noncentrosymmetric space group (P2(1)2(1)2(1)). Thermal analysis was performed and indicated that the crystals are stable until 260 °C. Second-order nonlinear optical properties of DNP were experimentally investigated in solution through EFISH technique and in solid state through the Kurtz-Perry powder technique. Crystals of compound DNP exhibited a second-harmonic signals 39 times larger than of the technologically useful potassium dihydrogenphosphate (KDP) under excitation at infrared wavelengths. In addition, the second-order nonlinear optical properties of DNP were also studied at visible wavelengths through the photorefractive effect and applied to demonstrate dynamic holographic reconstruction.