Journal articles on the topic 'Inorganic compounds : Nonlinear optics : Second harmonic generation'

The structural and nonlinear optical properties of a new anilinium hybrid crystal of chemical formula (C6H7NCl+·NO3 −)3 have been investigated. The crystal structure was determined from single-crystal X-ray diffraction measurements performed at a temperature of 100 K which show that the compound crystallizes in a noncentrosymmetric space group (Pna21). The structural analysis was coupled with Hirshfeld surface analysis to evaluate the contribution of the different intermolecular interactions to the formation of supramolecular assemblies in the solid state that exhibit nonlinear optical features. This analysis reveals that the studied compound is characterized by a three-dimensional network of hydrogen bonds and the main contributions are provided by the O...H, C...H, H...H and Cl...H interactions, which alone represent ∼85% of the total contributions to the Hirshfeld surfaces. It is noteworthy that the halogen...H contributions are quite comparable with those of the H...H contacts. The nonlinear optical properties were investigated by nonlinear diffuse femtosecond-pulse reflectometry and the obtained results were compared with those of the reference material LiNbO3. The hybrid crystals exhibit notable second (SHG) and third (THG) harmonic generation which confirms its polarity is generated by the different intermolecular interactions. These measurements also highlight that the THG signal of the new anilinium compound normalized to its SHG counterpart is more pronounced than for LiNbO3.

A new nonlinear optical crystals fluoride carbonate, Na4Yb(CO3)3F, has been synthesized by mild hydrothermal method. The Na4Yb(CO3)3F crystallizes in the noncentrosymmetric space group Cc (no. 9) with the lattice parameters a = 8.018(3), b = 15.929(5), c = 13.950(5) Å and β = 101.425(6)°. The compound Na4Yb(CO3)3F has a high density of [CO3] groups. The structure can be described as one-dimensional [Na5Yb(CO3)2F2] chains connected by [CO3] groups, forming an intricate three-dimensional (3D) framework. Other Na+ and Yb3+ cations are located in the cavities of 3D network. The powder second harmonic generation (SHG) measurement shows that Na4Yb(CO3)3F features a large SHG response, about 4.3 times that of KH2PO4 (KDP), and is a phase-matchable material. In addition, its UV-Vis-NIR diffuse reflectance spectral data indicate that Na4Yb(CO3)3F has a large optical gap about 4.72 eV, which corresponds to the UV cut-off edge of 263 nm.

In order to find new ionic compounds with good characteristics for second harmonic generation (SHG), the relationship between first hyperpolarizabilities (β) and the position of the cationic center with respect to the benzene ring was investigated. The β values of a series of trimethylammonium cations: X–C 6 H 4–( CH 2)n N +( CH 3)3, where X = H , CH 3, OCH 3, NH 2, and N ( CH 3)2; n = 0–2, were calculated by using the MOPAC PM3 method. Relatively large calculated β values were obtained when X = N ( CH 3)2 and X = NH 2. Series of [4-(dimethylamino)phenyl]trimethylammonium ( X = N ( CH 3)2; n = 0) and [2-(4-aminophenyl)ethyl]trimethylammonium ( X = NH 2; n = 2) derivatives were synthesized. Among them, seven SHG-active complexes were found and four crystal structures were determined.

AbstractTwo-dimensional (2D) organic-inorganic hybrid perovskites feature characteristics of inherent quantum-well structures and intriguing optoelectronic properties, and have therefore attracted enormous research attention for their optical applications in light emitting, sensing, modulation, and telecommunication devices. The low-cost and solution-processed fabrications as well as alternative organic spacer cations endue 2D hybrid perovskites with higher tunability in optical and photonic applications. In particular, they demonstrate distinguished nonlinear optical characters such as second-harmonic generation (SHG), two-photon absorption (2PA), and saturable absorption (SA) under the excitation of laser pulses. Here, we discuss the construction of the various sorts of 2D hybrid perovskites with different structural features. We have also highlighted some representative properties and applications of these 2D hybrid perovskites in both linear and nonlinear optical regimes.

Boron and tin complexes have been a versatile and very interesting scaffold for the design of nonlinear optical (NLO) chromophores. In this paper we present a wide range of reports since the 1990s to date, which include second-order (e.g., second harmonic generation) and third-order (e.g., two-photon absorption) NLO properties. After a short introduction on the origin of the NLO response in molecules, the different features associated with the introduction of these inorganic motifs in the organic-based NLO materials are discussed: Their effect on the accepting/donating capabilities of the substituents, on the efficiency of the π-conjugated linkage, and on the topology of the chromophores which can be tuned from the first generation of “push-pull” chromophores to more sophisticated two- or three-dimensional architectures.

This paper aims to review the advances achieved in the field of nonlinear optics in relation to phthalocyanines and other related compounds. The main focus is on electronic nonlinear processes, such as second- and third-harmonic generation, and mostly on the work performed by Portuguese and Spanish research groups. Several aspects in which these teams were pioneers are described in more detail. In particular, they performed numerous experiments in solution, thanks to their synthetic efforts in preparing soluble compounds, thus enabling the determination of the nonlinear parameters at a molecular level. They also measured for the first time the real and imaginary components (i.e. the magnitude and the phase) of the nonlinear parameters of phthalocyanines and, in some cases, their frequency dispersion behavior. Such detailed studies allow for the elaboration of microscopic models to identify the electronic levels involved in nonlinear processes. Some Spanish groups were also pioneers in the characterization of the nonlinear optical properties of unsymmetrically substituted phthalocyanines and other related compounds, such as triazolehemiporphyrazines and subphthalocyanines.

Интерес к изучению систем, содержащих сульфиды формулой АIВIIIСVI2, обусловлен, прежде всего, открывающимися возможностями их практического использования в изготовлении нелинейных оптических приборов, детекторов, солнечных батарей, фотодиодов, люминофоров и др. Поэтому в связи с поиском новых перспективных материаловна основе тиогаллата серебра и железа целью этой работы является исследование квазибинарного разреза FeGa2S4–AgGaS2 четырехкомпонентной системы Fe–Ag–Ga–S.Синтез сплавов системы AgGaS2–FeGa2S4 проводили из лигатур с использованием высокой чистоты: железа – 99.995 %, галлия – 99.999 %, серебра – 99.99 % и серы – 99.99 %. Исследование сплавов проводили методами дифференциально-термического, рентгенофазового, микроструктурного анализов, а также измерением микротвердости и определениемплотности.Методами физико-химического анализа впервые изучена и построена Т-x фазовая диаграмма разреза AgGaS2–FeGa2S4, который является внутренним сечением квазитройной системы FeS–Ga2S3–Ag2S. Установлено, что система относится к простому эвтектическому типу. Состав эвтектической точки: 56 мол. % FeGa2S4 и Т = 1100 К. На основе исходных компонентов были определены области твердых растворов. Растворимость на основе FeGa2S4 и AgGaS2 при эвтектической температуре достигает до 10 и 16 мол. % соответственно. С уменьшением температуры твердые растворы сужаются и при комнатной температуре составляют на основе тиогаллата железа (FeGa2S4) 4 мол. % AgGaS2,а на основе тиогаллата серебра (AgGaS2) 11 мол. % FeGa2S4. ЛИТЕРАТУРА 1. Zhаo B., Zhu S., Li Z., Yu F., Zhu X., Gao D. Growth of AgGaS2 single crystal by descending cruciblewith rotation method and observation of properties. Chinese Sci. Bull. 2001; 46(23): 2009–2013. DOI:https://doi.org/10.1007/BF029019182. Горюнова Н. А. Сложные алмазоподобные полупроводники. М.: Сов. радио; 1968. 215 с.3. Абрикосов Н. Х., Шелимова Л. Е. Полупроводниковые материалы на основе соединений АIVBVI..М.:Наука; 1975. 195 с.4. Kushwaha A. 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Linear and nonlinear optical properties of the four isomorphic orthorhombic (point groupmm2) potassium rare earth nitrates K2[RE(NO3)5(H2O)2], with RE = La, Ce, Pr or Nd, have been investigated. Refractive indices in a wavelength range from 0.35 to 2.5 µm and the transmission spectra between 0.25 to 3.0 µm were measured. Using the Maker fringe technique, the d_{ijk}^{\rm\, SHG} coefficients of second-harmonic generation for a fundamental of the Nd–YAP laser (λ = 1079.5 nm) were determined for all four compounds. The d_{ijk}^{\rm\, SHG} coefficients of all four substances are about three times larger than those of KDP, as was first published by Ebberset al.[IEEE J. Quantum Electron.(1993),29, 497–507] for K2[La(NO3)5(H2O)2]. These nitrates are promising materials for application to nonlinear optics (e.g.second-harmonic generation of Nd laser radiation). The nonlinear optical properties of these compounds seem to have their origin mainly in the nitrate groups, as indicated by a simple model (summing the molecular hyperpolarizabilities of the NO3group). Neglecting local field effects, the hyperpolarizability of the NO3group was calculated as β222= 2.52 × 10−40 m4 V−1.

In the context of personalized medicine, there is a growing interest in materials bearing at the same time diagnostic and therapy functions. This article reports a cheap and easily reproducible procedure to obtain materials with a high potential for these applications. Three new strontium iodide–fructose-based metal–organic frameworks with formulae [Sr(C6H12O6)2]I2, [Sr2(C6H12O6)3(H2O)3]I4·0.5H2O and [Sr(C6H12O6)(H2O)3I]I differing in stoichiometry, symmetry and crystal packing, were obtained and characterized by X-ray diffraction. Bulk quantum simulations show that both the ions and the sugar are crucial in determining the predicted nonlinear response; also, the relative arrangement of various functional groups in the unit cell plays a role in the computed optical properties. Small fragments of the three compounds were selected for in vacuo calculations, proving that the reduced dimensions of the particles have a great influence on the nonlinear optical response. Despite the similar chemical composition of the three compounds, second harmonic generation measurements and in crystal and in vacuo theoretical calculations agree that one of the compounds is a much more efficient second harmonic emitter than the other two, and is thus a suitable candidate for bio-sensor applications.

This short review outlines the main results obtained in the field of molecular materials based on zinc coordination compounds for second-order nonlinear optics. It presents an overview of the main classes of second-order nonlinear optical (NLO) active complexes bearing monodentate, bidentate, tridentate, or tetradentate π-delocalized ligands such as substituted stilbazoles, bipyridines, phenanthrolines, terpyridines, and Schiff bases. Macrocyclic ligands such as porphyrins and phthalocyanines are not covered. This paper shows how coordination to the Zn(II) center of π-delocalized nitrogen donor ligands produces a significant enhancement of their quadratic hyperpolarizability. Dipolar complexes are mainly presented, but octupolar zinc complexes are also presented. The coverage is mainly focused on NLO properties that are measured at the molecular level, working in solution, by means of the electric field-induced second harmonic generation (EFISH) or the hyper-Rayleigh scattering (HRS) techniques.

Crystal engineering of novel materials for nonlinear optics (NLO) based on 2-aminopyrimidine yielded two molecular cocrystals with boric acid—trigonal (P3221 space group) 2-aminopyrimidine—boric acid (3/2) and monoclinic (C2/c space group) 2-aminopyrimidine—boric acid (1/2). In addition to crystal structure determination by single crystal X-ray diffraction, the cocrystals were characterized by powder X-ray diffraction and vibrational spectroscopy (FTIR and FT Raman). Large single crystals of the non-centrosymmetric cocrystal 2-aminopyrimidine—boric acid (3/2) were grown to study the optical properties and determine the second harmonic generation (SHG) efficiency (using 800 nm fundamental laser line) of powder samples.

A nonlinear optical (NLO) microscope has been developed based on recording the second harmonic generation (SHG) signals of the B 2- and B 4-phases of bent shaped liquid crystalline (LC) materials. We observed that the microstructures of the polar order can be accurately characterized by 2D scanned images implementing this device. Specifically, we have investigated two bent-core compounds, which have either B 4 or B 2 phases at room temperature and exhibit SHG activity. The NLO microscope was calibrated according to the Maker-fringes method allowing the in situ evaluation of the relative SHG efficiency. The developed NLO microscopy device may serve as an important tool to characterize liquid crystalline features at a microscopic scale for both fundamental and applied research.

In the last few decades optical imaging techniques based on nonlinear optical properties have been of interest for biosensing applications. This work focuses on two isostructural and isomorphous sugar-derived metal–organic frameworks (MOFs) with second-harmonic generation (SHG) properties, in order to investigate their possible application as biosensors in view of their high biocompatibility. Combining 2-deoxy-D-galactose with the metal halogenides CaX 2 (X = Br, I), two new isomorphous MOFs of formula [Ca(C6H12O5)2]X 2 were obtained and characterized through single-crystal X-ray diffraction. The first-order static hyperpolarizability and second-order susceptibility were estimated by in vacuo and in-crystal density functional theory calculations, and compared with the experimental SHG response of powdered samples. The parameters influencing the SHG response of these compounds were investigated by comparison with similar previously analysed MOFs, to understand how to design more efficient materials to be used as nanoprobes by exploiting crystal engineering techniques.

A nonlinear optical (NLO) microscope has been developed based on recording the second harmonic generation (SHG) signals of the B 2- and B 4-phases of bent-shaped liquid crystalline (LC) materials. We observed that the microstructures of the polar order can be accurately characterized by 2D scanned images implementing this device. Specifically, we have investigated two bent-core compounds, which have either B 4 or B 2 phases at room temperature and exhibit SHG activity. The NLO microscope was calibrated according to the Maker fringe method allowing the in situ evaluation of the relative SHG efficiency. The developed NLO-microscopy device may serve as an important tool to characterize liquid crystalline features at a microscopic scale for both, fundamental and applied research.

ABSTRACTThe properties for members of a new class of nonlinear optical (NLO) materials which stoichiometrically incorporate organic and inorganic constituents into a single crystalline lattice are reported. Recent results for our synthetic, crystal growth, and optical studies suggest that a number of these relatively transparent “semiorganic” compounds have significant second and/or third order NLO responses and often display favorable crystal growth morphologies.The prototype material of this class, zinc tris(thiourea) sulfate, or ZTS, has a UV cutoff at about 325 nm, can be readily grown to cm3 sizes, and has been shown to be a highly efficient Type II frequency doubler for 1064 nm Nd:YAG laser radiation. ZTS also possesses a moderate third order nonlinear optical response (ca. 0.1 × CS2) which occurs on at least a picosecond time scale as determined by degenerate four-wave mixing (DFWM) experiments at 532 nm.Refractive index, second harmonic generation, and DFWM data for a number of these new compounds are presented.

ABSTRACTThe phenomenon of second harmonic generation has been studied from the earliest days of nonlinear optics.[l] To date the most impressive results in terms of conversion efficiency for as low an input power as possible have been obtained in channel waveguides made from inorganic materials.[2] However, when their second order nonlinearities (10s of pm/V) are compared with those of organic materials (10s → 100s pmn/V), it is clear that organic materials should eventually produce much better harmonic conversion efficiencies. [3]

The present report lists selected publications on centrosymmetric compounds that manifest second harmonic generation responses in a laser, along with a few publications that dispute the laser outcomes. Two studies provide a plausible explanation for this apparent contradiction between second-order nonlinear susceptibility and inversion symmetry: the crystals are noncentrosymmetric and are twinned by inversion. If crystal structures of SHG-active compounds are presented in centrosymmetric settings, the authors of the publications may consider stipulating that the true space group is likely to be one of the noncentrosymmetric sub-space groups.

Doped glassy polymers have been examined as potential materials for nonlinear optical (NLO) device applications[l-Il1]. In these systems, dopants with excellent nonlinear optical capabilities are dispersed in glassy polymer matrices with good physical properties to make versatile and efficient NLO materials[1-4]. The optical technique of second harmonic generation (SHG), conversion of light of frequency to to light of frequency 2o, is performed as a function of time to examine the temporal stability of NLO dopant orientation in the polymer matrix[I-4]. Through the use of poling, the NLO dopants are aligned into the noncentrosymmetric orientation required for SHG to occur[1-4,7]. Polymeric NLO materials have a number of advantages over the current commercial inorganic crystals, including ease of fabrication and processability, low laser damage, low cost, and excellent chemical and physical resistance[8-10]. Due to the relaxation behavior characterizing glassy polymers even at temperatures well below the glass transition temperature Tg, the dopants can disorient as a function of time following poling[1-4,12,13]. This results in a loss of optical performance with time. The purpose of this work is to examine the basic polymer physics that govern the temporal stability of the dopant orientation and disorientation and related optical behavior as a function of the local microenvironment surrounding the NLO dopants. Systems studied include bisphenol-A-polycarbonate (PC), polystyrene (PS) and poly(methyl methacrylate) (PMMA) doped with well characterized NLO dyes such as 4-dimethylamino-4′- nitrostilbene (DANS) and 4-amino-4′-nitroazobenzene (or disperse orange 3, D03).