Academic literature 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. K., Khenata R., Bouhemadou A., Bin-Omran S., Haddadi K. Lattice dynamical propertiesand elastic constants of the ternary chalcopyrite compounds CuAlS2, CuGaS2, CuInS2, and AgGaS2. Journalof Electronic Materials. 2017;46(7): 4109–4118. DOI: https://doi.org/10.1007/s11664-017-5290-65. Uematsu T., Doi T., Torimoto T., Kuwabata S. Preparation of luminescent AgInS2-AgGaS2 solid solutionnanoparticles and their optical properties. The Journal of Physical Chemistry Letters. 2010;1(22):3283–3287. DOI: https://doi.org/10.1021/jz101295w6. Karaagac H., Parlak M. The investigation of structural, electrical, and optical properties of thermalevaporated AgGaS2 thin films. J. Thin Solid Films. 2011;519(7): 2055–2061. DOI: https://doi.org/10.1016/j.tsf.2010.10.0277. Karunagaran N., Ramasamy P. Synthesis, growth and physical properties of silver gallium sulfi de singlecrystals. Materials Science in Semiconductor Processing. 2016;41: 54–58. DOI: https://doi.org/10.1016/j.mssp.2015.08.0128. Zhou H., Xiong L., Chen L., Wu L. Dislocations that decrease size mismatch within the lattice leadingto ultrawide band gap, large second-order susceptibility, and high nonlinear optical performance of AgGaS2.Angewandte Chemie International Edition. 2019;58(29): 9979–9983. DOI: https://doi.org/10.1002/anie.2019039769. Li G., Chu Y., Zhou Z. From AgGaS2 to Li2ZnSiS4: Realizing impressive high laser damage thresholdtogether with large second-harmonic generation response. Journal Chemistry of Materials. 2018;30(3):602–606. DOI: https://doi.org/10.1021/acs.chemmater.7b0535010. Yang J., Fan Q., Yu Y., Zhang W. Pressure effect of the vibrational and thermodynamic properties ofchalcopyrite-type compound AgGaS2: A fi rst-principles investigation. Journal Materials. 2018;11(12): 2370.DOI: https://doi.org/10.3390/ma1112237011. Paderick S., Kessler M., Hurlburt T. J., Hughes S. M. Synthesis and characterization of AgGaS2nanoparticles: a study of growth and fl uorescence. 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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 Thesis is concerned with the prediction, synthesis, characterization and testing of inorganic materials for Second Harmonic Generation (SHG). Chapter One describes the fundamentals of non-linear optics, and poses the problems, and some of their solutions which confront the synthetic chemist and the theoretical prediction of the second order hyperpolarizability constant β using CNDOVSB calculations. Chapter Two describes the design, implementation and calibration of an apparatus for measurements of the second harmonic generating efficiency of solids based on the Kurtz powder technique, and a solvatochromic method for the determination of β. Novel compounds with potential chirality due to atropisomerism, asymmetric octahedral structures, and asymmetric tetrahedral symmetry of metal centers are discussed in Chapters Three to Five. Chapter Three surveys the use of pentane-2,4-dionato- ligands and their coordination compounds as possible NLO active materials. The single crystal X-ray structures of bis(triphenylphosphine)(4-nitrobenzoylacetonato)palladium(II) tetrafluoroborate and tris(triphenylphosphine)[3-(2,4-dinitrophenyl)-pentane-2,4-dionato]palladium(II) tetrafluoroborate were determined. Chapter Four describes the syntheses, characterization and SHG properties of trans-β-ionylidenecyanoacetic acid (2-cyano-3-methyl-5-(2,6,6-trimethyl-l-cyclohexen-1- yl)-2,4-pentadienoic acid) and some of its metal and non-metal salts. Chapter Five describes the synthesis, characterization and second harmonic generation properties of some platinum(II) and palladium(II) complexes of β- ionylidenecyanoacetic acid. Chapter Six describes the use of conventional asymmetric carbon centers to introduce chirality into centrosymmetric compounds. The chiral compound (L)-N-[2-cyano- 3-methyl-5-(2,6,6-trimethyl-1 -cyclohexene-1 -yl)-2,4-pentadiene-1 -one]-L-proline and some of its salts were synthesized from β-ionylidenecyanoaeetic acid and tested for SHG.

Detailed studies are presented of thin films containing a polycation, a nonlinear optically (NLO) active chromophore, and a synthetic hectorite that self-assemble into the noncentrosymmetric structure required for second order nonlinear optical responses. UV/Vis spectroscopy and ellipsometry were used as probes to monitor film growth for upto 25 deposition cycles. Exceptionally homogeneous films were obtained with regular film growth for up to the 25 cycles deposited. ISAM films self-assemble from polyelectrolyte solutions due to coulombic interactions between a charged substrate and the charged polymer in solution. Charges accumulating at the surface restrict further growth due to charge overcompensation at the surface. The entire process occurs relatively quickly as compared to other competing assembly techniques such as Langmuir-Blodgett assembly and covalent self-assembly. Previous studies indicated that second harmonic signal diminishes after the deposition of the first few bilayers. This is potentially due to adjacent layer interpenetration, which becomes prominent moving further away from the hard substrate interface. Laponite RD, a synthetic hectorite was introduced in the films in an effort to minimize interpenetration of adjacent bilayers and hence maintain chromophore orientation in every bilayer of the ISAM film. The film was deposited in quadlayers that have the following sequence: Polycationâ Laponiteâ Polycationâ Chromophore. This study is unique in its approach as it investigates the possible implications of film interpenetration on the NLO-activity of ISAM films that can be easily fabricated. It also shows the effects of different interfaces on the NLO-activities of the films. We have investigated the effect of changing the polycation from poly(allylamine hydrochloride) (PAH) and poly(diallyldimethylammonium chloride) (PDDA) and the solution pH to see how these variables affect the growth and NLO properties of ISAM films. At lower pH values (specify relevant range of values), for both polycations, intrachain and interchain repulsion is strong due to little electrostatic screening. This results in polycation deposition in relatively thin, train-like layers. At higher pH levels (specify relevant range of values here) the electrostatic screening is greater due to a higher effective ionic strength. At these conditions, intrachain and interchain repulsion is reduced and so the polymers adsorb to form thicker layers with more loops and tails than for the case at lower pH. This also results in a higher density of the chromophore in the film. Extremely smooth surfaces of Laponite RD in film were obtained as confirmed by AFM imaging on glass. Regular quadlayer growth monitored by UV/Vis spectroscopy and ellipsometry was observed for up to 25 quadlayers. Second harmonic generation (SHG) signal was not conclusively affected by the presence of laponite as the decrease of signal was seen after the first few layers in the laponite containing films. This decrease was however was not as sharp in the films containing laponite as in the films that did not contain laponite. It was also noted that the SHG was not so much affected by the number of layers deposited but more so by the distance of the chromophore layer from the hard glass interface. This study thus brings to light the very important effect of the glass interface on the NLO-activity of these films.
Master of Science

Nous avons déterminé l'hyper polarisabilité de premier ordre, de nouvelles molécules organiques : des molécules organométalliques chirales, des systèmes photochromes et des molécules a transfert de charge bidimensionnel (molécules en). Nous avons tout d'abord réalisé le montage de génération de second harmonique induite par un champ électrique (efishg) afin de mesurer en solution la projection sur le moment dipolaire permanent de l'hyper polarisabilité vectorielle a 1,064 m et a 1,907 m. L'analyse de l'amplitude et de la valeur moyenne du signal de second harmonique permet de tenir compte de l'absorption du second harmonique généré lorsque celle-ci n'est pas négligeable. Ces résultats expérimentaux ont été compares a ceux obtenus par des calculs semi-empiriques, bases sur la méthode <<<>am1<>>>, combines a la méthode <<<>champ fini<>>>. Après optimisation de la géométrie, nous avons déterminé les différents termes du tenseur d'hyper polarisabilité à fréquence nulle des molécules dans le vide. Nous nous sommes intéressés a des dérivés du ferrocène possédant une forte hyper polarisabilité. Différentes substitutions ont permis de rendre ces composes chiraux tout en conservant leurs propriétés moléculaires non-linéaires. En raison de la chiralité, la maille cristalline de ces molécules ne possède donc pas de centre d'inversion. Nous avons ensuite étudié des composes de deux familles de photochromes, les fulgides et les diaryléthènes. L'absence de retour thermique de la forme colorée vers la forme de départ et la bonne résistance à la photo dégradation rendent ces molécules intéressantes pour le stockage de l'information. Nous avons recherche des isomères photochimiques ayant des hyper polarisabilités moléculaires différentes et un taux de conversion photo induit réversible important. Les molécules en l possèdent deux axes de transfert de charge. Le terme prépondérant dans le tenseur d'hyper polarisabilité n'est pas le terme diagonal. En modélisant les molécules en l par deux ressorts non-linéaires couples, nous avons obtenu des relations entre les différents termes de ce tenseur et démontre le couplage entre les deux ressorts. Nous avons également mis en évidence que la structure moléculaire en favorise un assemblage cristallin sans centre d'inversion.

In recent years, coinage metal nanoparticles have emerged as materials with largest quadratic optical nonlinearity. Their first hyperpolarizabilities (β) are very high (105-106 x 10-30 esu) but such large values were quite unexpected because of their apparently centrosymmetric bulk structure. Only a small second harmonic generation (SHG) from coinage metal nanoparticles is expected through higher order multipolar (e.g., quadrupolar) polarization mechanisms. Various possible reasons have been attributed to the observation of large β values in coinage metal nanoparticles. They are: 1) Particles may not be overall centrosymmetric (as appears from the TEM pictures) which, in turn, can make SHG electric dipole allowed, 2) Several polarization mechanisms (dipolar, quadrupolar, retardation, etc.) may be operating simultaneously to render SHG very efficient, 3) SHG can be resonance enhanced if the incident or SH photons fall within the surface plasmon resonance (SPR) absorption bands or higher energy interband transitions in the metal particles, and 4) Surface capping agents used for stabilization of the nanoparticles in solution alter the SH response. It is, therefore, important to experimentally find out which of the above mentioned possibilities are dominant and under what conditions we can identify the contribution of various mechanisms to the overall SHG response of the coinage metal nanoparticles. In this thesis work, the origin of SHG from copper (one of the coinage metals) nanoparticles has been investigated using hyper-Rayleigh scattering (HRS). In chapter 1, an introduction to metal nanoparticles and their optical properties have been presented. A general introduction to second order nonlinear optics and various methods for the determination of first hyperpolarizability are provided. A literature survey on the second order NLO properties of metal nanoparticles is also done. At the end of the chapter, the motivation of the work done is outlined. In chapter 2, the experimental set-ups for unpolarized and polarization resolved hyper-Rayleigh scattering (HRS) measurements at different wavelengths are described. Generation of IR wavelength of 1543 and 1907 nm using stimulated Raman scattering in gases have been presented in this chapter. In chapter 3, synthesis and characterization of copper nanoparticles are described. Four different size copper nanoparticles (5, 9, 25, and 55 nm) were prepared by laser ablation. Size dependencies of first hyperpolarizability were investigated at different wavelengths and it was found that β increases with increasing size of the particle and that the SHG originates mainly from the surface of the particle. Dispersion in first hyperpolarizabilities of the copper nanoparticles has also been investigated and we find that at incident and SH wavelengths far from the SPR absorption band, the hyperpolarizability is large compared to molecular hyperpolarizabilities. In chapter 4, the results of polarization resolved HRS measurements on copper nanoparticles of five different sizes at four different wavelengths (738, 1064, 1543 and 1907 nm) are reported. Polarization analyses show that at small particle size to wavelength (d/λ) ratio the dipolar contribution to SHG is dominant whereas the quadrupolar and retardation effects become important at larger d/λ values. The “small particle limit” in the SHG from coinage metal nanoparticles has been assessed based on our results on copper and others’ results on silver and gold nanoparticles. In chapter 5, the effect of surface capping on the first hyperpolarizability of copper nanoparticles is investigated. Polyvinyl pyrrolidone (PVP) has been used as a capping agent. The results obtained for bare and capped copper nanoparticles show that capping enhances the hyperpolarizability by a factor of 2. In the last chapter 6, general conclusions drawn on SHG from coinage metal nanoparticles based on this work are presented along with future perspectives.