High Nonlinear Optical Activity Research Articles

Phenyl-urea chromophores: DFT insights into nonlinear optical enhancement

The present investigation has examined the nonlinear optical (NLO) responses of molecules based on phenyl-urea. The optimized geometries of complexes: (4-nitrophenyl) urea (PU1), 1-methyl-3-(4-nitrophenyl) urea (PU2), and 1,1-dimethyl-3-(4-nitrophenyl) urea (PU3) are extracted using M06–2X/6–311++ g (d, p) level of theory. The estimated nonlinear optical responses (NLO) of the compounds given are based on static and dynamic hyperpolarizabilities, which are reinforced by the dipole moment, polarizabilities, global reactivity parameters, HOMO-LUMO gap, molecular electrostatic potentials (MEP), and βvec. Comparing PU1, PU2, and PU3 to reference substances like urea and p-nitroaniline, a considerably higher NLO activity is estimated. Out of all the compounds, PU3 has the largest NLO response. Such a significant NLO reaction can be attributed to a small HOMO-LUMO gap and high charge transfer. Second-harmonic generation (SHG) and electro-optic Pockel's effect (EOPE) are being explored for dynamic NLO responses. These compounds that are bases of phenyl-urea exhibit a very significant quadratic nonlinear optical response.

Metal modulated effects on the optoelectronic and charge transport properties of some graphene nanoribbons

In this study, we have investigated the effects of adding a metal on the nonlinear, mechanical and charge transport properties of some small organic graphene nanoribons (GNRs) molecule. A theoretical investigation is done using the ab initio (rhf) and DFT (B3LYP and BPBE) methods with the 6-31+g(d,p) basis set integrated in Gaussian 09. Results reveals that the metalated GNRs have higher nonlinear optical activity than the virgin counterpart. Interestingly these GNRs metal derivatives also have remarkable nonlinear optical effect in comparison to the classical push–pull organic crystal; para-nitroaniline and urea. Other remarkable results show that as compared to the starting GNRs the metalated counterparts are excellent ambipolar charge transport carriers better than the prototypic electron transport Alq3 (tris(8-hydroxyquinolinato)aluminum(III), and hole tranport TPD (N,N0-diphenyl-N,N0-bis(3-methlphenyl)-(1,10-biphenyl)-4,40-diamine. However, the metal derivative have diminished mechanical stability than the starting molecule. Metalated GNRs could therefore serve as potential candidates for the fabrication of optoelectronic and photonic devices for second and third-order NLO application.

Ca6.5Pb1.5ZnBi(VO4)7, a novel whitlockite-type vanadate: crystal structure refinement and properties characterization

Novel compounds Ca8−xPbxZnBi(VO4)7(0 ≤x≤ 1.5) solid solution with the whitlockite-type structure were synthesized by a standard solid-state method. The unit-cell parameters were determined by X-ray powder diffraction and using Le Bail decomposition. The crystal structural of Ca6.5Pb1.5ZnBi(VO4)7was refined by Rietveld method. It is found that Pb2+cations occupy a half of theM3 site, whereas theM1 andM2 sites are predominantly occupied by calcium with admixture of Bi3+cations. TheM5 site is fully occupied by Zn2+cations. TheM4 site in the structure of studied sample remains vacant and does not participate in the cations arrangement. Optical second harmonic generation demonstrates high non-linear optical activity. Dielectric investigations confirm polar space groupR3c. Changes in the non-linear optical and ferroelectric parameters are matched with lead and zinc cation distribution over the sites of the whitlockite-type structure.

Structure-Property Relationships in Click-Derived Donor-Triazole-Acceptor Materials.

To shed light on intramolecular charge-transfer phenomena in 1,2,3-triazole-linked materials, a series of 1,2,3-triazole-linked push-pull chromophores were prepared and studied experimentally and computationally. Investigated modifications include variation of donor and/or acceptor strength and linker moiety as well as regioisomers. Photophysical characterization of intramolecular charge-transfer features revealed ambipolar behavior of the triazole linker, depending on the substitution position. Furthermore, non-centrosymmetric materials were subjected to second-harmonic generation measurements, which revealed the high nonlinear optical activity of this class of materials.

Spectroscopic and theoretical study of the charge transfer interaction effect on the vibrational modes and nonlinear optical properties in l-asparaginium nitrate crystal

Single crystals of l-asparaginium nitrate (LAsnN) were grown by slow evaporation technique. To confirm the crystalline nature of the obtained compound, samples were the subject of an XRPD. The density functional theory (DFT) computations were carried out at B3LYP/6-31G (d) level to reach the optimized geometry, the vibrational spectra and the NLO properties. The excellent agreement between simulated and observed vibrational spectra led to a reliable vibrational assignment. To demonstrate the various charge transfer interactions that stabilize the compound and led to the high nonlinear optical activity, NBO analysis was performed. Also, owing to the hydrogen bond formation, a lowering in the HOMO-LUMO energy gap is noticed. Moreover, as a result of the charge transfer interactions, the symmetry of the nitrate ions was lost and some forbidden modes were excited.

Growth mechanism, electronic spectral investigation and molecular orbital studies of l-prolinium phosphate

By using atomic force microscopy, birth and spread has proved to be the primary growth mechanism for l-prolinium phosphate (LPP). The phenomenon of newly formed islands expanding to the edge of the preceding terrace was observed. The optimized molecular structure and the molecular properties were calculated by density functional theory method. Natural bond orbital analysis was carried out to demonstrate the various inter and intramolecular interactions that are responsible for the stabilization of LPP leading to high NLO activity. Molecular electrostatic potential, frontier molecular orbital analysis and thermodynamic properties were investigated to get a better insight of the molecular properties. Global and local reactivity descriptors were computed to predict the reactivity and reactive sites on the molecules. Non-linear optical (NLO) properties such as the total dipole moment (μ) and first order hyperopolarizability (β) were also calculated to predict NLO behavior.

Deep-ultraviolet transparent phosphates RbBa2(PO3)5 and Rb2Ba3(P2O7)2 show nonlinear optical activity from condensation of [PO4](3-) units.

It is challenging to explore deep-ultraviolet (deep-UV) nonlinear optical (NLO) materials that can achieve a subtle balance between deep-UV transparency and high NLO activity. Known deep-UV NLO materials are almost exclusively limited to borates, except few newly discovered phosphates despite their small NLO activities. Here we report two asymmetric phosphates, RbBa2(PO3)5 (I) and Rb2Ba3(P2O7)2 (II), which feature [PO3]∞ chains and [P2O7](4-) dimers formed by condensation of [PO4](3-) units, respectively. Remarkably, I achieves the desired balance, with the shortest deep-UV absorption edge at 163 nm and the largest NLO activity of 1.4 × KDP (KH2PO4) in deep-UV NLO phosphates. According to first-principles calculations, the enhanced macroscopic SHG response of I can be attributed to the [PO3]∞ chains which exhibit significantly larger microscopic SHG coefficients as compared with the [P2O7](4-) dimers.

Density functional theory studies on molecular structure and vibrational spectra of NLO crystal l-phenylalanine phenylalanium nitrate for THz application

Molecular structure, FT-IR and Raman spectra of l-phenylalanine phenylalanium nitrate have been investigated using density functional theory calculation. The polarizability and hyperpolarizability value of the crystal is also calculated. Natural bond orbital analysis confirms the presence of intramolecular charge transfer and the hydrogen bonding interaction. Simultaneous activation of ring CC stretching modes shows the non-centrosymmetric symmetry. Terahertz time-domain spectroscopy has been used to detect the absorption spectra in the frequency range from 0.05 to 1.3 THz. Theoretically predicted β value exhibits the high nonlinear optical activity.

Vibrational spectra and structural studies of nonlinear optical crystal ammonium D, L‐tartrate: a density functional theoretical approach

AbstractSingle crystals of ammonium D, L‐tartrate, a potential nonlinear optical (NLO) material of interest, were grown by the slow evaporation technique. The crystal structure was determined by single‐crystal X‐ray diffraction. Fourier transform infrared and Raman spectra of the crystallized molecule were recorded and analyzed. The geometry, intermolecular hydrogen bonding, first hyperpolarizability and harmonic vibrational wavenumbers were calculated with the help of B3LYP density functional theory method. The red shift of hydroxyl and NH4+ stretching wavenumbers indicate the formation of inter‐ and intramolecular hydrogen bonding. Simultaneous activation of CH stretching wavenumbers shows the presence of intramolecular charge transfer in the molecule. Natural bond orbital analysis was carried out to demonstrate the various inter‐ and intramolecular interactions that are responsible for the stabilization of this molecule, leading to high NLO activity. Copyright © 2010 John Wiley & Sons, Ltd.

Synthesis and Properties of Novel Y-type Nonlinear Optical Polyester Containing Cyanovinylthiophene with Enhanced Thermal Stability of Second Harmonic Generation

The organic materials seem to be superior because of their high er nonlinear optical activity and faster response time than the inorganic ones. Among the organic materials, NLO polymers are receiving great attention, mainly because they offer many advantages such as mech-anical endurance, light weight , chemical resistance, and good processability to form electro-optic devices. A potential NLO polymer must contain highly polarizable conjugated dipolar electronic systems and they have to be mechanically very strong and thermally stable with high glass-transition tem-perature (

Crystal structure of the lead bromo-borate Pb2[B5O9]Br from precision single-crystal X-ray diffraction data and the problem of optical nonlinearity of hilgardites

The structural features responsible for the high nonlinear optical activity of crystals of the hilgardite-like anhydrous bromo-borate Pb2[B5O9]Br (space group Pnn2) are analyzed with the use of data obtained from two (precision and conventional) single-crystal X-ray diffraction experiments. The electron-density peaks associated with the stereochemically active lone electron pair are located in free space at two equally probable positions in the vicinity of the Pb(2) atom on the side of the two most distant atoms, Br(1) and Br(2). The stereochemical activity of two nonequivalent lead atoms in the crystal structure increases upon changing over from the Pb(1) atom to the Pb(2) atom. This is in agreement with the behavior of the lone electron pairs in the hilgardite-like hydrated borate Na0.5Pb2[B5O9](OH)1.5 · 0.5H2O and another nonlinear optical borate, namely, Pb2[B4O5(OH)4](OH)2 · H2O, which is related to the compound BiB3O6. The most pronounced nonlinear optical properties of the lead bromo-borate Pb2[B5O9]Br as compared to other orthorhombic hilgardites and lead borates are associated with the presence of highly polarized Pb-Br bonds. In this case, the electron density of the lone electron pair of the Pb(2) atom enhances the polarization effect.

Potassium bromo-borate K3[B6O10]Br—A new nonlinear optical material

A new polar hexaborate, K{sub 3}[B{sub 6}O{sub 10}]Br (space group R3m), is synthesized under hydrothermal conditions. The radical anion is composed of macallisterite hexaborate blocks 6[3{delta} + 3T] formed by boron triangles and boron tetrahedra. The blocks are joined together through vertices into a [B{sub 6}O{sub 10}]{sub {infinity}}{sub {infinity}}{sub {infinity}}{sup 2-} zeolite-like framework of a new type. Large K{sup +} cations and Br{sup -} anions are located in extended channels that are aligned parallel to rhombohedral translations of the crystal lattice. The structure of the sublattice formed by large ions consists of BrK{sub 6} bromo-centered octahedra, which are linked together through vertices into a hexagonally distorted perovskite framework. The perovskite framework is inserted into the boron-oxygen framework so that these two frameworks do not intersect. The nonlinear optical properties of powdered samples of the K{sub 3}[B{sub 6}O{sub 10}]Br compound are investigated using the second harmonic generation method. It is found that the K{sub 3}[B{sub 6}O{sub 10}]Br compound exhibits a high nonlinear optical activity that exceeds the activities of the majority of borate compounds and is characteristic of haloid borates of the hilgardite family.

Nonlinear‐Optical Susceptibility of Hilgardite‐Like Borates M2B5O9X (M: Pb, Ca, Sr, Ba; X: Cl, Br).

AbstractFor Abstract see ChemInform Abstract in Full Text.

Nonlinear-optical susceptibility of hilgardite-like borates [formula omitted][formula omitted]; [formula omitted

Usage of non-centrosymmetric boron oxide derivative crystals as nonlinear elements may be a key solution of pressing problem of obtaining powerful radiation at shorter wavelengths via frequency multiplication of solid state laser radiations. It is shown that Pb 2B 5O 9Br and some other members of hilgardite-like borohalogenides demonstrate in powder form, high non-linear optical activity in the SHG experiments. An attempt is made using the Philips–Van Vechten–Levine–Xue bond theory to calculate second-order nonlinear coefficients for isostructural to mineral hilhardite noncentrosymmetric crystals M 2 B 5 O 9 X with M = Pb , Sr, Ba, Eu, Ca and X = Cl , Br. Theoretically obtained values of nonlinear optical coefficients d i j k only partly correlate with the results of SHG measurements. In particular, the experiments distinctively show sharp increase of nonlinear activity along the series Ca < Sr < Ba < Pb and Cl < Br of metal boro-halogenides, while theoretical estimations give substantially more slack composition dependences. Analysis of contribution of different boron–oxygen bonds to optical nonlinearities of the compounds reveals important role of planar BO 3 triangles, though this factor is yet unable to explain enormously high SHG output from Pb 2B 5O 9Br.

Investigations of nonlinear optical (NLO) properties of Fe, Ru and Os organometallic complexes using high accuracy density functional theory (DFT) calculations

Organometallic and coordination complexes are interesting candidates for NLO purposes. Among these materials bimetallic complexes belong to a new class of second order NLO materials. The objective of this investigation was to design a range of novel bimetallic molecular systems, which show high nonlinear optical activity. In this investigation, main attention was drawn to the ferrocenyl systems coupled with group eight metal carbonyls, where charge transfer occurs from ferrocene to the metal carbonyl moiety. These novel ferrocene bimetallic systems show high first static hyperpolarizability values. We report novel organometallic systems with high β values. The high accuracy density functional theory (DFT) was used for the investigation of NLO properties of these complexes. The full geometry optimisations of designed bimetallic systems were performed using DFT method at B3LYP/LanL2DZ level of theory using the gaussian98W. The calculations of the first static hyperpolarizabilities of these systems were performed at the same level of theory.

Synthesis of photoconducting nonlinear optical side-chain polymers containing carbazole derivatives

Two kinds of multifunctional monomers, 2-methyl-acrylic acid 6-[3-[2-cyano-2-(4-nitrophenyl)-vinyl]-carbazol-9-yl]hexyl ester (M1) and 2-methyl-acrylic acid 6-[3-[2-(4-nitrophenyl)-vinyl]-carbazol-9-yl]hexyl ester (M2) were synthesized to possess both photoconductivity and nonlinear optical (NLO) properties. Photoconducting NLO polymers (P1, P2) were obtained by the copolymerization of these multifunctional monomers with methylmethacrylate. Charge-transporting monomer, 2-methyl-acrylic acid 6-[3-(diphenyl-hydrazonomethyl)-carbazol-9-yl]hexyl ester (M3) was also synthesized and copolymerized with M1 or M2 to give the photoconducting NLO polymers (P3, P4) with enhanced photoconductivity. The successful polymerization was identified by spectroscopic means and gel permeation chromatography analysis. These polymers were very soluble in common solvents and high optical quality films could be easily fabricated by spin coating. Second harmonic generation (SHG) measurement confirmed P1 and P2 possessed high NLO activity. From the preliminary measurement of photoconductivity, it was found that P1 possessed distinct photoconductivity. It was also found that P3 and P4 showed much higher photoconductivity than P1, presumably due to the enhanced charge transporting property of M3 structure.

Synthesis and second-order nonlinear optical characteristics of linear and crosslinked epoxy polymers

4-Nitro-4′-amino-biphenyl (p-NBA), a photo- and thermostable chromophore with high nonlinear optical (NLO) activity, was used to react with various epoxy resins, then three linear functionalized epoxy polymers were obtained and further crosslinked with a trimer of hexamethylene diisocynate during poling process. The second harmonic generation behaviors of linear and crosslinked poled polymers have been investigated. The crosslinked epoxy polymer based on bisphenyl-A with p-NBA moieties exhibits high NLO activity and stability

Nonlinear optical polymers in advanced photonics

AbstractDevelopment of advanced photonic devices requires extensive integration of several technologies. Electrooptical devices must simultaneously satisfy several materials properties including: high nonlinear optical activity, thermal stability, mechanical strength, and optical transparency. In addition, the device materials must be amenable to fabrication, and must be compatible in a multi‐layered configuration. We have recently developed polymers which meet these complex requirements. Indeed, electrooptical devices have been demonstrated using these polymers. This paper is a comprehensive review of the development of such devices, from design of the molecular architecture to waveguide design and fabrication. The critical issues in each aspect of device development are discussed. © 1994 John Wiley &amp; Sons, Inc.