Second-order Nonlinear Optical Susceptibility Research Articles

Second-harmonic generation studies of differences in molecular orientation of Langmuir–Blodgett films fabricated by vertical and horizontal dipping techniques

Second-harmonic generation (SHG) studies have been carried out on Langmuir–Blodgett films of 2-docosyl-amino-5-nitropyridine that were transferred by two different dipping techniques: vertical y-type and horizontal x-type depositions. The SHG behavior of horizontally transferred films is remarkably different from that of the vertically transferred films. In y-type films the SHG is due mainly to the in-plane component χyyy(2) (which is along the dipping axis) of the second-order nonlinear optical susceptibility tensor and χxxx(2) is negligible. In the case of x-type films, the SHG is due to the in-plane χ(2) tensor components but χyyy(2) and χxxx(2) have comparable magnitudes. In both films the nonlinear optical chromophores lie almost flat with respect to the plane of the substrate. The cancellation of χxxx(2) in y-type films is due to the preferential orientation of molecular domains along the dipping axis. In horizontally transferred films, molecular domains seem to be randomly distributed on the surface.

Dramatically enhanced second-order nonlinear optical susceptibilities in tricyanovinylthiophene derivatives

Experimentally measured second-order nonlinear hyperpolarizability (βµ) data for a new series of donor-acceptor conjugated compounds containing tricyanovinyl acceptors and thiophene conjugating units, reveal that this combination results in a dramatic enhancement (αµ= 6000–9000 × 10–48 esu) of their molecular nonlinearity.

Preparation and characterization of a novel Langmuir-Blodgett film optical waveguide with non-linear optical susceptibility inversion

We demonstrate that a novel Langmuir-Blodgett (LB) film structure with a second-order non-linear optical susceptibility inversion structure in the thickness direction (NIST) can be prepared by the substrate inversion method in which the substrate is turned upside down during the film deposition process. In an NIST structure, the sign of the non-linear optical susceptibility is designed to be inverted at the position where the electric field of the second harmonic wave has a node in the thickness direction of the LB film optical waveguide. A 2-docosylamino-5-nitropyridine LB film is used for the preparation of an NIST structure. From an investigation of the structure using the Maker fringe method, polarized UV absorption spectroscopy and X-ray diffraction, it was indicated that the LB film with an NIST structure was a highly ordered Y-type LB film (bilayer spacing, 4.45 nm) and that the difference from the usual Y-type structure was that the non-linear optical susceptibility was inverted at a designed position in the thickness direction. The interference pattern of the absorption spectrum indicates that the optical scattering due to disorder in the film was weak enough to allow good transparency in the thickness direction. Coherent green second harmonic generation light was observed both from the NIST structure and from the normal structure optical waveguides. The measured Cerenkov angle was about 5° for both of the waveguides. This suggests that the homogeneity in the thickness direction of the linear optical constants of the optical waveguide with the NIST structure is in fair agreement with that with the normal structure.

Second-order nonlinear optical effects in novel side-chain liquid crystalline polymers and monomers under bias of an applied dc electric field

Second-order nonlinear optical susceptibilities of a series of newly synthesized liquid crystalline polymers and corresponding monomers were measured by using second-harmonic generation. A substituted stilbene moiety was selected as the main conjugated π-electronic structure, and systematic modifications were made at the site of the donor and in the conjugation path to compare the roles of various donors and charge-transferring linkages in the second-harmonic-generation process. The β values extracted from the measurements made on solutions and on thin films yielded similar values for the monomers and the corresponding polymers. The variations in β values are discussed in terms of molecular structural properties, charge-transferring power of the donors, and dispersion effect.

A Two-Legged Spacer Molecule for Alternate Layer LB Film Deposition with Optically Nonlinear Dyes

ABSTRACTSecond harmonic generation from Langmuir-Blodgett films of E-N-octadecyl-4-(2-(4-dimethylaminophenyl)ethenyl)pyridinium iodide (a hemicyanine) interleaved with 4, 4'-dioctadecyl-3, 5, 3', 5'-tetramethyldipyrrylmethene hydrobromide (spacer) increases quadratically with the number of active layers, the second-order nonlinear optical susceptibility of film structures comprising from 1 to 150 bilayers being 70 pm/V. The synthesis and nonlinear optical properties are reported.

Relaxation phenomena in polymer nonlinear optical materials

The isothermal decay of the second-order nonlinear optical susceptibility of a guest-host azo dye methacrylate film was measured by second-harmonic generation at a series of temperatures. The decay curves were fit to Williams–Watt–Kohlrausch stretched exponentials. The activation energies and pre-exponential factors were found to agree with those derived from nonisothermal electric-field-induced second-harmonic generation measurements on similar films. It is concluded that a common underlying process involving a distribution of local relaxations governs the film behavior.

Second-Harmonic Generation in Langmuir-Blodgett Monolayer of a Two-Dimensional Charge-Transfer Molecule: N,N′-Dioctadecyl-4,6-Dinitro-1,3-Diaminobenzene

A new amphiphilic dye, N,N′-dioctadecyl-4,6-dinitro-1,3-diaminobenzene (DIODD), which is capable of forming Langmuir-Blodgett (LB) films, has been synthesized and represents a model for a two-dimensional charge transfer (2-D CT) molecule. The stable Langmuir-Blodgett monolayers of a 1:1 mixture of dye and arachidic acid were deposited onto a glass substrate. The Langmuir-Blodgett monolayers exhibited a well-defined fringing pattern resulting from second-harmonic generation. These experimental results have been analyzed in connection with theoretical calculations for the model compounds. Our theoretical calculations demonstrate the superiority of two-dimensional charge transfer molecules over one-dimensional charge transfer molecules in the case in which the LB molecules incline from the normal to the substrate. The molecular orientation of the DIODD molecule is close to the optimum orientation applicable for maximizing χ111(2). Second-order nonlinear optical susceptibilities χ111(2) and χ133(2) determined by analyzing the data were 2.2×10-8 and 7.7×10-9 esu, respectively at a tilt angle of 60°. This work presents the first example of a two-dimensional charge transfer molecule displaying second-harmonic generation from a Langmuir-Blodgett monolayer.

Growth of metanitroaniline film crystal with controlled orientation for optical waveguide second-harmonic generation

The use of organic molecular crystals with large second-order nonlinear optical susceptibilities for implementing compact waveguide second-harmonic generation devices is addressed. The growth of metanitroaniline film crystal in a planar capillary with a channel/taper structure for single seed formation by zone melting recrystallization using a ridge heater is presented. Single-crystal film (5*15 mm/sup 2/, approximately 2- mu m thickness) was obtained with reproducible crystallographic orientation control. Cerenkov-radiation-type waveguide second-harmonic generation is demonstrated. >

Use of thiazole rings to enhance molecular second-order nonlinear optical susceptibilities [Erratum to document cited in CA113(24):220726h

ADVERTISEMENT RETURN TO ISSUEPREVArticleUse of thiazole rings to enhance molecular second-order nonlinear optical susceptibilities [Erratum to document cited in CA113(24):220726h]C. W. Dirk, H. E. Katz, M. L. Schilling, and L. A. KingCite this: Chem. Mater. 1991, 3, 1, 207Publication Date (Print):January 1, 1991Publication History Published online1 May 2002Published inissue 1 January 1991https://doi.org/10.1021/cm00013a041RIGHTS & PERMISSIONSArticle Views46Altmetric-Citations2LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (59 KB) Get e-Alerts Get e-Alerts

Use of thiazole rings to enhance molecular second-order nonlinear optical susceptibilities

Use of thiazole rings to enhance molecular second-order nonlinear optical susceptibilities

Second-order nonlinear optical susceptibility of a quantum well with an applied electric field.

The second-order nonlinear optical susceptibility of a quantum well with an applied electric field is studied theoretically with use of both a parabolic-band model and a valence-band-mixing model. The electronic properties of the asymmetric quantum-well system due to an applied electric field and their effects on the second-order nonlinear susceptibility are illustrated. It is shown that the applied electric field may change the second-order susceptibility significantly. The dispersion of the nonlinear susceptibility using the valence-band-mixing model also shows more features than that using the simple parabolic-band model of previous studies of quantum-well systems.

Optical and nonlinear optical properties of 4-(N,N-dimethylamino)-3-acetamidonitrobenzene single crystals

A method of growing high quality 4-(N,N-dimethylamino)-3-acetamidonitrobenzene (DAN) single crystals is presented. Crystal plates with dimensions of up to 10×5×2 mm3 were produced and optically characterized. The transparency region extends from 485 to 2270 nm. Large birefringence and strong dispersion of the refractive indices were measured allowing two branches of type I and two of type II phase-matched second-harmonic generation. From effective second-order nonlinear optical susceptibilities measured along the branches all nonlinear susceptibilities were evaluated, the highest being d23 =(50±15) pm/V.

Large-scale quantum well domain structures

New structures, based on asymmetric quantum wells, large-scale quantum well domains (LSQWDs) are proposed. Different implementations of LSQWDs are evaluated. The importance of LSQWDs specific property of orderly reversal of second-order nonlinear optical susceptibility for applications in integrated optics is shown. Examples of LSQWD-based devices are given.

Exceptional Second-Order Nonlinear Optical Susceptibilities in Organic Compounds

Abstract Molecular second-order nonlinear optical susceptibilities (β) of donor-acceptor substituted organic compounds compunds were measured in dimethyl sulfoxide solution using electric fields induced second harmonic gneration. The experimental data and theoretical interpretations of the trends led to compounds with values of β useful for imparting high bluk susceptibilities on polymeric materials. Exceptionally high values of β were reached relative to analogues of similar size through the use of tricyanovinyl and dithiolylidenmethyl substituents.

Second-harmonic generation in Langmuir–Blodgett monolayers of stilbazium salt and phenylhydrazone dyes

The second-order nonlinear optical susceptibilities χ(2) of several phenylhydrazone and stilbazium salt dyes in Langmuir–Blodgett monolayers have been determined from second-harmonic-generation measurements. Three of the substances demonstrated χ(2) values greater than 10−6 electrostatic units, although two of the three did not absorb light significantly at the second-harmonic wavelength.

Greatly enhanced second-order nonlinear optical susceptibilities in donor-acceptor organic molecules

Greatly enhanced second-order nonlinear optical susceptibilities in donor-acceptor organic molecules

Optimization of Second Order Nonlinear Optical Susceptibilities in Organic Materials

ABSTRACTMolecular second-order nonlinear optical susceptibilities (β) based on EFISH measurements in dimethylsulfoxide of selected donor-acceptor substituted organic compounds are reported. Enhanced values were noted for compounds containing highly ionizable substituents. Compounds possessing the highest susceptibilities were dissolved in polymer films and electric-field poled, leading to corresponding enhancements in the nonlinear optical coefficients. The data are consistent with molecular and thermodynamic models.

Second-order susceptibility and parametric dispersion in noncentrosymmetric crystals

With use of a quantum-mechanical model based upon the parity indefiniteness of the eigenfunctions associated with different energy eigenstates of a two-level system in noncentrosymmetric crystals, the second-order nonlinear optical susceptibility ${\ensuremath{\chi}}^{(2)}$ has been investigated in III-V semiconductors possessing zinc-blende type of crystal structures. The behavior of ${\ensuremath{\chi}}^{(2)}$ over a wide frequency range from much below the crystal band gap to much above it has been examined analytically. A higher value of ${\ensuremath{\chi}}^{(2)}$ at radiation frequency (${\ensuremath{\omega}}_{0}$) lower than the transition frequency (${\ensuremath{\omega}}_{\mathrm{ng}}$) is noticed. ${\ensuremath{\chi}}^{(2)}$ is found to be larger by some orders in the near-resonant transition regime. A change in the sign of ${\ensuremath{\chi}}^{(2)}$ is predicted for the situation ${\ensuremath{\omega}}_{1}\ensuremath{-}{\ensuremath{\omega}}_{\mathrm{ng}}l0$; ${\ensuremath{\omega}}_{0}g{\ensuremath{\omega}}_{\mathrm{ng}}$, ${\ensuremath{\omega}}_{1}={\ensuremath{\omega}}_{0}\ensuremath{-}{\ensuremath{\omega}}_{s}$; ${\ensuremath{\omega}}_{s}$ and ${\ensuremath{\omega}}_{1}$ being the acoustic frequency and the frequency of the parametrically scattered electromagnetic mode, respectively. Parametric dispersion of electromagnetic and acoustic waves is also studied with use of the semiclassical treatment. The origin of parametric coupling is found to be in the second-order-induced polarization, which can have finite and considerable value only when the noncentrosymmetric crystal is irradiated by a high-intensity pulsed laser beam.

Dispersion of the nonlinear second-order optical susceptibility of organic systems

Dispersion experiments of the second-order nonlinear optical susceptibility are reported for two fundamentally important organic systems $p$-nitroaniline and 2-methyl-4-nitroaniline for which detailed quantum-mechanical calculations have been completed. The frequency-dependent measurements were performed by dc-induced second-harmonic generation in liquid solutions with the use of a tunable (0.2-2 \ensuremath{\mu}m) laser source by stimulated Raman scattering from hydrogen gas. Accounting for dipole-mediated interactions between the molecular sites and the surrounding solvent medium provides quite satisfactory agreement between the experimental and theoretical results, demonstrating that the origin of exceptional nonlinear optical responses of organic systems resides in special highly charge-correlated electron states.

The measurement of the antisymmetric components of nonlinear optical susceptibilities of TeO2 crystal

The antisymmetric components of the second-order nonlinear optical susceptibility of TeO2 crystal have been measured by the process of sum-frequency mixing between the laser beams at the wavelengths of 1.064 and 0.532 μm. The experimental results were χ123/ (χ123+χ132) =0.59, χ132/(χ123 +χ132) =0.41, and χ312/(χ123+χ132) =−χ321/(χ123+χ132) =−0.18, which imply that χ123 and χ132 are slightly asymmetric and χ312 and χ321 are antisymmetric in the second and third suffices. It is thus concluded that the contribution of the antisymmetric component to the signal at the sum frequency may be comparable with that of the symmetric one forbidden by the Kleinman symmetry relation. Moreover, the symmetric and antisymmetric components of the nonlinear optical polarizabilities of the bond Te-O have been estimated in terms of the scheme of bond additivity by assuming a bond symmetry ∞.