Nonlinear optical properties of organic and polymeric materials
29 Sep 1983-
About: The article was published on 1983-09-29 and is currently open access. It has received 762 citations till now.
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TL;DR: In this paper, the authors 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.
Abstract: 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).
4 citations
TL;DR: In this article, single crystals of (2E, 6E)-2-(4-bromobenzylidine)-6-(4methoxybenzylidine)cyclohexanone are grown by slow evaporation solution growth technique from ethanol at room temperature.
Abstract: Single crystals of (2E, 6E)-2-(4-bromobenzylidine)-6-(4-methoxybenzylidine)cyclohexanone are grown by slow evaporation solution growth technique from ethanol at room temperature. The single crystal-X-ray diffraction study reveals that as-grown crystal belongs to triclinic system and the cell parameters are, a = 9.3720(3) A, b = 11.0500(7) A, c = 18.1790(3) A, and V = 1,734.90(13) A3. The structure and the crystallinity of the material were further confirmed by nuclear magnetic resonance spectroscopy and powder X-ray diffraction analysis. Simulated XRD pattern closely resembles the powder XRD profile with lowered intensities. FT-IR and FT-Raman spectral analyses reveal the various modes of vibrations. The crystal is transparent in the visible region having a lower optical cut-off at ~503 nm with band gap energy of 2.55 eV, estimated by the application of Kubelka–Munk algorithm. Theoretical calculations were performed using the Hartree–Fock method at level with 6-31G(d,p) as the basis set for to derive the optimized geometry and first-order molecular hyperpolarizability (β) values. The as-grown specimens were further characterized by dielectric and mechanical studies.
4 citations
Cites background from "Nonlinear optical properties of org..."
...Another importance of this type of compound is its high photosensitivity and thermal stability which are used in developing various crystalline electro-optical devices [9, 10]....
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01 Oct 2021
TL;DR: In this paper, the vibrational properties of a series of push-pull polyynes have been studied by infrared and Raman spectroscopy, and the properties of these molecules have been investigated with the support of density functional theory calculations, as well as the electronic and vibrational first hyperpolarizabilities (β).
Abstract: The vibrational properties of a series of push-pull polyynes have been studied by infrared and Raman spectroscopy. The simultaneous activation of a strong infrared and Raman mode, i.e. the collective vibration of CC bonds of the sp carbon chain, highlights the effectiveness of a polyyne bridge in promoting charge transfer between the electron donor (D) and acceptor (A) ends, thus suggesting that ad-hoc functionalized polyynes are worth being explored as building blocks of organic materials with attractive first-order optical nonlinearity. The optical, electronic, and vibrational properties of these molecules have been investigated with the support of density functional theory calculations, as well as the electronic and vibrational first hyperpolarizabilities (β). The mid-low region of the IR spectra (800-1600 cm−1) has been analyzed in detail, searching for marker bands of the specific terminations of the different sp carbon chains thus achieving a complete vibrational characterization of sp hybridized push-pull systems.
4 citations
TL;DR: In this article, a theory of orientation Brownian motion of a polar particle frozen in a polymer glass is presented, where a cascade of orientation motions at all time scales results in a stretched-exponential behavior of the nonlinear optical response function and other moments of the angular distribution function.
Abstract: We present a theory of orientation Brownian motion of a polar particle frozen‐in in a polymer glass. The theoretical problem is then one of orientation dynamics in a viscoelastic medium. The glassy material provides, at a short‐time scale, an elastic force that returns the orientation to that at time t=0. On larger time scales, this privileged orientation diffuses due to thermal motion. A cascade of orientation motions at all time scales results in a stretched‐exponential behavior of the nonlinear optical response function and of other moments of the angular distribution function.
4 citations
TL;DR: In this article, an extended Hubbard model for the electrons in the aromatic ring that takes into account the interaction between them and the bonding electrons was proposed. But the model was not applied to the case of benzene, and the experimentally observed magnetic anisotropy was recovered with realistic values of the coupling constants.
Abstract: A well-known property of aromatic molecules is their highly anisotropic response to the presence of an external magnetic field: the component of their magnetic susceptibility parallel to the field is generally much larger than the remaining in-plane components. This intriguing phenomenon is rationalized as a consequence of the delocalization of the itinerant electrons that populate the aromatic ring. In this work, we revisit the magnetism of aromatic molecules and propose an extended Hubbard model for the electrons in the aromatic ring that takes into account the interaction between them and the bonding electrons. We show that the bonding electrons play an important and overlooked role: they mediate an effective, attractive momentum-momentum interaction between the itinerant electrons, which promotes a strong enhancement in the magnetic response of the aromatic ring. For the particular case of benzene, we show that the experimentally observed magnetic anisotropy is recovered with realistic values of the coupling constants.
4 citations