- text (x)
- Twieg R.J. (x)
- Search results
Search results
Show moreQuadrupolar and octupolar invariants may be used as methods to attain noncentrosymmetric materials for application in second order nonlinear optics. The structure-property relationships for the J = 2, or quadrupole rotational invariant, are investigated. Proper citation for the Technical Digest CD-ROM should be written in the following format: Ostrovekhov V., Ostroverkhova O., Petschek R.G., Singer K.D., Sukhomlinova L., Twieg R.J., “`Quadrupolar' molecular nonlinear optics,” in the Conference on Lasers and Electro-Optics (CLEO)/The International Quantum Electronics Conference (IQEC) (Optical Society of America, Washington, DC, 2009), Proceedings, 8-9
Show less
Show moreOrganic chromophores have been exploited for a wide range of discrete optical and electronic functions as well as a growing number of combined opto-electronic functions. We are pursuing development of organic and polymer materials for a range of applications that require properties including liquid crystallinity, second order optical nonlinearity, photorefractivity and, more recently, special nonlinear optical behavior involving molecular chirality. On publication the full bibliographical details of the paper (Proceedings 561(1999), 119-130) must be inserted after the journal title, along with a link [http://journals.cambridge.org/abstract_S1946427400208403] to the Cambridge website address for the journal. Inclusion of this version of the paper in Institutional Repositories outside of the institution in which the contributor worked at the time the paper was first submitted will be subject to the additional permission of Cambridge University Press (not to be unreasonably withheld).
Show less
Show moreWe describe improvements to a previously reported hyper-Rayleigh scattering technique [J. Opt. Soc. Am. B 15, 289 (1998)], for measuring all rotational invariants of the first hyperpolarizability tensor. The full hyper-Rayleigh scattering tensor is expressed in terms of its rotatior.ally invariant components leading to a figures of merit corresponding to each of the rotationally invariant tensors. With elliptically polarized incident light, the polarization state and the intensity of the harmonic light are measured at a scattering angle of 45°. A new analytical fitting method is applied to the signal for two polarization measurements to yield the invariants. We have measured several chiral and nonchiral chromophores to determine the hyperpolarizability tensor with which to analyze the measurement accuracy, to reveal structure property relationships, and to assess the applicability of the chromophores as nonlinear optical materials. Results for a series of chiral chromophores and for Crystal Violet are presented. © 2000 Optical Society of America.
Show less
Show moreTime-resolved single photon counting is used for measuring Kleinman-disallowed nonlinear tensor components in order to evaluate molecular materials for chiral axial organic nonlinear optical materials. The experimental setup and results are described. © 2004 Optical Society of America.
Show less
Show moreThis article reviews our work on the development and optimization of chiral, nonpolar media with large second-order nonlinear optical responses. We show how molecular engineering, theory, and measurements can be used to optimize this promising class of nonlinear optical materials. We describe how supramolecular alignment into easily processable materials takes advantage of the relevant molecular hyperpolarizabilities. A wide variety of techniques can be used to fabricate bulk materials belonging to the chiral nonpolar symmetry groups, D∞ and D2. The microscopic chromophore alignment schemes that optimize the nonlinear optical response in such materials are deduced from general symmetry considerations for both molecules and bulk. We also speculate on the possible applications of such materials as image-plane modulators. After publication of the final article, the right to self-archive on the Contributor's personal intranet page or in the Contributor's institution's/ employer's institutional intranet repository or archive. The Contributor may not update the submission version or replace it with the published Contribution. The version posted must contain a legend as follows: This is the pre-peer reviewed version of the following article: Journal of Polymer Science, Part B: Polymer Physics 41:21, 2744-2754, which has been published in final form at http://onlinelibrary.wiley.com/doi/10.1002/polb.10655/full
Show less
Show moreMolecular properties leading to second harmonic generation in chiral media in the electric dipole approximation for the cases of axial and biaxial symmetry are described. The components of the hyperpolarizability tensor that transform like a second-rank pseudotensor (L = 2) and a third-rank tensor (L = 3) contribute. The sum-over-states quantum formula for the hyperpolarizability is used to illuminate the molecular features necessary for optimizing the second-rank pseudotensor for dipolar molecules including orthogonal moments and high frequency. The example of C2(v), appropriate for A-shaped molecules, is examined in more detail. Results of the measurements of these components in representative molecules using hyper-Rayleigh scattering are presented. Two compounds in which the delocalized pi-system is two-dimensional, a camphorquinone derivative and crystal violet are found to exhibit sizable L = 2 and L = 3 components. (C) 2000 Elsevier Science B.V.
Show less
Show moreThis paper describes the development and optimization of chiral, non-polar media with large second-order nonlinear optical responses. We employ molecular engineering, quantum-mechanical sum-over-states theory, and measurements of molecular hyperpolarizability by means of Kleinman-disallowed hyper-Rayleigh scattering in order to understand molecular properties. Then we analyze the appropriate arrangement of the chromophores that produce an optimum axial nonlinear optical medium. Chromophores with large Kleinman disallowed traceless symmetric second rank tensor hyper-polarizabilities β can be aligned so as to result in large susceptibilities, (2), in structures that lack polar order. We found that Λ-shaped chromophores with C2v or similar symmetry are good candidates for these materials as they can exhibit large second-rank components of the hyperpolarizability tensor. A wide variety of techniques can be used to fabricate bulk materials belonging to the chiral non-polar symmetry groups, D∞ and D2. The microscopic chromophore alignment schemes that optimize the NLO response in such materials are deduced from general symmetry consideration for both molecules and bulk. Citation format: Ostroverkhov V., Ostroverkhova O., Petschek R.G., Singer K.D., Sukhomlinova L., Twieg R.J., "Optimization of the nonlinear optical response in chiral media," Proceedings of SPIE - The International Society for Optical Engineering 4279, 25-36, 2001. Copyright notice format Copyright 2001 Society of Photo Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.
Show less
Show moreThis paper describes the development and optimization of chiral, nonpolar media with large second-order nonlinear optical responses. We employ molecular engineering, quantum-mechanical sum-over-states theory, and measurements of molecular hyperpolarizability by means of Kleinman-disallowed hyper-Rayleigh scattering in order to understand molecular properties. Then we analyze the appropriate arrangement of the chromophores that produce an optimum axial nonlinear optical medium. Chromophores with large Kleinman disallowed traceless symmetric second-rank tensor hyperpolarizabilities β can be aligned so as to result in large susceptibilities χ(2) in structures that lack polar order. We found that A-shaped chromophores with C2v or similar symmetry are good candidates for these materials, as they can exhibit large second-rank components of the hyperpolarizability tensor. A wide variety of techniques can be used to fabricate bulk materials belonging to the chiral nonpolar symmetry groups D∞ and D2. The microscopic chromophore alignment schemes that optimize the nonlinear optical response in such materials are deduced from general symmetry consideration for both molecules and bulk. We also speculate on the possible application of such materials as high-bandwidth spatial light modulators. The following IEEE notice should appear prominently on the first page/screen of each reprinted paper, with the appropriate details filled in: © 2001 IEEE. Reprinted, with permission, from Ostroverkhov V., Ostroverkhova O., Petschek R.G., Singer K.D., Sukhomlinova L., Twieg R.J., Prospects for chiral nonlinear optical media, IEEE Journal on Selected Topics in Quantum Electronics, 2001. This material is posted here with permission of the IEEE. Such permission of the IEEE does not in any way imply IEEE endorsement of any of Case Western Reserve University's products or services. Internal or personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from the IEEE by writing to pubs-permissions@ieee.org. By choosing to view this document, you agree to all provisions of the copyright laws protecting it.
Show less
Show moreWe report on the synthesis of new quadripolar triarylmethyl cations related to Crystal Violet and the characterization of their NLO properties by a new hyper Rayleigh scattering (HRS) technique. We have prepared a range of triarylmethyl cations that incorporate one, two or three naphthyl moieties. These structural modifications have a direct influence on the NLO properties that have been determined by the Timed-Correlated Single Photon Counting 45° HRS (TCSP-45-HRS) and also influence absorption properties as seen in the UV-Visible spectra. © 2005 Old City Publishing, Inc. Request granted provided that "full credit to the original publication is given" and the publication is more than 12 months past original publication date
Show less
Show moreCationic triarylmethane dyes containing one, two or three naphthalene moieties have been prepared. Their synthesis and preliminary spectral, nonlinear optical and theoretical characterization are reported here. The major electronic and steric hindrance effects of the 1,4-linked naphthalene have been examined by comparison of the UV-vis absorption of the 1,4-linked and 2,6-linked series. © 2005 Elsevier Ltd. All rights reserved.
Show less
Show moreThe first hyperpolarizability of several Λ-like chromophores including Malachite Green and Brilliant Green were measured by means of Kleinman-disallowed hyper-Rayleigh (harmonic light) scattering (KD-HRS). Such chromophores are of interest as components of a new class of chiral and axial macroscopic materials. Light scattering measurements were carried out in both the non-resonant and the anomalous dispersion regime in order to compare experimental results with a two-level model that indicates that B-symmetry excited states will contribute. Large hyperpolarizabilities were observed in all cases and evidence that the lowest-lying excited state has B-symmetry was found in some molecules. © 2001 Elsevier Science B.V.
Show less