- Singer K.D. (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 moreWe describe improvements to the Kleinman-disallowed hyper-Rayleigh scattering (HRS) measurement technique, which can be used to measure all of the rotationally invariant figures of merit for the first molecular nonlinear optical hyperpolarizability tensor βijk. As multiphoton excited fluorescence continues to be an accuracy-limiting factor in any HRS experiment, we have implemented time-resolved single photon counting in HRS using a Ti:sapphire laser. We show, however, that spectral analysis is necessary to ensure that the fluorescence and second harmonic are emitted on different time scales in order to allow temporal separation and thus improved accuracy. We also demonstrate how an electrically controlled liquid-crystal phase retarder can be used to vary the polarization state of the probe light in order to determine the second-order nonlinear response tensor. It was found that results agree with those obtained using a rotating quarter-wave plate to control the polarization state and demonstrate improved precision and reproducibility. © 2008 Optical Society of America.
Show less
Show moreThe spectral content of hyper-Rayleigh scattering (HRS) was studied with solutions of disperse red-1 (DR1) in acetone at a specific fundamental wavelength. Dephasing can occur when the effective lifetime of the virtual state approaches a two-photon resonance. Experiments were developed that will measure all six observables in HRS by observing the scattering at 45°, continuously varying the phase of the fundamental by rotating a quarter-waveplate, and using another quarter-waveplate with a linear polarizer to analyze the harmonic. These experiments proved the validity of Kleinmann symmetry in near-resonant and far off-resonant regimes. In any electronic posting permitted by this Section 8.1.9, the following copyright notice must be displayed on the initial screen displaying IEEE-copyrighted material: "©1997 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works."
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 moreSecond-order nonlinear optical (NLO) polymers, which polymers are functionalized with second-order NLO chromophores, offer advantages of large susceptibilities, high laser damage threshold, faster response time, a high density of NLO moieties, versatility of molecular structural modifications, improved processability and relatively higher thermal stability compared with small molecular weight organic materials. The design, synthesis and characterization of novel elastic-polymer containing NLO chiral conjugated chromophores based on the derivatives of chiral camphorquinone, which would be expected to display large three dimensional polarity and more thermal stable NLO optical materials are discussed.
Show less
Show moreWe have designed a hyper-Rayleigh scattering scheme to measure six scalar invariants of the squared hyperpolarizability tensor β2. Our theoretical approach expresses the rotational invariants of the irreducible β components as scalars, which eliminates the need for difficult frame transformations. We applied our scheme to several conjugated chiral molecules and found that there are significant Kleinmann-disallowed pseudotensor contributions to their hyperpolarizability. These components, along with a large optical rotation and the results of quantum-chemical calculations, indicate a handed nonplanar delocalization of the charge-transfer system in such molecules as predicted by quantum-chemical calculations and are expected to lead to macroscopic second-harmonic generation in axially aligned polymer materials. Pseudotensor contributions to the hyperpolarizability in chiral molecules were found to be as large as the vector contribution in p-nitroaniline. We qualitatively investigated the dispersion in the Kleinmann-disallowed components and confirmed that these components are smaller at longer wavelengths. © 1998 Optical Society of America.
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 moreA tunable source is used to study the competition between hyper-Rayleigh scattering (HRS) and multi-photon fluorescence in the detected signal near the second-harmonic by examining the spectral content of the scattered light and its dispersion in the infrared. It is found that even at frequencies noticeably lower than half that of the linear absorption, there is a rapid decrease in the HRS peak and rapid increase in two photon fluorescence. This is attributed to dephasing of the virtual excited state. This transition occurs far from the resonance peak. Two compounds, p-nitroaniline and disperse red 1, are studied, showing that accurate internal referencing can be carried out by considering the symmetry of the solvent to yield accurate measurements of the first hyperpolarizability.
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 describe a new approach to second-order nonlinear optical materials, namely quadrupoling. This approach is valid in the regime of Kleinman (full permutation) symmetry breaking, and thus requires a two- or three dimensional microscopic nonlinearity at wavelengths away from material resonances. This "quadrupolar" nonlinearity arises from the second rank pseudotensor of the rotationally invariant representation of the second-order nonlinear optical tensor. We have experimentally investigated candidate molecules comprised of chiral camphorquinone derivatives by measuring the scalar invariant associated with the rank two pseudotensor using hyper-Rayleigh scattering. We have found sizable scalar figures of merit for several compounds using light for which the second harmonic wavelengths are greater than 100 nm longer than the absorption peak location. At these wavelengths, the quadrupolar scalar is as large as the polar (EFISH) scalar of p-nitroaniline. Prospects for applications are discussed. Citation format: Hubbard S.F, Petschek R.G., Singer K.D., D'Sidocky N., Hudson C., Chien L.C., Henderson C.C., Cahill P.A., ""Quadrupoled" materials for second-order nonlinear optics," Proceedings of SPIE - The International Society for Optical Engineering 3147, 41-52, 1997. Copyright notice format Copyright 1997 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 moreAn oriented gas model for the second-order nonlinear optical response for optical second-harmonic generation in axially aligned nonlinear optical chromophores in chiral media is presented. Design criteria for the alignment of chromophores possessing Kleinman-disallowed traceless symmetric second-rank tensor hyperpolariz-abilities ß resulting in large nonlinear optical susceptibilities χ(2) are enumerated. These chromophores could be oriented in high-density, highly ordered structures due to the absence of dipolar interactions resulting in exceptionally large χ(2) values. The alignment of chromophores that have C2v or Dn (n > 2) symmetry in two chiral nonpolar symmetry groups for the medium, D∞ and D2, are considered. Criteria for response optimization and several physical examples are described. Additionally, certain nonpolar symmetry groups for the medium, of which the most easily realizable is probably D2also admit Kleinman-allowed octupolar susceptibilities for which the optimum chromophore alignment is discussed. © 2001 Optical Society of America.
Show less
Show moreWe have used a high-intensity tunable picosecond infrared laser source to measure the spectral content of light scattered near the second harmonic for two well-known organic dyes, p-Nitroaniline and Disperse Red 1, at a number of wavelengths in the near infrared. We found that in Disperse red 1 a broad two-photon fluorescence competes with the sharp hyper-Rayleigh peak. Further, dephasing of the virtual excited state leads to elimination of hyper-Rayleigh scattering in favor of fluorescence if the harmonic is in the linear absorption tail. We determined the dispersion of the magnitude of the first hyperpolarizability for both dyes, using a simple referencing technique, and found it to be consistent with that of a two-level dispersion model. © 1996 Optical Society of America. This paper was published in Optics Letters and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: [http://www.opticsinfobase.org/ol/abstract.cfm?URI=ol-21-21-1774]. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law.
Show less
Show moreThe synthesis of several new truxenones and one tris(dicyanomethylene) derivative substituted by different amines at positions 4, 9, and 14 is reported. A complete characterization of the NLO properties of representative derivatives was carried out by hyper-Rayleigh scattering; the major electronic effects and the influence of the structural modifications on the NLO properties have been examined. Because of their C3 symmetry and their large first hyperpolarizability, the chiral versions of the tris(dicyanomethylene) truxene derivatives are of interest for second-order nonlinear optics in uniaxially aligned chiral media. © 2006 American Chemical Society. Appropriate credit for the requested material should be given as follows: "Reprinted (adapted) with permission from Chemistry of Materials 18:18, 4259-4269. Copyright 2006 American Chemical Society."
Show less
Show moreWe report the design, synthesis and characterization of novel conjugated chiral materials, based on the derivatives of camphorquinone as shown below, for nonlinear optics. Several conjugated chiral monomers have been prepared and characterized. A x-ray single crystal study was also performed on one of the chiral monomer. The chiral conjugated polymers were prepared from polycondensation of conjugated chiral diolmonomer with di-functional and multifunctional co-monomers. We present results of synthesis and characterization of the conjugated chiral materials. Appropriate credit for the requested material should be given as follows: "Reprinted (adapted) with permission from ACS Symposium Series 795, 77-89. Copyright 2001 American Chemical Society."
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