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Third-harmonic Generation (third-harmonic + generation)

Distribution by Scientific Domains

Chemistry	100%

Selected Abstracts

J-aggregation visualized with two-photon-resonant third-harmonic generation

JOURNAL OF RAMAN SPECTROSCOPY, Issue 12 2003
D. A. Akimov
Abstract Third-harmonic generation (THG) with a two-photon-absorption (TPA) type resonance was used to monitor the J-aggregation of ethyl thiacarbocyanine in aqueous solution. Correlations between TPA-resonant THG and two-photon-excited photoluminescence are revealed, indicating the significance of excited states for non-linear-optical processes in J-aggregating solutions. Similar to Raman resonances in coherent anti-Stokes Raman scattering, TPA resonances in THG allow THG enhancement to be effectively decoupled from the growth of radiation losses. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Refractive index and third-order nonlinear susceptibility of C60 in the condensed phase calculated with the discrete solvent reaction field model

INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 5 2005
L. Jensen
Abstract We have calculated the frequency-dependent refractive index and the third-order nonlinear susceptibility for C60 in the condensed phase, which is related to third-harmonic generation (THG) and degenerate four-wave mixing (DFWM) experiments. This was done using the recently developed discrete solvent reaction field (DRF) model, which combines a time-dependent density functional theory (TD-DFT) description of the central C60 molecule with a classical polarizable MM model for the rest of the fullerene cluster. Using this model, effective microscopic properties can be calculated that, combined with calculated local field factors, give macroscopic susceptibilities. The largest calculation was for a cluster of 63 C60 molecules in which the central molecule was treated with TD-DFT. For this molecule, the effective polarizability was increased with about 15% and the effective second hyperpolarizability with about 60% compared with the gas phase. The calculated refractive index was found to be in good agreement with experiments and other theoretical results. The agreement with THG experiments was within a factor of two, whereas for DFWM the agreement was less good due to the neglect of vibrational contributions in the calculations. It was found that it is more important to account for the dispersion in the third-order susceptibilities than in the corresponding second hyperpolarizability. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005 [source]

Anomalous behavior of the second and third harmonics generated by femtosecond Cr:forsterite laser pulses in SiC,polymer nanocomposite materials as functions of the SiC nanopowder content

JOURNAL OF RAMAN SPECTROSCOPY, Issue 12 2003
S. O. Konorov
Abstract Femtosecond pulses of 1.25 µm Cr:forsterite laser radiation were used to study second- and third-harmonic generation in silicon carbide nanopowders embedded in a poly(methyl methacrylate) (PMMA) film. Harmonic generation processes extend the analytical and sensing abilities of light-scattering techniques, including Raman spectroscopy, offering a convenient and efficient approach to the analysis of nanocomposite materials where nanoparticles tend to agglomerate, masking informative features in Raman spectra. The second- and third-harmonic yields are shown to display an anomalous, counterintuitive behavior as functions of the SiC nanopowder content in a polymer film. Whereas harmonic generation in polymer films with a high content of SiC nanocrystals is quenched by the absorption of agglomerating nanoparticles, the influence of absorption is less detrimental in nanocomposite films with a lower SiC content, leading to the growth of the second- and third-harmonic yields. Nanocomposite films with a lower SiC content are also characterized by a higher breakdown threshold, allowing pump pulses with higher fluences to be applied for more efficient harmonic generation. Copyright © 2003 John Wiley & Sons, Ltd. [source]