The Local Field Factor and Microscopic Cascading: A Self-Consistent Method Applied to Confined Systems of Molecules (original) (raw)
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Physical Review A, 1982
Efficiency of three-wave interactions in molecular crystals depends on the conjugation of the molecular unit, which in turn is a one-or two-dimensional property. This strong anisotropy reduces the number of non-negligible molecular lowest-order hyperpolarizability coefficients to four. The lowest-order macroscopic optical nonlinearity can be expressed, in the absence of significant intermolecular effects, as the tensorial sum of molecular hyperpolarizabilities. This analysis is applied to the 17 relevant noncentrosymmetric crystal point groups, generalizing a previous analysis of nonlinear-optical properties of methyl-(2, 4dinitrophenyl)-aminopropanoate crystals. In several cases, the molecular unit anisotropy is shown to impose structural relations between coefficients of macroscopic nonlinearities, in addition to the usual relations resulting from the crystal point symmetry only. In such cases, nonlinear-optics experiments can be used for testing molecular anisotropy and molecular orientations within the unit cell in the absence of significant nonlinearity arising from intermolecular coupling. Similar relations can be derived between electro-optic coefficients, but limited to the case of weak contributions of intermolecular vibration to the electro-optic effect. We investigate for each point group the possibility of inferring hyperpolarizability coefficients from macroscopic nonlinear measurements, a complementary approach to that based on theoretical molecular calculations or electric-field-induced second-harmonic generation in solution. In the case of highly anisotropic one-dimensional charge-transfer systems (exemplified by p-nitroaniline), for each point group and a given molecular hyperpo
Optics Communications, 2002
We report measurements of the third-order nonlinear optical susceptibilities of a novel dyads of C 60 -TTF with saturated (ACACA) chemical bonds in solutions were performed using degenerate four wave mixing (DFWM) technique at k ¼ 532 nm in picosecond regime. The third-order nonlinear susceptibilities values, and the corresponding figures of merits are evaluated. The optical power limiting properties of the mentioned compounds are measured using picosecond laser pulses at the same wavelength k ¼ 532 nm. A correlation between the length of the carbon chain (i.e., the increase of the number of saturated (ACACA) bonds and third-order susceptibilities is found.
Large third-order optical nonlinearities of C60-derived nanotubes in infrared
Chemical Physics Letters, 1997
Garito and coworkers have suggested a mechanism to dramatically increase third-order optical nonlinearities of linear w Ž. x p-electron-conjugated molecules. Very recently, Marder and coworkers Science 276 1997 1233 have tested these ideas experimentally and have got large third-order optical nonlinearities in polarized carotenoids. In this Letter, our theoretical calculations predict that large third-order optical nonlinearities in C-derived nanotubes could be obtained in the infrared, 60 which implies that carbon nanotubes are also important nonlinear optical materials in photonic applications. q 1997 Elsevier Science B.V.
Low- and high-order nonlinear optical characterization of C60-containing media
The European Physical Journal D, 2011
Third-and higher-order nonlinear optical processes in fullerenes were studies to define the influence of low-order nonlinearities on the high-order harmonic generation in these media. We measured the nonlinear absorption coefficients of the C60:toluene solution using the 532 and 1064 nm, 50 ps pulses. The high-order harmonic generation was studied during propagation of the 790 nm, 150 fs pulses through the plasmas produced on surfaces containing fullerene powder. These studies have shown that the low-order nonlinearities of fullerenes have no impact on the generation of harmonics in such mediums in the vacuum ultraviolet range at optimal intensity of laser radiation.
Variations of nonlinear optical characteristics of C60 thin films at 532 nm
Optics Communications, 2003
We present our investigations of the real and imaginary parts of third-order nonlinear susceptibility ðv ð3Þ Þ of C 60 thin films ($100 nm) by the Z-scan technique at the wavelength of Nd:YAG laser second harmonic radiation (532 nm, s ¼ 55 ps). Our studies have shown that the sign of Rev ð3Þ changed from negative (at 2-Hz pulse repetition rate) to positive (at 0.5-Hz pulse repetition rate). Sign variations of the real part of third-order susceptibility were attributed to the influence of thermal lens. The reverse saturable absorption was found to be responsible for the nonlinear absorption. We attribute the high values of Rev ð3Þ ((4.8 AE 1) Â 10 À8 esu) and Imv ð3Þ ((1.1 AE 0.2) Â 10 À8 esu) obtained in these studies to surface-enhanced effect.
Nonlinear Field-dependent Susceptibilities of C60 and Carbon Nanotubes
Australian Journal of Physics
We have found strongly nonlinear, field-dependent magnetic susceptibilities in a range of carbon-based materials such as C60, carbon nanotubes, diamond and graphite. This nonlinear behaviour is prominent at low fields and it vanishes at relatively high fields. We have interpreted this phenomenon in terms of the field dependence of the spectral energy separations of the van Vleck paramagnetic term of the susceptibility. Our results should have significant bearing on the interpretation of the magnetic properties of this class of materials.
Fundamental limits on third-order molecular susceptibilities
Optics Letters, 2000
By the use of sum rules, the largest third-order molecular nonlinear-optical susceptibilities allowed by quantum mechanics are determined. The theoretical upper limit is found to depend only on the first excited-state transition energy and on the number of electrons, in agreement with experimental data.
A macroscopic formalism to describe the second-order nonlinear optical response of nanostructures
Journal of Optics A: Pure and Applied Optics, 2006
We present a macroscopic formalism to describe the second-order nonlinear optical response of nanostructures. Rapid variations in local nonlinearity and electric field distributions on scales smaller than a wavelength preclude a simple, direct relationship between the macroscopic and nanoscopic nonlinear response functions in arrays of metal nanoparticles. We develop an approach that bypasses these difficulties by focusing on the macroscopic nonlinear optical response of the sample in terms of the input and output fields. The main advantage of this macroscopic formalism is that it naturally includes contributions from higher multipoles, although symmetry properties can be addressed using electric-dipole-type selection rules. It is limited by being specific to the experimental geometry, although experimental variations are expected to provide additional insight into the underlying physical processes. The formalism is applied to the second-harmonic response of an array of L-shaped gold nanoparticles.