Third-order NLO effects

Third-Order Nonlinear Polarization of Matter and Third-Order NLO Effects... 

TABLE 11.6 Examples of second and third-order NLO effects... 

The third-order NLO effects are described by xi. i) susceptibility on macroscopic level and by second hyperpolarizability y tensor on microscopic one. In contrary to the second order NLO effects the third order effects are present in all molecules and in bulk materials. There exists also a similar relationship between die corresponding bulk susceptibilities and the molecular hyperpolarizabilities as in the... 

X quantifies all second-order NLO effects such as SHG, electro-optic effect (Pockel) and frequency mixing, x is representative of third-order NLO effects such as THG, optical Kerr effect and two-photon absorption (TEA). The real part of 7 describes the nonlinear refractive index and its imaginary part the two-photon cross section (<72). 

Third-order NLO effects, of interest for potential applications, for example in optical limiting ° impose no symmetry constraints. Thus, studies on this type of nonlinearity have addressed both homoleptic and heteroleptic 1,2-dithiolene complexes. Among the members of the former class, study on TBA salts of monoanionic nickel Al5(l,2-dithiolene) complexes with ligands such as phdt , dddt , pddt , cddt, and -substituted 1,2-diphenyl-1,2-ethyl-enedithioate ° have been published. Underhill and co-workers have reported on the nonlinear properties of unsymmetrically substituted w(l,2-dithiolene) complexes, such as iw[l-butyl-2-phenylethene-l,2-dithiolato(2 )-S,S ]nickel(II), embedded in PMMA-based composites (PMMA=polymethylmethacrylate), or in sol-gel materials.As regards the latter class, some works have dealt with complexes containing mnt and dmit ligands. ... 

Third-order NLO effects are described by the macroscopic term 9- (49.2). As in the case of second-... 

Based on Eq. (2), all materials. Including gases, liquids, and solids, can show third-order NLO effects. In contrast to the third-order NLO materials, second-order NLO materials require a noncentrosymmetric alignment of NLO molecules. In the case of SHG, the relationship between the molecular and bulk NLO properties can usually be described as [ 1IJ... 

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