Second-order nonlinear optical properties

Second-order nonlinear optical properties describe the coupling interaction between two electric fields (as described in Equation 3.129) and the crystal. For the ideal wurtzite ZnO, with the 6 mm symmetry, there are four nonvanishing second-order nonlinear susceptibility tensor elements, = Xm- and 

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Acentricity greatly enhances the y-value (see 92 vs 91 and 90 or 101 vs 99 and 100, Fig. 8). Such a trend had been predicted for certain ranges of compounds by theory [137] however when the first hyperpolarizability, which determines second-order nonlinear optical properties, is maximized, y is predicted to be zero [138]. 

Bella SD (2001) Second-order nonlinear optical properties of transition metal complexes. Chem Soc Rev 30 355-366... 

A synthesis and physicochemical characterization, including molecular second-order nonlinear optical properties, of new push-pull-based chromophores 170 properly functionalized for polymerization and containing oxadiazole rings were reported <2002J(P2)1791>. 

A specific set of experiments which must be mentioned, being directly associated with the main topic of this paper, is the work of Bergman, et. al. (22) dealing with the second-order nonlinear optical properties of polyvinylidene fluoride (PVF2). Nonvanishing the second-order nonlinear electric dipole susceptibility, is expected in PVF2 since it exhibits other properties requiring noncentrosymmetric microscopic structure. These properties appear... 

The large molecular hyperpolarizability of the merocyanine chromophore (4,5) and the highly polar environment of the quasicrystals has prompted studies of the second order nonlinear optical properties of these materials (6). 

Any symmetry operation is required to leave the sign and magnitude of physical properties unchanged and therefore y xxx = 0. The same line of reasoning can be used to show that all tensor components will vanish under inversion. Hence, second-order nonlinear optical properties are not allowed in centrosymmetric media using the electric dipole approximation. The presence of noncentrosymmetry is one of the most stringent requirements in... 

Donor- and Acceptor-Substituted Organic and Organometallic Compounds Second-Order Nonlinear Optical Properties... 

Gibson, H.W. Guzy, M.T. Shah, S. Wang, H. Neyman, P.J. Van Cott, K.E. Davis, R.M. Figura, C. Brands, C. and Heflin, J.R. (2001) Second-order nonlinear optical properties of ionically self-assembled films, Polymeric Materials Science Engineering of Composite Materials 84, 251-252. 

However, non-centrosymmetry does not automatically imply a dipolar molecule, or, more generally, vectorial properties. Also molecules without a dipole moment can exhibit second-order nonlinear optical properties. Tetrahedral molecules, such as CC14, and trigonal molecules, such as BC13, also lack centrosymmetry. However, they cannot be oriented in an electric field, due to the absence of a dipole moment. Therefore, they can simply not be measured by EFISHG. Also ionic species cannot be measured, since these migrate, rather than rotate, under the influence of an applied field. 

Several papers and patents deal with the preparation of pyrrole-, indole-, and carbazole-derived dyes for application in organic laser device production, coloring of textiles and other materials, photography, analytical chemistry and physiological and organ function monitoring. Sulfonyl-substituted 2-[4-(dialkylamino)phenyliminomethyl]pyrrole dyes have been prepared, for example, 50-53, and their ultraviolet-visible (UV-Vis) absorptions, second-order nonlinear optical properties, and thermal stabilities have been described <1999TL2157>. 

The second-order nonlinear optical properties of the poled film are investigated using second harmonic generation in transmission. The sample preparation technique results in a poled glassy film possessing a unique axis in the direction parallel to the field direction within... 

Tatsuura et al. employed the earlier mentioned E-CVD process to deposit polyazomethine conjugated polymer films with second order nonlinear optical properties. The monomers used were 4-methoxy-o-phenylenediamine (MPDA) ando-phtalaldehyde (o-PA). Ortho-type monomers were used to ensure a total dipole moment for the polymer in the direction perpendicular to the chain. Figure 22 shows the structure of the monomers and the resultant polymer. 

Second order, polyazomethine possesses both donor and acceptor groups at the molecular level, which when aligned gives a poled polymer. Tatsuura et al. fabricated an as-deposited poled polymer film by applying anin-situ electric field during CVD and reported on the second order nonlinear optical properties of the obtained film. The polymer film refractive index was reported to be about 1.68 at 632.8 nm. Second order NLO susceptability, p, was found to be... 

Nakatani, K. and Delaire, J.A. (1997) Reversible photoswitching of second-order nonlinear optical properties in an organic photochromic crystal. Chem. Mater., 9, 2682-2684. 

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