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1 December 1990 New organic second-order nonlinear optical crystals of benzylidene-aniline derivative
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The benzylidene-aniline derivative with an electron-donating group at 4-position and an electron-accepting group at 4'-position has been suggested by MO calculation, to have a small molecular dipole moment but a large second-order hyperpolarizability in comparison with those of p-nitroaniline analogous molecules, hence, to be a promising molecule on searching for a new organic crystal with large second-order optical nonlinearity. Chemical modification of the molecule suggested led to a discovery of a series of crystals having high activities in second harmonic generation ( SHG ) ; one of which, 4'-nitrobenzylidene-3-acetamino-4-methoxyaniline ( MNBA ) crystal in monodinic Cc with four molecules per unit cell showed larger powder SHG than 2-methyl-4-mtroaniline ( MNA ) crystal in a preliminary powder SHG experiment. A strongly polarized non-centrosymmetric molecular packing has been achieved in this crystal by the presence of intermolecular hydrogen bond between neighboring acetainino groups. Calculation by an oriented gas model with the use of the detailed structural data from X-ray analysis for the MNBA crystal predicted that the crystal may have up to ca. 2.9 times larger macroscopic optical nonlinearity than MNA crystal. This has been experimentally proven by measuring the d for SHG by Maker fringe method. The largest d coefficient was found to be dii , and the value obtained was 454 pm/V which is 1.8 times larger than d11 of MNA crystal and 13 times larger than of lithium mobate ( ) crystal.
© (1990) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Tetsuya Tsunekawa, Tetsuya Gotoh, Hiroshi Mataki, Toshiyuki Kondo, Seiji Fukuda, and Masao Iwamoto "New organic second-order nonlinear optical crystals of benzylidene-aniline derivative", Proc. SPIE 1337, Nonlinear Optical Properties of Organic Materials III, (1 December 1990);

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