ORGANIC NONLINEAR OPTICAL MATERIAL

The present invention provides an organic nonlinear optical material comprising a benzylidene-aniline derivative having an electron-donating substituent introduced at the 4-position and an electron-accepting substituent introduced at the 4'-position, by following two contrivances: (l) selecting as the conjugated pi electronic system a benzylidene-aniline derivative having a large molecular hyperpolarizability and yet a dipole moment as small as those of benzene derivatives, and (2) introducing a molecular alignment-regulating substituent. The centrosymmetry in the bulk state of the material, for example, in the crystal state, is destroyed and the molecular alignment is regulated to such a bulk structure in that the optical nonlinearity possessed by the molecule is effectively utilized. The material shows even a large optical nonlinearity never attained by the conventional techniques. The intermolecular cohesive force due to the pi electron interaction between the molecules in the present invention is larger than that between benzene derivatives. Consequently, the material has, comparatively, a high melting point, a low subliming property, and a low water-absorbing property. In conclusion, a practically invaluable nonlinear optical material having a high durability in the bulk state and an excellent resistance to laser damage can be provided.