| 摘要 |
PURPOSE:To obtain an org. nonlinear optical material capable of executing nonlinear optical response at high speed and high efficiency by selecting an org. nonlinear optical material having small polarization in the ground state and regulating electron cloud in the excited state to have a center of symmetry. CONSTITUTION:The title optical material is expressed by formula I, wherein D is an electron donative group; at least one of R1 and R2 is a group other than H; Xn is 1-4 substituting halogen. Spontaneous polarization of the whole molecule is nullified by substituting both terminal atoms of a relatively long pi-conjugated molecule by strong doners having a same structure, and the charge density of the pi-conjugated part is increased in only the excited state by halogenating a central phenylene group. Thus, the difference of charge transfer between the ground state and the excited state is enlarged. By this constitution, decrease of response speed is prevented by preventing the absorption wavelength from transferring to long wave side, and great tertiary nonlinear optical effect is attained simultaneously. |
