Structural Effects in High-Temperature Electrooptic Chromophores

摘要

We have carried out a theoretical and experimental study of isomeric structural effects on second-order optical properties for two high-temperature structural isomers, SY177 and SY177P. The results showed that although these isomers are very similar in molecular structure, they differ markedly in second-order nonlinear optical properties. Upon virtual excita-tion, the electron-donating amine group in SY177 was found to be an active site in the important charge-separation process, while in sharp contrast, the same group in SY177P, positioned differently on an adjacent carbon site, was found to be relatively uninvolved. Dc-induced second harmonic generation measurements confirmed the theoretical predictions, with more than a factor of 4 difference found in the second-order optical responses between these two isomers. The microscopic second-order β_x(-2ω;ω,ω) at λ = 1907 nm (0.65 eV) was measured to be 93 x 10~(30) esu for SY177 and 21 x 10~(-30) esu for SY177P in dioxane solution.