半花菁LB多层膜二次谐波产生的温度特性研究

Investigation on Temperature Properties of Second harmonic Generation in Hemicyanine Langmuir Blodgett Multilayer Films

利用吸收谱和二次谐波产生 (SHG)技术研究了温度对半花菁Langmuir Blodgett(LB)多层膜的膜结构和非线性光学特性的影响。LB膜的二次谐波强度起初随温度的增加而增加 ,最大值约在 45℃左右 ,然后随温度的增加而减小。在半花菁与花生酸或花生酸铬交替的LB多层膜中 ,由于花生酸的融化 ,导致膜结构的变化 ,使得二次谐波强度随温度的变化有一个突变点。线性吸收谱表明半花菁分子在LB多层膜中形成了H 聚集体 。

Molecular structure and optical nonlinearity in interleaving hemicyanine/arachidic acid or cadmium arachidate multilayers, and Z-type pure hemicyanine multilayers were investigated as a function of the temperature by means of second harmonic generation (SHG) and linear absorption. The SHG intensity shows a maximum at about 45° in the multilayers. An inflection was observed in the temperature dependence of SHG intensity in the interleaving hemicyanine/arachidic acid and hemicyanine/cadmium arachidate multilayers, and was attributed to melting of arachidic acid or cadmium arachidate. The absorption spectra show that molecules in the multilayers formed H-aggregates which could be dissociated by heating.