Development of novel nonlinear optical material based on ferroelectric polymer and their applications to frequency doubler

本研究的目的是设计一种由铁电聚合物主体和非线性光学活性客体如高极性染料分子组成的新型稳定的非线性光学（NLO）客体-主体体系。通过极化铁电体的强内电场使客体取向稳定。首先，研究了80wt%聚偏氟乙烯（PVF）和20wt%聚甲基丙烯酸薄荷酯（MMA）共混物中β晶偶极子择优取向产生的内电场（Ei）对NLO染料二次谐波产生（SHG）的影响。NLO染料优先排列的内部电场所产生的定向β-微晶偶极子。在高于Tg的温度范围内，热释电活性的温度分布与取向的β晶偶极的弛豫相一致。本文<33><31>还制备了甲基丙烯酸甲酯（MMA）与乙烯基单体的共聚物（P（MMA-co-MMA-DRI）），研究了P（VDF-TrFE）/P（MMA-co-MMA-DRI）共混物的倍频活性。共混物的E_i温度分布与热释电温度分布和二次谐波系数d_i温度分布一致<33>。在玻璃化转变温度T_g附近，它们的活性没有明显降低，但在高于T_g的居里转变温度附近，它们的活性急剧下降。讨论了居里转变温度下内电场、热释电性和二次谐波活动的热稳定性与β-晶体偶极子有序-无序转变的关系。

Our goal this study is to design new stable nonlinear optical (NLO) guest-host systems comprising a ferroelectric polymer host and NLO active guest such as highly polar dye molecule. The guest is orientationally stabilized by the strong internal electric field of the poled ferroelectric. The strong internal electric field exists in the amorphous phase where guest resides.First, the second harmonic generation (SHG) activities from NLO dyes oriented by the internal electric field (E_i) created by the preferential alignment of beta-crystallite dipoles in poled blend of 80 wt% poly (vinylidene fluoride) and 20 wt% poly (menthyl methacrylate) has been studied. NLO dyes were preferentially aligned by the internal electric field created by the oriented beta-crystallite dipoles. The nature of the SHG activities loss corresponds well to the relaxation of oriented beta-crystallite dipoles in the temperature region above T_g, which is shared by the temperature profile of pyroelectric activity. SHG coefficients of d_<33> and d_<31> are also investigated as a function of NLO dye concentration.We have also prepared the copolymer of methyl methacrylate (MMA) with vinyl monomer having a NLO pedant amino-nitro-azobenzene (P(MMA-co-MMA-DRI)) as a SHG active polymer, and SHG activities for the blend of P(VDF-TrFE)/P(MMA-co-MMA-DRI) has been studied. Temperature profiles of E_i for the blends are shared by those of pyroelectricity and those of SHG coefficient d_<33>. Their activities are not significantly depressed at the glass transition temperature T_g, but drastically lost at the temperature around Curie transition temperature which is higher than T_g. We discuss the nature of the thermal stability of internal electric field, pyroelectricity and SHG activity, relating to the order-disorder transition of beta-crystallite dipoles at the Curie transition temperature.