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

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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.