极化聚合物薄膜取向有序度及极化寿命的表征

Characterizations for Order Parameter and Poled Lifetime of Poled Polymer Film

研究了极化聚合物薄膜波导的退极化过程，提出了表征极化聚合物薄膜取向有序度和极化寿命的集成光学方法。采用集成光学中的棱镜耦合技术，测量极化前后聚合物薄膜光波导的各向异性有效折射率。通过求解各向异性介质光波导的模式本征方程，得到波导极化前后寻常光和非寻常光折射率的变化及其随时间衰减，进而得到取向有序度随时间的变化曲线。采用复合指数函数模型进行最小二乘曲线拟合，进而推测其极化寿命。实验中以键合型ＤＡＮＳ极化聚合物薄膜波导为例，叙述了波导制备和极化过程，给出了波导寻常光和非寻常光折射率随时间变化曲线以及取向有序度随时间变化曲线。通过对取向有序度随时间变化曲线进行最小二乘曲线拟合．确定其极化寿命约为１３４４天。

The process of poling decay with time for poled polymer film waveguides was studied, and an integrated optical method to characterize the order parameter and the poled lifetime of the film waveguides was presented in this paper. The side-chain DANS (4-dimethylamino-4'nitro-stlibene) polymer (50% in weight) and the indium tin oxide-(ITO-) coated glass slides were selected as the waveguide material and the substrates, respectively. The cover layer was air. The DANS polymer film waveguides with suitable thick were made by spin coating. Then the films were poled with the corona-poling setup, which had tungsten wire electrode that was parallel to the surface of the waveguide and along the travelling direction of light in the waveguide. The Poling temperature was 130t, the Poling voltage was about 5 - 7kV, the Poling current was about 2uA, the poling time was 30min and the space between the surface of the waveguide and the electrode was 9mm. Before and after Poling, the anisotropic effective refractive indices were measured using prism coupling technique in the field of integrated optics. The variety of the ordinary and the extraordinary refractive indices before and after poling and their decay with time were derived from the anisotropic mode eigen-equations, and then curves of the ordinary and the extraordinary refractive indices varied with time were obtained. The curve of the order parameter varied with time was presented and fitted with the multiple exponential function using the least square method. It was determined that the poled lifetime is about 1344 days.