利用合成的一种新型π共轭聚合物――聚吡咯甲烯为非线性介质，进行激光感应衍射实验，测量材料的非线性折射率。实验发现，当526nm的基模高斯光束通过该聚合物的N-甲基-2-吡咯烷酮(NMP)溶液时，在远场处产生了多个同心衍射圆环。该现象可以用高斯光束通过介质时产生的空间自相位调制解释。经过理论分析和数值计算，发现样品对光束横截面上产生的非线性相移非常近似于高斯分布。通过对非线性相移的高斯曲线拟合及衍射环个数的测量，可以估算出聚吡咯甲烯/NMP溶液的非线性折射率n2～-1.85×10-3esu。

A new type of π-conjugated polymer―Polypyrrylarylenemethine is designed and synthesized, which shows large nonlinear optical characteristics. It is discovered in experiment that as the 526 nm TEM00 laser beam passing through the Polypyrrylarylenemethine/N-Methyl-2-pyrrolidone (NMP) solution, numbers of concentric diffraction rings arise in far field. This phenomenon can be explained by the spatial self-phase modulation of the Gaussian beam passing through the nonlinear medium. With theoretical analysis and numeric calculation, it is found that the transverse nonlinear phase shift caused by the sample can be very well fitted by a Gaussian function. The nonlinear refractive index n2 can be estimated according to the number of the diffraction r ings. The n2 of Polypyrrylarylenemethine/NMP solution is about -1.85×10 -3 esu.