The nonlinear optical property and photoinduced anisotropy of a novel azobenzene-containing fluorinated polyimide

A novel azobenzene-containing fluorinated polyimide was synthesized. The nonlinear optical property and photoinduced birefringence of a polyimide thin film were investigated. Large third-order nonlinear refraction (n 2=−4.49×10−11 cm2/W) was observed in the polyimide thin film by carrying out Z-scan measurement. The polyimide thin film exhibited larger nonlinear refraction than that of a mono-azo dye doped PMMA thin film (n 2=−1.63×10−12 cm2/W). The photoinduced birefringence of the polyimide thin film (▵ n∼10−2) under different pump intensities was investigated; it was much larger than that of the mono-azo dye doped PMMA thin film (▵ n∼10−3). Moreover, the time constants for birefringence growth and relaxation processes were determined.