为了有效地测量有机薄膜的双光子吸收截面，针对较薄有机薄膜（约60 μm）和有限激发光源功率，提出了基于非线性透过率测量法的皮秒激光脉冲激发等效多层膜非线性透过率法来实现双光子吸收截面的测量。首先在PC材料基板上旋涂偶氮染料薄膜，将带有偶氮薄膜的PC基板剪切成小块（20 mm× 20 mm），并将5块叠加起来作为测量样品，然后采用LD泵浦的Nd∶YVO4皮秒锁模激光器（脉冲宽度为20 ps、重复频率为56.8 MHz、输出波长为1 064 nm）激发样品。 在实验中，通过测量样品的非线性透过率，拟合偶氮样品的透过率曲线，最终得到了双光子吸收截面（634.2 GM）。与其他测量方法相比，此方法简单、有效。

In order to measure the Two Photon Absorption(TPA) cross section of organic material films, a new approach to measure the TPA cross section of a azo dye film based on the nonlinear transmission methods by a low power picosecond Nd∶YVO4 laser was presented. Firstly, a multi-layered equivalent film sample(5 layers, 20 mm×20 mm) with the same thickness for each layer was prepared. The film from an azo dye material was spun and coated on a large PC substrate and then it was cut into 20 mm×20 mm clips. Furthermore, a mode-locked Nd∶YVO4 picosecond laser(1 064 nm, 56.8 MHz, 20 ps) was chosen as the pump source to excite the sample. Finally, the nonlinear transmittance of the five-equivalent layer film was measured and the curve of the experimental data was fitted. Obtained result shows the value of the TPA cross section of this dye molecule is 634.2 GM. Compared with other methods, this experimental scheme is very simple and valid.