YAG飞秒放大器产生的800 nm的飞秒激光作为探测光，经透镜聚焦后通过薄介质样品; 用数字示波器测量样品在透镜焦点附近的透射光强，经过数据处理得到样品的非线性折射率和非线性吸收系数。利用该实验系统，对标准非线性吸收样品Rhodamine 6B进行了测量，计算得到其双光子吸收截面为σ2=68 GM(GM=10-50 cm4 s photon-1 molecule-1)，该结果与其他文献利用不同测量方法得到的结果接近，证明该实验系统的测量结果是正确的，可满足非线性测量的精度要求。

A sensitive Z-scan measurement system using a femtosecond Nd∶YAG laser(800 nm) as the excited light and based on Labview is reported. Under the control of Labview, the digital oscilloscope TDS3012 and the micro-translation stage are used to measure the light intensity, and the Z-scan function is realized. By taking a 800 nm fs laser from a Nd∶YAG fs amplifier as a detecting light, the two transmittance intensities of light is measured by passing it through a thin nonlinear sample with a digital oscilloscope. Then both the nonlinear refractive index and nonlinear absorption coefficient can be obtained. The nonlinear absorption coefficient of Rhodamine 6B at 800 nm was measured. The results produced a two-photon absorption cross-section of 68 GM(GM=10-50 cm4 s photon-1 molecule-1). The system is shown to be reliable by comparison of our measured results with the those obtained from other different measuring methods.