Design of a high-precision Z-scan measurement system based on a virtual instrument

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.