Shui Min, Luo Xinyu, Zhang Xueru, Jin Xiao, Li Changwei, Yang Junyi, Li Zhongguo, Shi Guang, Yang Kun, Wang Yuxiao, Song Yinglin
Department of Physics, Harbin Institute of Technology, Harbin 150001, China.
J Opt Soc Am A Opt Image Sci Vis. 2010 Nov 1;27(11):2514-23. doi: 10.1364/JOSAA.27.002514.
Using the nonlinear-imaging technique with a phase object (NIT-PO), we have studied third-order nonlinearities of various samples. In this work, we develop, for pure nonlinear refractive materials, an approximate method to calculate the nonlinear refractive coefficient analytically. By decomposing the object field passing through the phase object into two top-hat beams of different phases and beam radius, we acquire the approximate phase contrast, from which we extract the nonlinear refractive coefficient. This approximation is valid when the on-axis nonlinear phase shift by the sample is less than π. In addition, this approximation serves to estimate the sensitivity and monotonic interval for nonlinearity measurements more easily and thus helps us to maximize both the sensitivity and monotonic interval of measurements. We test this method with CS(2), a well-characterized third-order nonlinear refractive material using 21 ps laser pulses at 532 nm. We expect this method can be applied to high-order nonlinear refraction cases.
利用带有相位物体的非线性成像技术（NIT-PO），我们研究了各种样品的三阶非线性特性。在这项工作中，对于纯非线性折射材料，我们开发了一种近似方法来解析计算非线性折射系数。通过将穿过相位物体的物场分解为两个具有不同相位和光束半径的平顶光束，我们获得了近似相位对比度，从中提取非线性折射系数。当样品的轴上非线性相移小于π时，这种近似是有效的。此外，这种近似有助于更轻松地估计非线性测量的灵敏度和单调区间，从而帮助我们最大化测量的灵敏度和单调区间。我们使用532nm的21ps激光脉冲，以特性良好的三阶非线性折射材料二硫化碳（CS₂）对该方法进行了测试。我们期望这种方法能够应用于高阶非线性折射情况。
