Time-Dependent Detection of the Refractive Index Distribution of Nonlinear Optical Materials

The refractive index distribution (RID) measurement reveals detailed RI information and flaws on the sample. The time-dependent detection of the light- and thermal-induced RI change process of nonlinear optical materials was quantitatively studied by the scanning focused refractive index microscopy (SFRIM). The light- and thermal-induced RI change can be distinguished by means of curve fitting. Our method is compared with the traditional Z-scan technique, which can only measure the mean RI change across the sample. The experimental results show that the time-dependent detection of RID by SFRIM can provide a new point of view toward the investigation of nonlinear optical materials.