Optical nonlinearity investigation of Bi₂Te₃

To realize 2-D material nonlinear optical applications, including wavelength generation, ultrafast optical processing, and saturable absorber for ultrafast laser, the information of optical nonlinearity property for given material is very important. In this work, ultra-low peak intensity (10³ to 10⁵ W/cm²) z-scan measurement was proposed and buildup for studying the discontinuity of conventional nonlinear transmission with low and high pulse energy. The two photon absorption behavior was observed and is with tremendous large coefficient of 2.03x10^-2 cm/W for excitation power of 100uW. This can be used to interpret and resolve the discontinuity.