Nonlinear Absorption Properties of Quantum Dots of CdTe / ZnS and CdTe / CdS

Abstract

Herein, the nonlinear absorption properties of CdTe / ZnS and CdTe / CdS were investigated. The nonlinear absorption characteristics of these two kinds of quantum dots (QDs) were measured by Z-scan experimental apparatus under the wavelength of 532 nm, pulse widths of 4 ns and 21 ps, respectively, and a repetition frequency of 10 Hz. The results of experiment indicate the nonlinear absorption of CdTe / ZnS QDs and CdTe / CdS QDs show saturation absorption in nanosecond and picosecond laser pulses. By theoretical data fitting, we can draw a conclusion that the nonlinear absorption coefficients of CdTe / ZnS QDs and CdTe / CdS QDs are -2.57 × 10-10 m / W and -2.08 × 10-10 m / W,respectively;at a pulse width of 21 ps, the nonlinear absorption coefficients of CdTe / ZnS QDs and CdTe / CdS QDs are -1.38 × 10-11 m / W and -1.14 × 10-11 m / W,respectively. From the final data analysis, it can be seen that the nonlinear absorption properties of CdTe / ZnS QDs and CdTe / CdS QDs in the effect of nanosecond laser pulses are stronger than those under the condition of picosecond laser pulses. At the same time, it was found that under the different laser pulses of nanosecond and picosecond, CdTe / ZnS QDs showed stronger nonlinear absorption than that of CdTe / CdS QDs.