The optical nonlinearities of ZnO nanoparticles and ZnO crystal

Abstract

Based on Z-scan technique, the nonlinear absorption characteristics and nonlinear refraction characteristics of ZnO nanoparticles and ZnO crystal have been studied under the nanosecond (ns) laser pulses and the picosecond (ps) laser pulses respectively. The experimental results show that the nonlinear absorption characteristics of the ZnO nanoparticles and ZnO crystal are reverse saturable absorption mainly due to two-photon absorption under the ns laser pulses. ZnO nanoparticles don’t have nonlinear absorption, and the nonlinear absorption of the ZnO crystal is reverse saturable absorption under the ps laser pulses. The nonlinear refraction characteristics of ZnO nanoparticles are self-focusing under the ns and ps laser pulses respectively, and the nonlinear refractive indexs are 2.14×10-11 esu, 4.79×10-13 esu respectively because of bound electron. The nonlinear refraction characteristics of ZnO crystal are self-defocusing under the ns and ps laser pulses respectively, and the nonlinear refractive indexs are -2.2×10-8 esu, -2.91×10-11 esu respectively because of free carrier. The experimental results show that ZnO materials can influence the optical nonlinear characteristics, and laser pulse width has little influence on the optical nonlinear characteristics.