Keywords: 
• 非线性光学 /
• 非线性光谱学

Abstract: This article presents a brief introduction to the birth and early investigations of nonlinear op- tics, such as second harmonic generation, sum and difference frequency generation, stimulated Raman scat-tering, and self-action of light etc. Several important research achievements and applications of nonlinear optics are presented as well, including nonlinear optical spectroscopy, phase conjugation and adaptive op- tics, coherent nonlinear optics, and high-order harmonic generation. In the end, current and future research topics in nonlinear optics are summarized.