针对近红外(800 nm)及其二倍频(400 nm)飞秒激光脉冲在金属钼表面诱导产生周期性条纹结构的情况进行了研究，分析比较了入射激光能量、脉冲重叠数、激光中心波长和加工氛围等实验参数对金属表面自组织形成的条纹结构空间周期的影响，并利用中心波长为400 nm 的飞秒激光在水环境中于单晶钼表面制备出了空间周期仅约160 nm 的条纹结构。同时针对水中加工的情况,在理论上提出了入射激光与表面等离子体波发生干涉和表面等离子体波形成驻波两种机制相互竞争的物理模型，很好地解释了实验现象，对于深入理解飞秒激光在金属表面进行纳米尺度的加工制备具有重要意义。

The formation of laser induced periodic surface structure (LIPSS) on the surface of molybdenum is investigated by using 400 nm and 800 nm femtosecond lasers. In the experiment, the influences of the processing parameters, specifically pulse energy, central wavelength, pulse overlap number and the fabricating ambient on the spatial period of the LIPSS are examined. In the ambient of water, ripple-like LIPSS on molybdenum with subwavelength spatial period of only around 160 nm is fabricated successfully by using 400 nm femtosecond laser with optimized processing parameters. Besides, an improved model is proposed to account for the LIPSS formation in the water. In this model, two kinds of interference mechanism, including the interference between the incident laser and the excited surface plasmon polaritions, and the other between surface plasmon polaritions propagating opposite directions, which causes standing wave, compete with each other. The improved model agrees well with the experimental phenomena, which is of great significance for fabricating nano-structure on the surface of metals.