高功率绿光飞秒激光诱导产生钛表面周期性微结构

The femtosecond laser, which induces periodic microstructures on the surfaces of metallic materials, is extensively applied in photovoltaic power generation, self-cleaning, and biomedical fields. In this paper, we fabricate periodic microstructures on the surface of Ti by utilizing a green femtosecond laser with a power of 75 W, a pulse width of 800 fs, and a wavelength of 515 nm. First, the ablation threshold of Ti under the line-scan condition is discussed herein. The Ti surface microstructures are induced based on a 90° cross-surface scan processing. We derive the formula for the calculation of the effective-pulse number per unit point in the surface scanning and summarize the microstructural evolution. The results obtained demonstrate the following: 1) the ablation threshold of Ti by utilizing the green femtosecond laser is significantly lower than that of the previously reported long-wavelength infrared laser; 2) the surface microstructure of Ti can be attributed to the effective-pulse number per unit point and the laser fluence in the surface scanning. Due to the increase in the effective-pulse number, the microstructure changes from nonuniform distribution of hump to uniform columnar array structure when the laser fluence is low, or to interconnected hilly structure when the laser fluence is high. The similar structure can be obtained either by applying a high laser fluence and small effective-pulse number, or a low laser fluence and large effective-pulse number. The former can significantly increase processing efficiency.