The preparation of the wavelength-scale micropores on metallic surfaces is limited by the high opacity of metal. At present, most micropores reported in the literature are more than 20 µm in diameter, which is not only large in size, but renders them inefficient for processing so that it is difficult to meet the needs of some special fields, such as aerospace, biotechnology, and so on. In this paper, the rapid laser fabrications of the wavelength-scale micropores on various metallic surfaces are achieved through femtosecond MHz burst Bessel beam ablation. Taking advantage of the long-depth focal field of the Bessel beam, high-density micropores with a diameter of 1.3 µm and a depth of 10.5 µm are prepared on metal by MHz burst accumulation; in addition, the rapid fabrication of 2000 micropores can be achieved in 1 s. The guidelines and experimental results illustrate that the formations of the wavelength-scale porous structures are the result of the co-action of the laser-induced periodic surface structure (LIPSS) effect and Bessel beam interference. Porous metal can be used to store lubricant and form a lubricating layer on the metallic surface, thus endowing the metal resistance to various liquids' adhesion. The microporous formation process on metal provides a new physical insight for the rapid preparation of wavelength-scale metallic micropores, and promotes the application of porous metal in the fields of catalysis, gas adsorption, structural templates, and bio-transportation fields.
Keywords: MHz burst Bessel beam; femtosecond laser; laser-induced periodic surface structure (LIPSS); porous metal; wavelength-scale micropores.