Picosecond laser drilling grids in aluminium foil at 532 and 355 nm wavelengths

Abstract

Ultra-short laser drilling technique enables production of filters, membranes, microfluidic, photonic, and biomedical devices. Micro-hole grids were drilled in aluminum foil using a 28 picosecond Nd:YAG laser operated at wavelength of 532 and 355 nm with energy up to 18 and 12 mJ, respectively. Varying pulse energy and number, micro-holes obtained at 355 nm and 3.6-9 mJ had the appropriate mean diameter of 36-86 μm. However, the circularity changed in 0.5-0.94. For the 2nd harmonic the mean diameter varied 15-61 μm at 0.36-9 mJ with the circularity of 0.81-0.92. The morphology of the area surrounding micro-holes investigated by scanning electron microscopy exhibited distribution of droplets dominated size 0.9-10 μm , which is feasible for filtration of contaminated liquids. Local elemental composition of the area determined by energy dispersive spectroscopy discovered significant increase in the concentration of C and O, and also emergency of F, depending on laser fluence under vapor-dominated ablation mode, where nuclear reactions are excited in hot plasma.