Highly Efficient Micro Structuring of Metals, Ceramics and Dielectrics with Nd:YAG and Excimer Lasers

Abstract

We performed experiments on micro structuring of metals and ceramics with solid state lasers and with an excimer laser. With several ns-Nd:YAG lasers we achieved high ablation rates and precise structures in Al203 (ceramic and sapphire), AIN, Ni-base alloy, platinum, tungsten and many more materials. With a master-oscillator power-amplifier (MOPA) system up to 125 W@1064 nm with a beam quality of M2=2.3 were achieved. Just to highlight two exemplary extremes: With the MOPA system high aspect ratio drilling was performed into sapphire (depth/diameter: 18 mm/100 pm) as well as 1024 micro holes (each 12 pm diameter) shot on an area of only 1 mm2. Due to the excellent beam quality of the Nd:YAG system combined with a CNC precision machine laser cutting of tungsten masks resulted in a resolution of but a few microns. These masks were used for subsequent excimer laser mask projection tasks. We performed precision micro structuring of fused silica (Si02) and CaF2 by laser-induced plasma-assisted ablation (LIPAA) with a conventional KrF excimer laser (248 nm). Mask projection of the UV light is realized onto the rear surface of the VUV window samples. The plasma generated from a metal target located behind the rear surface of the VUV window effectively assists in the ablation. In the case of fused silica, we obtain high-quality complex micro structures with structure depths even above 500 pm, corresponding to aspect ratios of 1:5 and better.