Double- and Multi-Femtosecond Pulses Produced by Birefringent Crystals for the Generation of 2D Laser-Induced Structures on a Stainless Steel Surface, F. Fraggelakis, G. Giannuzzi, C. Gaudiuso, I. Manek-Hönninger, G. Mincuzzi, A. Ancona, R. Kling