The influence of processing environment on laser-induced periodic surface structures generated with green nanosecond laser

Abstract

Laser-induced periodic surface structures (LIPSS) are nanometric surface undulations produced by short and ultrashort pulsed lasers. The production of high-quality LIPSS is essential to obtain the required surface responses in various applications. In this work, the LIPSS were fabricated on stainless steel surfaces by a 515 nm nanosecond laser operating under ambient and argon enriched atmospheres to investigate their quality. The LIPSS quality is correlated to the diffracted light intensity and their key geometric parameters such as periodicity and amplitude. The LIPSS formation was observed at an accumulated fluence of above 13.9 J/cm2 and the optimal processing window was sustained up to 46.2 J/cm2 before the oxidation occurred. The LIPSS generated in the argon environment exhibited a relatively higher intensity of the diffracted light than those processed in the ambient conditions. Furthermore, LIPSS generated in argon showed minimum surface defects and higher amplitude ripples compared to those in air. The X-ray photoelectron spectroscopy analysis revealed that the ratio of oxygen to metal species decreased in the argon atmosphere and thus minimal surface oxidation occurred on the samples. Since the generation of high-quality LIPSS is a prerequisite for an accurate predictive modeling of surface responses, the results reported here show that good nanostructured surfaces can be produced with cost-effective nanosecond green lasers.