Email addresses: maragkaki@lat.rub.de (Stella Maragkaki),The physical mechanisms of the laser-induced periodic surface structures (LIPSS) formation are studied in this paper for single-pulse irradiation regimes. The change in the LIPSS period with wavelength of incident laser radiation is investigated experimentally, using a picosecond laser system, which provides 7-ps pulses in near-IR, visible, and UV spectral ranges. The experimental results are compared with predictions made under the assumption that the surface-scattered waves are involved in the LIPSS formation. Considerable disagreement suggests that hydrodynamic mechanisms can be responsible for the observed pattern periodicity.

This paper presents a novel one-step method for the periodical nanopatterning and reduction of graphene oxide (GO). Self-organized periodic structures of reduced graphene oxide (rGO) appear on GO surfaces upon processing with a femtosecond laser at fluences slightly higher than the fluence needed for reduction of the GO. This indicates that the periodic pattern is formed either simultaneously with or due to the reduction of the GO. The laser-induced reduction of GO was identified by sheet resistance measurements, Raman and X-ray photoelectron spectroscopy. This fast and simple method to both reduce and periodically structure GO offers a variety of possible applications in printed and flexible electronics.

In this paper we analyze femtosecond laser processing of metals in liquids searching for optimal conditions for predictable ablation. Incident laser pulses are stretched or compressed, self-focused and scattered on bubbles and on surface waves in the liquid environment. Influence of these effects on the laser intensity distribution on the target surface is discussed and optimal processing parameters are suggested.