Surface and bulk structuring of materials by ripples with long and short laser pulses: Recent advances

Ripples are formed on the surface of solid materials after interaction with laser pulses of high intensity/irradiance. When ultra-short sub-1 ps laser pulses are used, the observed morphology of ripples on surfaces becomes much more complex as compared with ripples formed by long laser pulses. Uniquely for the short laser pulses, ripples can be formed in the bulk. A better understanding of the fundamentals of light-matter interaction in ripples formation is strongly required. Experimentally observed ripples and dependence of their parameters on laser fabrication conditions and material properties are summarized first. Then, a critical review of relevant ripple formation mechanisms is presented, discussed, and formation conjectures are presented.

It is shown that formation of plasma at sub-critical or critical densities (i.e., solid state or breakdown plasmas) on the surface and in the bulk specific to the high-intensity ultra-short laser pulses has to be considered to account for the experimental observations. Surface and bulk ripples formed on/in dielectrics can be explained by the same model where electron–hole (solid state) plasma is formed at the very threshold of ripples formation. Ripple patterns have a strong application potential from sensing to light harvesting and (photo)catalysis mainly due to nanoscale features and self-replication of pattern over large macroscopic areas. Several emerging applications are shown.