Femtosecond laser-induced periodic surface structures

The formation of laser-induced periodic surface structures (LIPSS) in different materials (metals, semiconductors, and dielectrics) upon irradiation with linearly polarized fs-laser pulses (tau similar to 30-150 fs, lambda similar to 800 nm) in air environment is studied experimentally and theoretically. In metals, predominantly low-spatial-frequency-LIPSS with periods close to the laser wavelength lambda are observed perpendicular to the polarization. Under specific irradiation conditions, high-spatial-frequency-LIPSS with sub-100-nm spatial periods (similar to lambda/10) can be generated. For semiconductors, the impact of transient changes of the optical properties to the LIPSS periods is analyzed theoretically and experimentally. In dielectrics, the importance of transient excitation stages in the LIPSS formation is demonstrated experimentally using (multiple) double-fs-laser-pulse irradiation sequences. A characteristic decrease of the LIPSS periods is observed for double-pulse delays of less than 2 ps. (C) 2012 Laser Institute of America.