On the formation of regular sub-wavelength ripples by femtosecond laser pulses on silicon

An experimental investigation on regular sub-wavelength laser induced periodic surface structures (LIPSS) by femtosecond laser pulses on silicon was carried out. In particular, the study reported in this paper indicates that the application of a 780-nm-wavelength femtosecond laser through a 0.2 mm pinhole aperture can produce LIPPS with spatial period of 710 nm. The use of AFM (atomic force microscopy) and of SEM (scanning electron microscope) provided the ability to study the mechanism for LIPPS formation. The study indicates that phase explosion plays an important role in mass removal during LIPPS formation.