Vol. 42, Issue 4, pp. 795-803 (2012)

Abstract

Laser-induced periodic surface structures (LIPSS) (ripple) with different spatial frequencies have been observed after irradiation of stainless steel surfaces by femtosecond laser pulses in the air. Low spatial frequency LIPSS (LSFL) with the period (about 830 nm) close to the laser wavelength and high spatial frequency LIPSS (HSFL) with half wavelength (about 410 nm) were dependent on the scanning speed of laser focus. The sharp transition from the single LSFL to double HSFL structures occurs at 5 mm/s. This abrupt transition of dividing one ripple into two equals was proved.