Controlling LIPSS formation on Ni surface using near-infrared laser beam and its low-order harmonics

Ultrafast laser ablation of metal surfaces is a common physical process used to generate periodic surface structures with tuneable multifunctionality for various applications in science and technology. In this work, the formation of femtosecond laser-induced periodic surface structures (LIPSSs) is investigated with 50 kHz repetition rate laser of 40 fs pulse duration and a central wavelength (lambda(w) = 1030 nm) along with its second (lambda(w) = 515 nm) and third (lambda(w) = 343 nm) harmonic components. The variation in the LIPSS periodicity is demonstrated by changing the wavelength of the ablating laser pulses. LIPS S with periodicity similar to 0.85 mu m at the fundamental ablating pulses, similar to 0.42 mu m periodicity at the second harmonic, and similar to 0.35 mu m periodicity at the third harmonic were observed. The third harmonic radiation was generated in an air-filament with minimal temporal delay with respect to the fundamental driving pulses to structure Nickel surfaces at ambient conditions. The approach demonstrates the potential for generating very fine LIPSS on materials' surfaces using the efficient high-order harmonics of an infrared fundamental laser beam.