Single pulse Nd:YAG laser irradiation of titanium: influence of laser intensity on surface morphology

The interaction between single-pulse Nd:YAG (λ=1.064 μm) laser radiation and Ti target surfaces was studied by scanning electron microscopy and profilometry. The laser-assisted surface modification was analyzed and described as a function of incident laser pulse intensity. The evolution of the surface morphology was explained in terms of liquid phase material displacement, vaporization and plasma shielding. The laser intensities characteristic for the transition between these surface processes were studied for the particular laser-target system. The development of wave-like surface topography was accounted by non-linear hydrodynamic instabilities evolving on the molten target surface. The material transport and its accumulation at the border of the imprints was assigned mainly to the effect of ambient gas breakdown and vaporization plasma recoil pressure. At high laser intensities the surface morphology was influenced by the plasma shielding.