Nanostructuring of solid surfaces by femtosecond laser pulses

Abstract. One-dimensional quasi-periodic structures whose period is much smaller than the wavelength o f exciting optical radiation have been obtained on a titanium surface under the m ulti-shot action o f linearly polarized femtosecond laser radiation at various surface energy densities. A s the radiation energy density increases, the one-dimensional surface nanogratings oriented perpendicularly to the radiation polarization evolve from quasi-periodic ablative nano grooves to regular lattices with sub-wavelength periods (90-400 nm). In contrast to the preceding works for various metals, the period o f lattices for titanium decreases with increasing energy density. The formation o f the indicated surface nanostructures is explained by the interference o f the electric fields o f incident laser radiation and a surface electromagnetic wave excited by this radiation, as shown by our transient reflectivity measurements and modeling, because the length o f the surface electromagnetic wave for titanium with significant interband absorption decreases versus increasing electron excitation o f the material