Nanostructuring with Femtosecond Laser Pulses on Patterned DLC Surface

We have studied the origin of nanostructuring on diamond-like carbon (DLC) film in femtosecond laser ablation. Using patterned targets including submicrometer-size stripe arrays on the surface, we found that the nanostructure starts to be formed along the direction perpendicular to the laser polarization on the crest of the stripe. The results obtained demonstrate that the nanometer-size ablation on the DLC surface is initiated and enhanced with a local field that is generated by the coherent production of free electrons in a surface area smaller than the laser wavelength.