Controllable fabrication of super-resolution nanocrater arrays by laser direct writing

A super-resolution fabrication technique for highly-ordered nanocrater arrays is reported based on laser direct writing method. Nanocraters with diameters up to 40 nm, which is much smaller than the diffraction limit of laser system, are fabricated on titanium films using a 532 nm laser. The diameters of the craters are tunable from 350 nm to 40 nm, with a rigorous linear relationship versus the writing laser powers and an approximate linear relationship versus pulse widths. Laser ablation and oxidation are involved in formation mechanism and Gaussian distribution of laser energy density is proposed to play a key role of super-resolution structures.