Theoretical and Experimental Investigation of the Formation of High Spatial Frequency Periodic Structures on Metal Surfaces Irradiated by Ultrashort Laser Pulses

Experimental results on the formation of small-scale periodic nanostructures during ablation of solids by pico- and femtosecond laser pulses are presented. The period of these nanostructures is in the range of 50 to 100 nm, and they may coexist with known periodic nanostructures, whose period and orientation is determined by the laser wavelength and amounts to several hundreds of nanometers. The formation of high-frequency periodic structures with a period of about 100nm is theoretically analyzed by joint numerical solution of the heat conduction problem and Navier?Stokes equation. It is shown that their orientation is determined by the melt bath geometry.