Self-organized micro/nano structures in metal surfaces by ultrafast laser irradiation

Ultrafast laser pulse interaction with matter, leading to formation of self-organized conical micro/nano structures in various metals like Ti, Al, Cu, and stainless steel have been observed. Influence of laser parameters such as fluence, number of shots, and gaseous environments on micro/nano structure formation have been investigated. The critical fluence required for well-developed structure formation is dependent on the optical and thermo-physical properties of the materials. By changing the number of laser shots to generate micro/nano structures, surface reflectance of Ti surface could be tailored from their original value (over 50%) to near zero over the wavelength range of 500–1000 nm. Also, we have demonstrated that arrays of micro/nano holes could be formed in thin Ti foils by direct laser treatment.