Femtosecond laser induced surface nanostructures on copper

This study demonstrated circular surface nanostructures and femtosecond laser-induced periodic surface structures (FLIPSS) for copper produced by a Ti:Sapphire femtosecond laser beam of wavelength 800 nm and duration 120 fs. The circular textured nanostrucres could be created by a single laser pulse. The nanostructures in the center of the heated spot diminish as laser fluence increases and a crater is eventually made at higher fluences. The FLIPSS could only be generated by multiple laser pulses. The resulting periodic ripple-like nanostructures are in a line pattern, and their orientations are perpendicular to the polarization direction. A set of thermal models were also proposed to simulate thermal ablation for copper films, including a two-temperature model, phase change models for melting and evaporation, and phase explosion model. The predicted ablation depths are in good agreement with the existing experimental data.