Effect of Surface Structural Modifications on Absorptivity of Platinum in Multi-Pulse Femtosecond Laser Ablation

Change in absorptivity of platinum caused by surface modifications in multi-pulse femtosecond laser ablation is studied as a function of the number of applied laser pulses at various values of laser fluence and ambient gas pressure. We show that laser-induced surface modifications enhance significantly the absorptivity due to nano-, micro-, macro-structures produced by ablation. At a sufficiently high fluence and large number of applied pulses the absorptance of ablated platinum surface can reach a value close to 100%. The absorptivity enhancement caused by surface structural modifications produced by ablation in vacuum is greater then that in air