Extraordinary enhanced absorptivity of gold surface ablated with femtosecond laser pulses

In this work, we study absorptivity enhancement due to surface structural modification induced by multi-pulse femtosecond laser ablation of a bulk gold sample. It is shown that absorptivity enhancement in multi-pulse ablation is caused by a combination of nano-, micro-, and macro-structural surface modifications. Femtosecond laser-induced surface nanostructuring is found to be a significant factor enhancing the absorptivity. This absorptivity enhancement of the nano-structured surface is explained as a result of both light scattering from produced ramified gold surface and resonant linear and nonlinear light absorption by coupled nanostructures (spheres, wires, cones).