Ultrafast thermal dynamics of nano-ripples formation via laser double pulses excitation

• The ultrafast thermal dynamics is proposed for explaining nano-ripples formation.
• The interplay of the electron diffusion and electron–phonon coupling are responsible for regulating nano-ripples formation.
• The pulse-to-pulse relevance coupling into target material can explain nano-ripples contrast modulation.

The ultrafast thermal dynamics of nano-ripples formation on gold film via ultrafast laser double pulses excitation is theoretically investigated by numerical simulations. The non-equilibrium thermal modulations with respect to the electron and phonon energy transfers within gold film is proposed for predicting the nano-ripples formation. It is revealed that the nano-ripples contrast on gold film surface can be well controlled via tuning the pulse energy ratio, pulse separation and pulse exchange of ultrafast laser double-pulse. It is attributed to the tunable energy transfer routes between the electron thermal diffusion and the electron–phonon coupling via tuning double pulses parameters. The study provides theoretical basis for producing high-contrast ripples for a wide range application in the fields such as high-absorptive solar cells, surface friction devices and super-hydrophobic surface.