From ripples to spikes: A hydrodynamical mechanism to interpret femtosecond laser-induced self-assembled structures

Materials irradiated with multiple femtosecond laser pulses in subablation conditions are observed to develop various types of self-assembled morphologies that range from nanoripples to periodic microgrooves and quasiperiodic microspikes. Here, we present a physical scenario that couples electrodynamics, describing surface plasmon excitation, with hydrodynamics, describing Marangoni convection and counter-rolls, to elucidate this important subablation regime of light-matter interaction in which matter is being modified; however, the underlying process is not yet fully understood. The proposed physical mechanism could be generally applicable to practically any conductive material structured by ultrashort laser pulses; therefore it can be useful for the interpretation of further critical aspects of light-matter interaction.