Dynamics of ripple formation on silicon surfaces by ultrashort laser pulses in subablation conditions

An investigation of ultrashort pulsed laser induced surface modification due\nto conditions that result in a superheated melted liquid layer and material\nevaporation are considered. To describe the surface modification occurring\nafter cooling and resolidification of the melted layer and understand the\nunderlying physical fundamental mechanisms, a unified model is presented to\naccount for crater and subwavelength ripple formation based on a synergy of\nelectron excitation and capillary waves solidification. The proposed\ntheoretical framework aims to address the laser-material interaction in\nsub-ablation conditions and thus minimal mass removal in combination with a\nhydrodynamics-based scenario of the crater creation and ripple formation\nfollowing surface irradiation with single and multiple pulses, respectively.\nThe development of the periodic structures is attributed to the interference of\nthe incident wave with a surface plasmon wave. Details of the surface\nmorphology attained are elaborated as a function of the imposed conditions and\nresults are tested against experimental data.\n