The influence of ultra-fast temporal energy regulation on the morphology of Si surfaces through femtosecond double pulse laser irradiation

摘要

The effect of ultra-short laser-induced morpho­logical changes upon irradiation of silicon with double pulse sequences is investigated under conditions that lead to mass removal. The temporal delay between 12 double and equal-energy pulses (E_p = 0.24 J/cm~2 each, with pulse duration t_p = 430 fs, 800 nm laser wavelength) was varied between 0 and 14 ps and a decrease of the damaged area, crater depth size and periodicity of the induced subwavelength ripples (by 3-4 %) was observed with increasing pulse delay. The proposed underlying mechanism is based on the combina­tion of carrier excitation and energy thermalization and cap­illary wave solidification and aims to provide an alternative explanation of the control of ripple periodicity by tempo­ral pulse tailoring. This work demonstrates the potential of pulse shaping technology to improve ultra-fast laser-assisted microanoprocessing.