Simulation of femtosecond laser ablation of silicon

Femtosecond laser ablation is an important process in micromachining and nanomachining of microelectronic, optoelectronic, biophotonic and MEMS components. The process of laser ablation of silicon is being studied on an atomic level using molecular dynamics simulations. We investigate ablation thresholds for Gaussian laser pulses of 800 nm wavelength, in the range of a few hundred femtoseconds in duration. Absorption is modelled via linear and 2-photon absorption processes into a hot electron bath which then transfers energy into the crystal lattice. The simulation box is a narrow column approximately 5.4 nm x 5.4 nm x 81 nm with periodic boundaries in the x and y transverse directions and a 1-D heat flow model at the bottom coupled to a heat bath to simulate an infinite bulk medium corresponding to the solid bulk material. A modified Stillinger-Weber potential is used to model the silicon atoms. The calculated thresholds are compared to various reported experimental values for the ablation threshold of silicon. We provide an overview of the code and discuss the simulation techniques used.

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