Fundamental Study of Ablation Mechanisms in Crystalline Silicon and Gold by Femtosecond Laser Pulses: Classical Approach of Two Temperature Model
Ultra-short laser material processing has received much attention due to the broad applications across nearly all manufacturing sectors. Ultra-short laser ablation is a complex phenomenon involving laser energy spatial distribution, energy absorption on the irradiated surface, transient changes in optical response, and ablation. In order to determine the ablation characteristics and performance, a fundamental study of the interaction between ultra-short laser pulses and the material will be valuable. A theoretical analysis of ultra-short laser-matter interaction can be represented by the two-temperature model which describes the temperature of the electron or carrier and lattice in non-equilibrium conditions when ultra-short laser pulses are applied. During ultrafast irradiation, due to peculiarities between the metal energy absorption to in contrast to semiconductor, a comparative study of silicon and gold ablation mechanism presented. A 2D axial symmetry simulated ablation profiles were compared with the experimental result at fluence ranging from 1 J/cm2 to 9 J/cm2 at the wavelength of 515 nm and 180 fs laser on the silicon and gold sample. The concordance between model calculations and experimental data demonstrates that fs laser ablation of silicon is thermal in nature in a low fluence regime, whereas it is non-thermal in a high-fluence regime. On the other hand, the phase explosion mechanism is prevalent to understand the ablation characteristics of gold with fs pulses. Fundamental information such as the time evolution of the carrier density in silicon, carrier or electron temperature evolution, and lattice temperature evolution can be obtained from the simulation results.