Experimental investigation and 3D-simulation of the ablated morphology of titanium surface using femtosecond laser pulses

The femtosecond laser ablated morphology on titanium surface is investigated theoretically and experimentally. A three dimensional two temperature model (3D-TTM) is used to simulate the surface morphology of titanium sample which is irradiated by femtosecond laser pulses. The electron heat capacity and electron-phonon coupling coefficient of titanium (transition metal) are complex temperature dependent, so the two parameters are corrected based on the theory of electron density of states (DOS). The model is solved by the finite difference time domain (FDTD) method. The 3D temperature field near the target surface is achieved. The radius and depth of the ablated crater are obtained based on the temperature field. The evolutions of the crate's radius and depth with laser fluence are discussed and compared with the experimental results. It is found that the back-flow of the molten material and the deposition of the material vapor should be responsible for the little discrepancy between the simulated and experimental results. The present work makes a better understanding of the thermodynamic process of femtosecond laser ablating metal and meanwhile provides an effective method tool to predict the micro manufacturing process on metals with femtosecond laser.