Ablation Depth And Mechanism Of Special Metals Irradiated By Femtosecond Laser

Femtosecond laser shows advantages in the field of micromachining because it can reach the highest power in the shortest time.Ni Ti shape memory alloy and CuZr amorphous alloy are widely used for their unique properties. Femtosecond laser interaction with special metals process is complicated. The mechanism is different for different laser energy and materials. Further studying and exploring the ablation depth and mechanism of femtosecond laser ablating the NiTi shape memory alloy and CuZr amorphous alloy are particularly important for reducing the ablation damage of materials, enhancing the ability of laser processing materials, and implementing to optimize the processing technology systemically.In the paper, the process of femtosecond laser ablating special metals is simulated by combing the two-temperature model with molecular dynamics method. The main works aimed at the study are as follows:(1) The effects of femtosecond laser fluence on the ablation depth is simulated during the interaction of femtosecond laser with NiTi shape memory alloy. In the simulation the NiTi shape memory alloy film with the depth of 90 nm is irradiated by the single pulse with the duration of100 fs and the fluences varying from 0 to 125 mJ/cm2. The simulation results show that two different ablation phases exist for single pulse ablating Ni Ti shape memory alloy. For lower fluence the ablating result presents gentle ablation phase, the ablation depth is lower and related with the optical penetration depth. For higher fluence the ablating result presents strong ablation phase and the ablation depth increases markedly.(2) Predicting the morphology of Ni Ti target irradiated by the single pulse via “mosaic approach” shows that more flat ablation craters at the bottom can be obtained by using femtosecond laser fluence near the ablation threshold to irradiate the target.(3) The effects of femtosecond laser fluence on the time of electroacoustic coupling is simulated during the interaction of femtosecond laser with CuZr amorphous alloy. The result shows that the time of electroacoustic coupling increase with increasing laser fluence.(4) The effects of femtosecond laser fluence with a typical pulse width on the ablation depth is simulated during the interaction of femtosecond laser with CuZr amorphous alloy. The simulation results show that the ablation threshold of CuZr amorphous alloy is around 40mJ/cm2. When the fluence exceeds 80 mJ/cm2, the ablating result present strong ablation phases. In addition, because of the initial disordered structure, amorphous alloy do not need absorb energy to destroy its crystal structure before being ablated so that the lower fluence can lead tostrong ablation phases.