Investigation on the material removal behavior of single crystal diamond by infrared nanosecond pulsed laser ablation

In this paper, the material removal behavior of the single crystal diamond (SCD) in the multi-passes infrared nanosecond pulse laser ablation is investigated, focusing on the formation mechanism of the surface cracks, the periodic ripples, the graphitization and the shape evolution of the groove. The simulation of the temperature field in the SCD pulse laser ablation process is firstly performed to show the possibly achieved peak temperature which is closely related to the material removal mechanism, and the experimental results indicate that the diamond materials are mainly removed by gasification, oxidation, delamination and fragmentation. The typical surface characteristic of the ablated SCD is dependent on the pulse duration, where graphitization, cracking and chipping appeared as the main form at the pulse duration of 8 ns, 50 ns, and 120 ns, respectively. In addition, the periodic ripples of 500-1100 nm on the side walls of the machined groove were induced when the laser energy density is lower than 40 J/cm(2). The obtained critical values of the laser fluence is of great significance for the optimization of the laser parameters in the surface microstructuring of SCD. On the whole, five characterized areas in the multi-passes infrared nanosecond pulse laser ablation surface are identified in the machined grooves, including the bottom smooth area, the side wall ripples area, the side wall non-ripples area, the edge transition area and the deposited metamorphic area due to the condensation of deposited carbon atoms and clusters, the formation mechanism of which, mainly including the thermal stress and the interaction between the laser pulse and the material, are discussed.