The thermal stress damage process of 1080 nm laser ablation of single crystal germanium was recorded in real time using a high-speed CCD. A three-dimensional finite element numerical model based on Fourier's heat conduction equation, Hooke's law and Alexander Hasson equation was developed to analyze the thermal stress damage mechanism involved. The damage morphology of the ablated samples was observed using an optical microscope. The results show that the cooling process has an important influence on the fracture in the laser irradiated region of single crystal germanium. The fracture is the result of a combination of thermal stress and local yield strength reduction.
.To compare the processing efficiency and quality of 20- to 1000-Hz pulsed laser and continuous laser ablating single-crystal germanium wafers, experiments and numerical simulations were performed. The experiments were conducted by varying the duty cycle and repetition frequency of a pulsed laser to ablate single-crystal germanium with the same total laser energy and irradiation time of 100 ms, and comparing the temperature-rise profile during ablation and the damage morphology after ablation. The temperature-rise curves during the ablation and the damage morphologies after the ablation were compared. Numerical simulations were performed to compute the dislocation field of single-crystal germanium ablated by laser with different parameters to compare the size of the heat-affected zone (HAZ) formed on the sample surface after the laser ablation with different parameters. The results show that the sample surface has the largest ablated pore size and the smallest HAZ after ablation at a laser repetition frequency of 20 Hz and a duty cycle of 5%; the smallest pore size and the largest HAZ after ablation at a laser repetition frequency of 1000 Hz and a duty cycle of 50%, and the continuous laser results are in the middle.
Numerical calculations and experimental approaches are used to examine the slip characteristics of 1064 nm laser ablated single crystal germanium. The ablation and cooling processes are used to investigate the influence of laser power density on the creation of the slip process. A 1064 nm continuous laser and a nanosecond laser were used to ablate single-crystal germanium samples, and the damage to the surface was seen using an optical microscope. The results demonstrate that raising the laser power density to 107 W/cm2 efficiently suppresses slip production during laser processing.
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