Finite element simulation study on ultraviolet nanosecond laser machining of microgrooves in diamond (<italic>invited</italic>)

ObjectiveDiamond is widely used in high-end industrial applications due to its exceptional hardness and thermal properties. However, its extreme mechanical properties also make it difficult to machine, especially when fabricating microstructures with high precision and minimal defects. This study aims to investigate the formation mechanisms and morphological evolution of diamond microgrooves under UV nanosecond laser processing via finite element simulation. The primary objectives include analyzing the effects of key laser parameters—such as power, scanning speed, and scanning times—on microgroove geometry, identifying the root causes of common defects like asymmetry, and proposing an optimized scanning strategy to improve machining quality.MethodsA three-dimensional finite element model was established using COMSOL Multiphysics, integrating solid heat transfer and deformed geometry modules to simulate the laser-material interaction process. A Gaussian-distributed moving heat source was employed to represent the UV nanosecond laser beam. To account for energy loss due to plasma shielding and debris ejection in actual processing, an energy shielding factor (η) was introduced. The model simulated the temperature field variation and material removal behavior under different laser parameters and scanning paths. Simulations were performed with varied laser powers (5-10 W), scanning speeds (300-900 mm/s), and multiple scanning passes to systematically study their influence on microgroove depth, width, and cross-sectional morphology.Results and DiscussionsThe simulation results revealed that laser power and scanning speed significantly affect microgroove depth, while the effect on microgroove width was relatively minor. Increasing laser power led to greater depth, though the rate of increase slowed at higher power levels (10 W). Higher scanning speeds resulted in reduced depth due to decreased overlap of laser spots. As the scanning times increased, microgroove depth grew almost linearly until saturation occurred, accompanied by the formation of a V-shaped bottom profile. Cross-sectional and longitudinal analyses indicated that asymmetric sidewalls and bottom inclination were caused by non-uniform energy deposition and preheating effects induced by sequential scanning. Temperature distribution analysis demonstrated that regions scanned later experienced higher initial temperatures, leading to increased material removal rates and resulting in geometric inaccuracies.ConclusionsThis study successfully established a finite element model to simulate the UV nanosecond laser machining process of diamond microgrooves, providing deep insights into the influence of processing parameters on groove morphology. It was found that asymmetric defects arise mainly from localized temperature differences and uneven energy distribution caused by unidirectional scanning paths. To address these issues, it is suggested to use a scanning path with temperature compensation during microgroove machining (e.g., S-shaped path), which can balance the preheating effect and reduce geometric inaccuracies. These findings offer a theoretical foundation and practical guidance for optimizing laser processing parameters and scanning strategies to achieve high-quality, precision diamond microstructures.