Effect of using reflective target materials on enhancing UV nanosecond laser machining of sapphire

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The machining of sapphire, a hard and transparent material, is of significant interest in various industries due to its exceptional properties. Traditional machining methods for sapphire suffer from drawbacks such as low efficiency and poor processing quality. Laser machining, particularly using ultraviolet (UV) nanosecond lasers, has emerged as a promising alternative for machining sapphire. In this article, we explored the use of reflective target materials to enhance laser energy absorption during the machining of sapphire. The effect of different reflective target materials, including aluminum and silicon, on the laser machining process was examined. Parametric calculations and finite-difference time-domain (FDTD) simulation were performed to evaluate the laser intensity at the top surface of sapphire when a reflective target material was employed. The results demonstrated that the use of reflective target materials leads to increased laser intensity due to the interference of incident and reflected laser beams, thus improving material removal efficiency. Moreover, experimental observations confirmed the effectiveness of using reflective target materials in enhancing the machined depth of sapphire. For example, the machined depth of 21.6 µm with a power density of 1.7 × 108 W/cm2 increased to 23.3 µm and 26.5 µm by using silicon and aluminum target materials. It is found that using aluminum target led to higher machined depth than silicon owing to its higher reflectivity.