Methods for uniform beam shaping and their effect on material ablation

Abstract

Phase-only beam shaping with a spatial light modulator (SLM) is a powerful tool in laser materials processing. It enables adapting the shaped profile to the ablation geometry and thereby tailoring the energy deposition. To mitigate speckle noise in tailored beam profiles, methods for uniform beam shaping were proposed. The two main approaches either implement averaging of speckled profiles or directly yield a uniform profile, i.e. by amplitude and wave front shaping. Even though both approaches provide comparable results in optical homogeneity, the ablation process differs. Even though it is important to know which method should be used for practical applications, a direct comparison of those two methods has not been studied before to the best of our knowledge. By employing both techniques in one setup, we perform ablation experiments on amorphous metal and investigate the results with respect to quality, efficiency, and feasibility. Averaging is especially suitable for ablating large areas with focus on homogeneity and simplicity. Amplitude and wave front shaping enables finer contours and sharper edges besides the obvious advantage of a uniform profile for single shot applications. Additionally, it exhibits no 0 th order of non-diffracted light. These features arise from the inherently more sophisticated and complex experimental setup.