High-quality high-throughput silicon laser milling using a 1 kW sub-picosecond laser

We report on high-quality high-throughput laser milling of silicon with a sub-ps laser delivering more than 1 kW of average laser power on the workpiece. In order to avoid heat accumulation effects, the processing strategy for high-quality laser milling was adapted to the available average power by using five-pulse bursts, a large beam diameter of 372 µm to limit the peak fluence per pulse to approximately 0.7J/cm², and a high feed rate of 24 m/s. As a result, smooth surfaces with a low roughness of S_a≤0.6µm were achieved up to the investigated milling depth of 313 µm while maintaining a high material removal rate of 230mm³/min.