Drilling with ultrashort laser pulses at high repetition rates

Ultrashort laser pulses offer extraordinary precision in microprocessing a variety of materials, especially metals. Thermal and mechanical damage can be minimized by working at fluences not too far above the ablation threshold. However, this comes at the expense of low ablation rates and thus high processing times. A scaling of processing speed by increasing the fluence results in degradation in quality. Therefore, in this chapter we investigate the potential for scaling the processing speed by increasing the pulse repetition rate to several 100 kHz up to the MHz regime with average laser powers of up to 100 W exemplary for percussion drilling of metals. Limiting factors like particle shielding and heat accumulation are identified, their dependence on laser parameters as well as material properties are discussed and options for drilling at significantly improved speeds are highlighted.