Deep hole drilling in metals by femtosecond laser pulses

The advantages of ultrashort laser pulses for high quality micromachining have been early recognized. In this work we have used high energy femtosecond pulses to explore the drilling efficiency in metals up to very high laser intensities. The experiments have been carried out at the CEA femtosecond laser facility at Saclay. The Ti-Sa laser that was used for the present work is delivering up to 10 mJ per pulse at 800 nm, with a repetition rate of 1 KHz. The pulse duration is 35 fs. The beam diameter at the sample is about of 20 mum, leading to maximum fluences of 600 J/cm². We have systematically measured the drilling efficiency for different types of metals (Tantalum, Molybdenum, and one SMA (shape shape memory alloy), with thicknesses in the range 200 mum to 4 mm.