Prepulse effects in short pulse laser machining

Summary form only given. The use of femtosecond lasers allows materials processing of practically any material with extremely high precision and minimal collateral damage. Advantages over conventional laser machining (using pulses longer than a few tens of picoseconds) are realized by depositing the laser energy into the electrons of the material on a time scale short compared to the transfer time of this energy to the bulk of the material, resulting in increased ablation efficiency and negligible shock or thermal stress. High average power, chirped-pulse amplification (CPA) systems required for short pulse materials processing typically use a regenerative amplifier. This component, in particular, can produce prepulses from leakage at each round trip as well as from spectral modulation. We examined the effect that prepulses can have on both drilling rates and hole quality for drilling holes in stainless steel, using a 1 kHz, 4 W Ti:sapphire CPA laser.