Influence of the temporal shape of femtosecond pulses on silicon micromachining

Abstract

The influence of femtosecond laser pulse shaping on silicon wafer micromachining is explored. Surface second harmonic generation provides in situ pulse characterization of the laser pulses, and plasma and atomic emissions were identified as valuable indicators of the micromachining process. The ablation threshold was found to decrease as the bandwidth of the pulses increases, as well as for shorter pulses. Dependence of atomic and plasma emissions on temporal shape of the pulses confirmed that emission preceded ablation and has a threshold as well. The morphology of micromachined holes was observed to be dependent upon pulse duration.