Femtosecond Pulse Tailoring For Nanoscale Laser Processing Of Wide-Bandgap Materials: Temporal Asymmetric Pulses Versus Frequency Sweeps

Lars Englert, Matthias Wollenhaupt, Dirk Otto, Cristian Sarpe-Tudoran, Alexander Horn, Thomas Baumert, Claude Phipps
Control of two basic ionization processes in dielectrics i.e. photo ionization and electron-electron impact ionization on intrinsic time and intensity scales is investigated experimentally. In our experiment, we use a modified microscope set up to irradiate the surface of a fused silica sample with a single shaped pulse resulting in nanoscale ablation structures. The topology of the laser generated structures is measured by Atomic Force Microscopy (AFM). Structure parameters are investigated as
more » ... are investigated as a function of the pulse energy and the modulation parameters. We find different thresholds for surface material modification with respect to an asymmetric temporal pulse and its time reversed counterpart both showing a constant instantaneous frequency. However, we do not observe pronounced differences between up-and down-chirped radiation (i.e. symmetric temporal pulse envelope but asymmetric instantaneous frequency) in the measured structure diameters and thresholds.
doi:10.1063/1.3507114 fatcat:v7ghndwk2rgghdpfnfibsqavnu