Ultrafast dynamics of material excitation of dielectrics with ultrashort pulsed Bessel beams

We report on the dynamics of the excitation process of dielectrics using a spatial Bessel beam intensity distribution with pulse durations below 10 ps. The generated free-electron plasma is analyzed by time-resolved transversal pump-probe shadowgraphy on a timescale up to 20 ps after initial excitation. Our measurements reveal the ultrafast generation of the free-electron plasma, which reaches a maximum after approximately 10 ps. The subsequent relaxation is comparable slow with a time constant in the range of 100 ps. We perform measurements with different pump pulse durations in the range from 0.1 ps up to 9 ps and observe that the spatial distribution of the generated free-electron plasma strongly depends on the pulse duration and pulse energy. Our results show that the spatial distribution of the free-electron plasma can be controlled by a coarse adjustment of the pulse parameters. The understanding of the correlation of the spatial energy deposition and pulse parameters is useful for a high precision and fast glass cutting process.