Ad-hoc design of temporally shaped fs laser pulses based on plasma dynamics for deep ablation in fused silica
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We have analyzed the ablation depth yield of fused silica irradiated with shaped pulse trains with a separation of 500 fs and increasing or decreasing intensity envelopes. This temporal separation value is extracted from previous studies on ablation dynamics upon irradiation with transform-limited 100 fs laser pulses. The use of decreasing intensity pulse trains leads to a strong increase of the induced ablation depth when compared to the behavior, at the same pulse fluence, of intensity increasing pulse trains. In addition, we have studied the material response under stretched (500 fs, FWHM) and transform-limited (100 fs, FWHM) pulses, for which avalanche or multiphoton ionization respectively dominates the carrier generation process. The comparison of the corresponding evolution of the ablated depth vs. fluence suggests that the use of pulse trains with decreasing intensity at high fluences should lead to enhanced single exposure ablation depths, beyond the limits corresponding to MPI- or AI-alone dominated processes.
KeywordsShaped Pulse Pulse Train Carrier Generation Ablation Depth Multiphoton Ionization
This work has been partially supported by the Spanish TEC2008-01183 and TEC2011-22422 projects. J.H.-R. and D.P. acknowledges a grant of the Spanish Ministry of Science and Innovation. W.G. acknowledges the CSIC (I3P Program contracts co-funded by the European Social Fund). We are grateful to Professor S. Marcos from IO-CSIC for providing access to the optical interference microscope.
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