Abstract
High-peak-power fs-laser filaments offer unique characteristics attractive to remote sensing via techniques such as remote laser-induced breakdown spectroscopy (R-LIBS). The dynamics of several ablation mechanisms following the interaction between a filament and a solid determines the emission strength and reproducibility of target plasma, which is of relevance for R-LIBS applications. We investigate the space- and time-resolved dynamics of ionic and atomic emission from copper as well as the surrounding atmosphere in order to understand limitations of fs-filament-ablation for standoff energy delivery. Furthermore, we probe the shock front produced from filament-target interaction using time-resolved shadowgraphy and infer laser-material coupling efficiencies for both single and multiple filament regimes through analysis of shock expansion with the Sedov model for point detonation. The results provide insight into plasma structure for the range of peak powers up to 30 times the critical power for filamentation Pcr. Despite the stochastic nucleation of multiple filaments at peak-powers greater than 16 Pcr, emission of ionic and neutral species increases with pump beam intensity, and short-lived nitrogen emission originating from the ambient is consistently observed. Ultimately, results suggest favorable scaling of emission intensity from target species on the laser pump energy, furthering the prospects for use of filament-solid interactions for remote sensing.
Highlights
High-peak-power fs-laser filaments offer unique characteristics attractive to remote sensing via techniques such as remote laser-induced breakdown spectroscopy (R-LIBS)
High-peak-power fs-laser pulses propagated in air are of significant interest for many applications such as remote sensing[1,2], remote laser-induced breakdown spectroscopy (R-LIBS)[3], artificial lighting[4], and others[5,6]
Noteworthy challenges in R-LIBS arise from intensity clamping in the filament core limited by multiphoton ionization (MPI) of air molecules[9], instabilities in directed energy delivery for greater peak powers which lead to stochastic formation of multiple filaments[9,22], and emission from atmospheric species from the filament and target plasmas[2,3,9,14], which contributes to background in optical emission spectroscopy
Summary
High-peak-power fs-laser filaments offer unique characteristics attractive to remote sensing via techniques such as remote laser-induced breakdown spectroscopy (R-LIBS). High-peak-power fs-laser pulses propagated in air are of significant interest for many applications such as remote sensing[1,2], remote laser-induced breakdown spectroscopy (R-LIBS)[3], artificial lighting[4], and others[5,6]. Noteworthy challenges in R-LIBS arise from intensity clamping in the filament core limited by MPI of air molecules[9], instabilities in directed energy delivery for greater peak powers which lead to stochastic formation of multiple filaments[9,22], and emission from atmospheric species from the filament and target plasmas[2,3,9,14], which contributes to background in optical emission spectroscopy.
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