“…The focused irradiance on the copper surface is estimated to W cm −2 , assuming 10% of the remaining energy of the input pulse lies within the filament core of diameter 100 μm. This result compares well with the expected clamped intensity reported in several other works 23 , 24 , 26 . Figure 2 Microscope images of damage induced by fs-filament ablation.…”
Section: Resultssupporting
confidence: 92%
“…The intensity-clamped filament core ( I ∼ 10 13 − 10 14 W cm −2 ) is surrounded by an energy reservoir 23 , 24 , which refills core channels obstructed or perturbed by obstacles such as atmospheric water droplets 25 . The reservoir, which has a lower intensity than the core, often fails to overcome the ablation threshold of solid targets and contributes less toward ablation and may instead only heat the target surface 26 . This presents a challenge for R-LIBS since a part of the energy from the pulse from the surrounding reservoir may not contribute toward plasma formation.…”
Section: Introductionmentioning
confidence: 99%
“…Valenzuela et al . 26 provided a comparison of ablation mechanisms for various focusing configurations of ultrashort pulses including slow or loosely focused as well as freely propagating filaments. Weidman et al .…”
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 P
cr. Despite the stochastic nucleation of multiple filaments at peak-powers greater than 16 P
cr, 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.
“…The focused irradiance on the copper surface is estimated to W cm −2 , assuming 10% of the remaining energy of the input pulse lies within the filament core of diameter 100 μm. This result compares well with the expected clamped intensity reported in several other works 23 , 24 , 26 . Figure 2 Microscope images of damage induced by fs-filament ablation.…”
Section: Resultssupporting
confidence: 92%
“…The intensity-clamped filament core ( I ∼ 10 13 − 10 14 W cm −2 ) is surrounded by an energy reservoir 23 , 24 , which refills core channels obstructed or perturbed by obstacles such as atmospheric water droplets 25 . The reservoir, which has a lower intensity than the core, often fails to overcome the ablation threshold of solid targets and contributes less toward ablation and may instead only heat the target surface 26 . This presents a challenge for R-LIBS since a part of the energy from the pulse from the surrounding reservoir may not contribute toward plasma formation.…”
Section: Introductionmentioning
confidence: 99%
“…Valenzuela et al . 26 provided a comparison of ablation mechanisms for various focusing configurations of ultrashort pulses including slow or loosely focused as well as freely propagating filaments. Weidman et al .…”
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 P
cr. Despite the stochastic nucleation of multiple filaments at peak-powers greater than 16 P
cr, 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.
“…However, it has to be mentioned that in SF laser beam the intensity clipping may be resulting from a one-off stripping of trailing pulse energy due to excessive plasma defocussing by the "overdense" plasma created by the leading part of the pulse and it could be different from stable filaments formed in loosely focused beams. Recently Valenzuela et al [7] showed that material removal rate by filament assisted ablation is smaller compared to SF beam generated plasma, where higher clamped intensity was available for ablation.…”
Section: Resultsmentioning
confidence: 98%
“…LIBS using fs lasers has been studied either using sharply focused beams or using filamentation [7][8][9][10][11]. Though it has been reported that filamentation LIBS (fLIBS) is a very promising method for long-distance material detection, the properties of fLIBS plumes are not well understood.…”
Ultrafast laser filament induced breakdown spectroscopy is a very promising method for remote material detection. We present characteristics of plasmas generated in a metal target by laser filaments in air. Our measurements show that the temperature of the ablation plasma is clamped along the filament channel due to intensity clamping in a filament. Nevertheless, significant changes in radiation intensity are noticeable, and this is essentially due to variation in the number density of emitting atoms. The present results also explain the near absence of ion emission but strong atomic neutral emission from plumes produced during fs LIBS in air.
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