Morphology of laser-produced carbon nanoparticle plasmas and high-order harmonic generation of ultrashort pulses in clustered media

Abstract

We analyse the morphology of the laser plasmas produced on surfaces containing various carbon clusters (nanotubes, nanofibres, fullerenes, and nanoparticles). It is shown that the presence of C5–C25 nanoparticles in the laser plasmas coincides with the enhancement of harmonics in the spectral range of 40–80 nm. We suggest that these nanoparticles, rather than larger clusters, play a decisive role in the observed growth of harmonic yield.

Probing Laser Plasma Dynamics Using High-Order Harmonics Generation in Carbon-Containing Nanomaterials

“…The moderate fluencies of nanosecond pulses also increased the lifetime of the targets and provided better survival of the original nanostructures being ablated and spread in the plasma plume without their destruction. It was demonstrated that, in the case of laser ablation of C 60 , MW CNT, CNF, and DN [25] at the experimental conditions similar to ours, the transmission electron microscopy analysis of deposited debris has shown that laser-produced plumes contained the original nanostructures.…”

“…Earlier reported TOFMS spectra have demonstrated the similarities between the MW CNT and CNF, with the presence of small carbon C n fragments (with n varied up to 20) and no ions higher than low-sized carbon clusters in the mass spectra up to 5000 mass/charge units [25]. Additionally, the emission from ablated MW CNT and C 60 targets showed almost similar spectra (Figure 2), with strong relative lines for CIII and CIV transitions.…”

“…Earlier, in the case of C 60 ablation at conditions similar to ours, TOFMS demonstrated the presence of preferably C 26 + fragments and smaller amount of C 60 + ions, alongside the neutral nanoparticles, in LIP [25]. In order to provide a qualitative explanation of the obtained HHG results we use the semiclassical model of HHG in isotropic medium [27].…”

“…In this table, we include the optimal fluencies for each studied sample. It was demonstrated in [23,25,26] by time-of-flight mass spectroscopy (TOFMS) that LIPs from the graphite surface contain, along with neutral carbon atoms and its ions, different C n clusters and their ions. The number of carbon atoms in such clusters varies from n = 2 up to n = 20, and for strong excitation n could even reach 100.…”