Expansion dynamics of ultrafast laser produced plasmas in the presence of ambient argon

Abstract

We investigated the expansion dynamics of fs laser ablated brass plasma in Ar at various pressure levels ranging from 10−5 Torr to atmospheric conditions using time-resolved and spectrally resolved two-dimensional imaging. Significant changes in plume morphology were noticed at varying pressure levels which included free expansion, spherical to cylindrical geometry changes, sharpening, and confinement. The temporal evolution of excited Cu and Zn species in the plume were imaged using narrow band-pass interference filters, and their hydrodynamic expansion features were compared. 2D imaging coupled with monochromatic line selection showed velocity differences, uneven distribution, and aspect ratio differences among the plume species. Plume morphological changes were found to be significant at intermediate pressure levels (∼10 Torr) where plasma emissivity was found to be maximum. The expansion features of plume were compared with various models and found to be generally in good agreement.

Characterization of ultrafast laser-ablation plasma plumes at various Ar ambient pressures

“…In this paper, we extend our earlier work 26 and report the time and space resolved emission features of fs laser ablated brass plasma plumes at various Ar background pressure levels ranging from vacuum to atmospheric conditions. Spectrally integrated and wavelength dispersed 2D imaging of plasma self-emission showed collisional excitation of plasma plumes and confinement effects.…”

“…Detailed plume hydrodynamics study about fs LPP in Ar ambient has been provided in our earlier work. 26 Figure 1 shows the time evolution of fs laser produced brass plumes, spectrally integrated in the range of 350-900 nm, at various Ar pressure environments (vacuum, 0.1 Torr, 0.5 Torr, 10 Torr, 100 Torr, and 760 Torr Ar) from the onset of plasma formation to 1 ls. It can be seen that the plume expands freely at vacuum conditions with a forward bias.…”

“…25 Recently, we reported the expansion dynamics of fs LA plumes at various Ar pressure levels and indicated that the pressure of the background plays a critical role in plume hydrodynamics. 26 The temporal evolution of various species in the plume (Cu and Zn) was imaged using narrow bandpass interference filters and a comparison of their hydrodynamic expansion features showed velocity differences, uneven distribution, and aspect ratio differences. The expansion behaviors of the fs LA plume at various pressure levels were also compared with existing hydrodynamic models (adiabatic, blast, drag, and Predtechensky and Mayorov (PM) model); each model was capable of predicting the plume hydrodynamic features well at a certain range of pressure levels.…”

Impacts of Ambient and Ablation Plasmas on Short- and Ultrashort-Pulse Laser Processing of Surfaces

“…Later it was explained by the analogy with the dynamics of underexpanded jets that assumes transverse oscillations of the plume with distance from the target [31]. As shown in [32], the effect connected with the transverse oscillations of the ablation plumes upon its focusing in the presence of an ambient gas can also be observed at fs laser ablation regimes that calls for further studies. Such oscillations are a natural feature of plume expansion dynamics, which can be superimposed with the plasma pipe effect and most probably are damped with increasing ambient pressure.…”

Spatio-temporal evolution of uranium emission in laser-produced plasmas

“…The fundamental parameters (density and temperature) of laser ablation plumes are highly dynamic even in vacuum, where the expansion is isentropic and adiabatic. The expansion dynamics become much more complex in the presence of an ambient gas[33]. Typically, laser plasmas are hotter and denser at closer distances to the target and at early times, and both temperature and density decay rapidly with time and space.…”