Energy Absorption and Propagation in Laser-Created Sparks

Bindhu, C. V.; Harilal, S. S.; Tillack, M. S.; Najmabadi, F.; Gaeris, A. C.

doi:10.1366/000370204872917

Cited by 81 publications

(54 citation statements)

References 36 publications

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“…3,4 Other important applications of LIP include pulsed laser deposition, 5 nanoparticle and cluster production, 6,7 and laser-induced breakdown spectroscopy ͑LIBS͒. 8 Laser-created plasma characteristics are strongly dependent upon several key parameters, including laser intensity, pulse duration and wavelength, target material and geometry, and the nature and pressure of any ambient gas. The plasma characteristics also vary with distance from the target surface, as well as with time following the onset of plume formation.…”

Section: Introductionmentioning

confidence: 99%

Spectroscopic characterization of laser-induced tin plasma

Harilal

O'Shay

Tillack

et al. 2005

Journal of Applied Physics

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155

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Optical emission spectroscopic studies have been carried out on a tin plasma generated using 1064-nm, 8-ns pulses from a Nd:yttrium aluminum garnet laser. Temperature and density were estimated from the analysis of spectral data. The temperature measurements have been performed by Boltzmann diagram method using singly ionized Sn lines, while density measurements were made using the Stark broadening method. An initial temperature of 3.2 eV and density of 7.7×1017cm−3 were measured. Temporal and spatial behaviors of electron temperature and density in the laser-generated tin plasma have been analyzed. Time evolutions of density and temperature are found to decay adiabatically at early times. The spatial variation of density shows approximately 1∕z dependence. The time-integrated temperature exhibits an appreciable rise at distances greater than 7 mm. This may be caused by the deviation from local thermodynamic equilibrium at larger distances from the target surface.

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Section: Introductionmentioning

confidence: 99%

Spectroscopic characterization of laser-induced tin plasma

Harilal

O'Shay

Tillack

et al. 2005

Journal of Applied Physics

Self Cite

155

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“…In laserinduced breakdown spectroscopy (LIBS), free electrons collide with neutral atoms and absorb energy from the laser resulting in gas ionization. This inverse Bremsstrahlung process dominates other gas ionization processes [1]. The first stage is breakdown as the gas is ionized, followed by laser energy absorption by the hot gas, and the last stage is detonation which results in plasma expansion and shock wave formation [2], [3].…”

Section: Introductionmentioning

confidence: 99%

Radial Variation of Refractive Index, Plasma Frequency and Phase Velocity in Laser Induced Air Plasma

Mathuthu

Raseleka

Forbes

et al. 2006

IEEE Trans. Plasma Sci.

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Abstract-Laser-induced breakdown spectroscopy (LIBS) is a nonintrusive technique that needs no sample preparation and even recently, quantitative measurements were done without the need for calibration standards. Much research has been done on the laser induced air plasma to study the spatial variation of plasma parameters in the axial direction of the laser beam. In this paper, we report investigation on the radial variation of the refractive index, plasma frequency, and phase velocity of a plasma during laser induced breakdown of air. The results show that the radial variations of the plasma frequency and refractive index are caused by the radial electron density gradient of the plasma. The radial variation of the electron density shows a noticeable depletion at the center of the focus which results in plasma phase velocities greater than the speed of light. Further from the plasma core the electron density diminishes to ambient density at the edges of the plasma. The mean full-width at half maximum (FWHM) for these plasma profiles was found to be about 1.2 mm. The results further reveal that the plasma has a concave parabollic electron density and a convex parabollic refractive index profile near the center of the laser axis, i.e., around a diameter of 0.5 mm.Index Terms-Laser-induced breakdown spectroscopy (LIBS), phase velocity, plasma frequency, refractive index.

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“…Even the slightly lobed features apparent in Fig. 7(B) are reminiscent of the reported glow of the two-lobed intensity patterns from time gate ICCD camera imaging [11]. Lastly, the melted region extends well beyond~300 µm the <150 µm wide evaporated pit, with a slight roughening of surface at the edges (near the dotted lines).…”

Section: Glancing Configurationmentioning

confidence: 53%

“…In Fig. 1(A) a YAG laser beam is focused through a 100 mm fused silica lens and the plasma cloud formed at focus while propagating backward [11]. The fused silica Corning 7980 sample (50 mm diameter, 10 mm thick) is brought in proximity to the gas plasma with a mechanized stage.…”

Section: Laser-induced Gas Plasma Configurationsmentioning

confidence: 99%

Laser-induced gas plasma etching of fused silica under ambient conditions

et al. 2012

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Laser machining of optics to mitigate surface defects has greatly enhanced the ability to process large optics such as those found in fusion-class lasers. Recently, the use of assist reactive gases has shown promise in enhancing manifold etching rates relative to ambient conditions for CW-laser exposures. However, these methods still require significant heating of the substrate that induce residual stress, redeposit coverage, material flow, and compromise the final surface finish and damage threshold. While very reactive fluorinated gases are capable to reduce treatment temperatures even further, they are also inherently toxic and not readily transferable to large processing facilities. In this report, we look at whether a short-lived gas plasma could provide the safe and effective etchant sought, while still reducing the thermal load on the surface. We test this approach using a YAG laserinduced gas plasma to act as a source of the etchant for fused silica, a common optical material. The configuration and orientation of the beam and optical apparatus with respect to the surface was critical in preventing surface damage while etching the surface. Results with N 2 and air gas plasmas are shown, along with a description of the various experimental implementations attempted.Keywords: silica, gas plasma, laser, etching, heat, thermal, machining *Correspondence: E-mail: elhadj2@llnl.gov; phone 1 925 422-0270; fax 1 925 423 0792

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Energy Absorption and Propagation in Laser-Created Sparks

Cited by 81 publications

References 36 publications

Spectroscopic characterization of laser-induced tin plasma

Spectroscopic characterization of laser-induced tin plasma

Radial Variation of Refractive Index, Plasma Frequency and Phase Velocity in Laser Induced Air Plasma

Laser-induced gas plasma etching of fused silica under ambient conditions

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