Observation of nanosecond laser-induced phase explosion in aluminum

Porneala, Cristian; Willis, David A.

doi:10.1063/1.2393158

Cited by 156 publications

(81 citation statements)

References 10 publications

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“…The results above on the existence of a threshold fluence and the steep increase of the ablation rate upon increasing the fluence above the threshold value are consistent with previous work on metallic and non-metallic materials in different irradiation conditions [16,[19][20][21]. There, ablation was performed in vacuum conditions, and the fluence was varied via the pulse energy.…”

Section: Resultssupporting

confidence: 75%

“…Understanding and controlling the ablation rate is essential for micro-based on nanosecond laser ablation, and to determine the optimum parameters of the nanosecond laser-pulses that allow one to obtain high quality micropatterns on different metallic or non-metallic materials [8][9][10][19][20][21][22]. The experiments indicate that the ablation rate increases logarithmically with the fluence of the nanosecond pulses in the case of semiconductors and dielectrics [2,5,16], while for values of the fluence higher than a threshold there is a steep increase of the ablation rate [16,[19][20][21]. The wavelength of the laser has a significant influence on the ablation rate: the shorter the wavelength, the higher the ablation rate.…”

Section: Introductionmentioning

confidence: 99%

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Impact of the lasr wavelength and fluence on the ablation rate of aluminium

2008

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Abstract:The dependence of the ablation rate of aluminium on the fluence of nanosecond laser pulses with wavelengths of 532 nm and respectively 1064 nm is investigated in atmospheric air. The fluence of the pulses is varied by changing the diameter of the irradiated area at the target surface, and the wavelength is varied by using the fundamental and the second harmonic of a Q-switched Nd-YAG laser system. The results indicate an approximately logarithmic increase of the ablation rate with the fluence for ablation rates smaller than ∼6 µm/pulse at 532 nm, and 0.3 µm/pulse at 1064 nm wavelength. The significantly smaller ablation rate at 1064 nm is due to the small optical absorptivity, the strong oxidation of the aluminium target, and to the strong attenuation of the pulses into the plasma plume at this wavelength. A jump of the ablation rate is observed at the fluence threshold value, which is ∼50 J/cm 2 for the second harmonic, and ∼15 J/cm 2 for the fundamental pulses. Further increasing the fluence leads to a steep increase of the ablation rate at both wavelengths, the increase of the ablation rate being approximately exponential in the case of visible pulses. The jump of the ablation rate at the threshold fluence value is due to the transition from a normal vaporization regime to a phase explosion regime, and to the change of the dimensionality of the hydrodynamics of the plasma-plume. PACS

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Section: Resultssupporting

confidence: 75%

Section: Introductionmentioning

confidence: 99%

Impact of the lasr wavelength and fluence on the ablation rate of aluminium

2008

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“…The threshold behavior in laser ablation can be related to the sharp transition from a metastable superheated liquid to a two-phase mixture of liquid and vapor (explosive boiling) at a temperature of approximately 90% of the critical temperature, as predicted based on the classical nucleation theory [166][167][168][169] and confirmed in simulations [170]. Experimental observations of the existence of a threshold fluence for the onset of the droplet ejection, as well as a steep increase of the ablation rate at the threshold, have also been interpreted as evidence of the transition from normal vaporization to the phase explosion [169,[171][172][173].…”

Section: Phase Explosion and Laser Ablationmentioning

confidence: 80%

Atomic/Molecular-Level Simulations of Laser–Materials Interactions

Zhigilei

Lin

Ivanov

et al. 2009

Laser-Surface Interactions for New Materials Production

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Summary. Molecular/atomic-level computer modeling of laser-materials interactions is playing an increasingly important role in the investigation of complex and highly nonequilibrium processes involved in short-pulse laser processing and surface modification. This chapter provides an overview of recent progress in the development of computational methods for simulation of laser interactions with organic materials and metals. The capabilities, advantages, and limitations of the molecular dynamics simulation technique are discussed and illustrated by representative examples. The results obtained in the investigations of the laser-induced generation and accumulation of crystal defects, mechanisms of laser melting, photomechanical effects and spallation, as well as phase explosion and massive material removal from the target (ablation) are outlined and related to the irradiation conditions and properties of the target material. The implications of the computational predictions for practical applications, as well as for the theoretical description of the laser-induced processes are discussed. IntroductionShort-pulse lasers are used in a diverse range of applications, from advanced materials processing, cutting, drilling, and surface micro-and nanostructuring [1,2] to pulsed-laser deposition of thin films and coatings [3], laser surgery [4,5], and artwork restoration [6,7], and to the exploration of the conditions for inertial confinement fusion, with the world's most energetic laser system being built at the National Ignition Facility at Lawrence Livermore National Laboratory [8]. At the fundamental science level, short-pulse laser irradiation has the ability to bring material into a highly nonequilibrium state and provides a unique opportunity to probe the material behavior under extreme conditions. In particular, optical pump-probe experiments have been used to investigate transient changes in the electronic structure of the irradiated surface with high (often subpicosecond) temporal resolution [9][10][11][12][13], whereas recent advances in time-resolved X-ray and electron diffraction

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“…Experimental observations of the onset of the ejection of liquid droplets as well as a steep increase in the ablation rate are often interpreted as evidence of the transition from normal vaporization to phase explosion. 9,22,24,25 The results of hydrodynamic modeling 26,27 and molecular dynamic (MD) simulations 17,23,[28][29][30][31] of short pulse laser ablation confirm phase explosion as the dominant mechanism responsible for the material ejection at laser fluences below the values leading to substantial ionization and plasma formation. The results of MD simulations, in particular, provide detailed information on the dynamics of the explosive decomposition of the overheated surface region and characteristics of the ablation plume.…”

Section: Introductionmentioning

confidence: 99%

“…4 The mechanisms responsible for the material removal in laser ablation include an intensive evaporation from the irradiated surface at low laser fluences and/or long pulse durations, 5 an explosive decomposition of a surface region of the target into individual atoms or molecules and liquid droplets at higher fluences, [6][7][8][9] hydrodynamic sputtering 10,11 or expulsion of molten material due to the action of the evaporation or ablation recoil pressure, [12][13][14] an ejection of large droplets or fractured solid fragments caused by photomechanical effects, [15][16][17][18] as well as nonthermal processes related to photochemical reactions 19,20 or laser-induced charging and Coulomb explosion of a surface layer of the target. 21 The explosive boiling or "phase explosion", in particular, is commonly discussed as a primary mechanism of short pulse laser ablation of metal targets, [6][7][8][9][22][23][24] where the surface charging and Coulomb explosion are inhibited by the high mobility of the conduction band electrons. 21 This mechanism of material ejection involves an explosive decomposition of a surface region of the target superheated beyond the limit of thermodynamic stability of the target material (∼90% of the critical temperature) into a two-phase mixture of liquid and vapor.…”

Section: Introductionmentioning

confidence: 99%

Atomistic Modeling of Short Pulse Laser Ablation of Metals: Connections between Melting, Spallation, and Phase Explosion

2009

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The mechanisms of short pulse laser interactions with a metal target are investigated in simulations performed with a model combining the molecular dynamics method with a continuum description of laser excitation, electron-phonon equilibration, and electron heat conduction. Three regimes of material response to laser irradiation are identified in simulations performed with a 1 ps laser pulse, which corresponds to the condition of stress confinement: melting and resolidification of a surface region of the target, photomechanical spallation of a single or multiple layers or droplets, and an explosive disintegration of an overheated surface layer (phase explosion). The processes of laser melting, spallation, and phase explosion are taking place on the same time scale and are closely intertwined with each other. The transition to the spallation regime results in a reduction of the melting zone and a sharp drop in the duration of the melting and resolidification cycle. The transition from spallation to phase explosion is signified by an abrupt change in the composition of the ejected plume (from liquid layers and/or large droplets to a mixture of vapor-phase atoms, small clusters and droplets), and results in a substantial increase in the duration of the melting process. In simulations performed with longer, 50 ps, laser pulses, when the condition for stress confinement is not satisfied, the spallation regime is absent and phase explosion results in smaller values of the ablation yield and larger fractions of the vapor phase in the ejected plume as compared to the results obtained with a 1 ps pulse. The more vigorous material ejection and higher ablation yields, observed in the simulations performed with the shorter laser pulse, are explained by the synergistic contribution of the laser-induced stresses and the explosive release of vapor in phase explosion occurring under the condition of stress confinement.

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Observation of nanosecond laser-induced phase explosion in aluminum

Cited by 156 publications

References 10 publications

Impact of the lasr wavelength and fluence on the ablation rate of aluminium

Impact of the lasr wavelength and fluence on the ablation rate of aluminium

Atomic/Molecular-Level Simulations of Laser–Materials Interactions

Atomistic Modeling of Short Pulse Laser Ablation of Metals: Connections between Melting, Spallation, and Phase Explosion

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