Time-resolved shadowgraphic study of femtosecond laser ablation of aluminum under different ambient air pressures

Femtosecond pulse laser ablation of aluminum under different ambient air pressures between 1 atm and 4×10 −4 Pa is investigated using a femtosecond time-resolved shadowgraphic method. It is observed that as the ambient air pressure decreases, the contact front becomes more and more distinct for a ce...

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Bibliographic Details
Published inJournal of applied physics Vol. 109; no. 5; pp. 053113 - 053113-8
Main Authors Wu, Zehua, Zhu, Xiaonong, Zhang, Nan
Format Journal Article
LanguageEnglish
Published United States American Institute of Physics 01.03.2011
Subjects
ABLATION
AIR
ALUMINIUM
COHERENT SCATTERING
CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
DEPOSITS
DIFFRACTION
DISPERSIONS
ELECTROMAGNETIC RADIATION
ELECTRON MICROSCOPY
ELEMENTS
FLUIDS
GASES
LASER RADIATION
METABOLISM
METALS
MICROSCOPY
MIXTURES
PRESSURE DEPENDENCE
PRESSURE RANGE
PULSES
RADIATIONS
RESOLUTION
SCATTERING
SPECTRA
STRAINS
TIME DELAY
TIME RESOLUTION
TIMING PROPERTIES
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Summary:Femtosecond pulse laser ablation of aluminum under different ambient air pressures between 1 atm and 4×10 −4 Pa is investigated using a femtosecond time-resolved shadowgraphic method. It is observed that as the ambient air pressure decreases, the contact front becomes more and more distinct for a certain pressure range, demonstrating that the confinement effect of the ambient air to the ablated target material can play a critically important role in the laser ablation process. It is also found that the concentric and semicircular stripe pattern, which results from the diffraction of the probe beam by the expanding plume of a specific material state and is typically observed in the shadowgraphs for 1-2 ns delay time, gradually blurs and disappears while the ambient air pressure decreases from 1 atm to 7000 Pa. If a prepulse or a relatively large pulse pedestal exists before the main pulse, however, the stripe pattern can still be observed even though the ambient air pressure is 5×10 -4 Pa. It is thus inferred that what contributes to the formation of the unique stripe pattern is a mixture of the ejected target material and ionized background gas induced by the femtosecond laser ablation.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.3554442