Interaction of wide band gap single crystals with 248 nm excimer laser irradiation. VII. Localized plasma formation on NaCl single crystal surfaces

Journal Article · Thu Feb 15 04:00:00 EST 2001 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.1340599· OSTI ID:40204925

Kawaguchi, Y; Dawes, M L; Langford, S C; Dickinson, J T

Wide band gap insulators containing defects exposed to nanosecond pulses of UV laser radiation at fluences close to the damage threshold often display highly localized flashes of light. In this work, we show that flashes observed during irradiation of cleaved, single crystal NaCl at relatively low fluences are due to localized plume fluorescence. By comparing time-resolved optical images of this fluorescence with subsequent scanning electron microscope images of surface topography, we show that these flashes are often associated with micron-dimension surface and near-surface damage, typically associated with cleavage steps. With continued laser irradiation, plume fluorescence at previously damaged regions usually grows stronger from pulse to pulse. In some cases, weak plume fluorescence disappears after one laser pulse, and may or may not reappear with continued irradiation. We interpret these results in terms of localized laser absorption by deformation-induced defects generated during cleavage. Deliberately deformed material, produced by indentation, is damaged at considerably lower laser fluences, consistent with this interpretation. We suggest that mobile excitations produced by laser absorption preferentially decay along dislocation cores, which strongly localizes laser-induced thermal stresses and damage.

• Sponsoring Organization: (US)
• OSTI ID: 40204925
• Journal Information: Journal of Applied Physics, Journal Name: Journal of Applied Physics Journal Issue: 4 Vol. 89; ISSN 0021-8979
• Publisher: The American Physical Society
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ELECTRON MICROSCOPES
EXCIMER LASERS
FLUORESCENCE
IRRADIATION
LASER RADIATION
LASERS
MONOCRYSTALS
PLUMES
THERMAL STRESSES