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3 June 1998 Nanosecond UV laser pulse interactions with dielectric single crystals
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Abstract
The interaction of nanosecond ultraviolet laser light with bulk optical materials is discussed for the example of fluoride crystals. Absorption and thermoelastic response of the crystals are related to the laser damage threshold. It is shown that this threshold is most limited by defects resulting from surface preparation. Cleavage of crystals produces atomically flat terraces with highest damage thresholds (> 40 J/cm2 for ns-pulses at 248 nm) while cleavage steps and tips result in a dramatic local reduction of damage resistivity. Conventional polishing introduces contamination, scratches and dislocations yielding damage thresholds of typically 10 to 15 J/cm2. Advanced preparation techniques like chemo-mechanical polishing and precision grinding provide surfaces with a damage threshold uniform over large areas that is close to that of cleavage terraces. In all cases the damage threshold is determined by light absorption of defect-induced electronic states energetically located in the band gap of the insulator. Band gap states in calciumdifluoride are investigated by ultraviolet photoelectron spectroscopy and luminescence spectroscopy and surface quality is monitored by scanning electron and scanning force microscopy. Laser damage thresholds obtained for differently prepared surfaces are related to their structural and electronic properties and the primary mechanisms of energy uptake from the laser light are discussed.
© (1998) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Michael Reichling "Nanosecond UV laser pulse interactions with dielectric single crystals", Proc. SPIE 3274, Laser Applications in Microelectronic and Optoelectronic Manufacturing III, (3 June 1998); https://doi.org/10.1117/12.309491
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