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Proceedings Paper

Nanosecond UV laser pulse interactions with dielectric single crystals
Author(s): Michael Reichling
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Paper 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.

Paper Details

Date Published: 3 June 1998
PDF: 8 pages
Proc. SPIE 3274, Laser Applications in Microelectronic and Optoelectronic Manufacturing III, (3 June 1998); doi: 10.1117/12.309491
Show Author Affiliations
Michael Reichling, Freie Univ. Berlin (Germany)

Published in SPIE Proceedings Vol. 3274:
Laser Applications in Microelectronic and Optoelectronic Manufacturing III
Jan J. Dubowski; Peter E. Dyer, Editor(s)

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