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Proceedings Paper

Application of photothermal probe beam deflection technique for the high-sensitive characterization of optical thin films with respect to their optical, thermal, and thermoelastic inhomgeneities
Author(s): Eberhard Welsch; K. Ettrich; M. Peters; Holger Blaschke; W. Ziegler; Axel Bodemann; Michael Reichling
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Paper Abstract

Two-dimensional cw photothermal surface displacement (PTD) scans with high spatial resolution provide a new quality for thin-film characterization. This is demonstrated for optical single-layer films of MgF2 and for 248 nm high-reflecting Al2O3/SiO2 multilayer coatings. Inhomogeneities of the films were detected with a lateral resolution better than 2 micrometers . Photothermal images reveal that Al2O3/SiO2 coatings with low damage thresholds differ above all in the amplitude of the PTD background signal whereas high-damage-threshold-coatings excel in a noticeable decrease in defect concentration. On the other hand, pulsed thermal MIRAGE technique is shown to be capable to yield complementary information with respect to the subdamage behavior as well as the onset of UV damage in Al2O3/SiO2 laser mirrors. Thus, the physical origin of the UV radiation breakdown in optical thin films can be elucidated.

Paper Details

Date Published: 4 November 1994
PDF: 12 pages
Proc. SPIE 2253, Optical Interference Coatings, (4 November 1994); doi: 10.1117/12.192178
Show Author Affiliations
Eberhard Welsch, Friedrich-Schiller-Univ. (Germany)
K. Ettrich, Friedrich-Schiller-Univ. (Germany)
M. Peters, Friedrich-Schiller-Univ. (Germany)
Holger Blaschke, Friedrich-Schiller-Univ. (Germany)
W. Ziegler, Friedrich-Schiller-Univ. (Germany)
Axel Bodemann, Fraunhofer-Einrichtung fuer Angewandte Optik und Feinmechanik (Germany)
Michael Reichling, Freie Univ. Berlin (Germany)

Published in SPIE Proceedings Vol. 2253:
Optical Interference Coatings
Florin Abeles, Editor(s)

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