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Changes in optical interference coatings exposed to 193-nm excimer laser radiation


Exarhos, G.J. ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
Laser-Induced Damage in Optical Materials 1998
Bellingham, Wash.: SPIE, 1999 (SPIE Proceedings Series 3578)
ISBN: 0-8194-3045-5
Annual Boulder Damage Symposium <30, 1998, Boulder/Colo.>
Conference Paper
Fraunhofer IOF ()
UV-coatings; UV-conditioning; UV-degradation

The exposure of optical interference coatings to low-fluence DUV-radiation reveals changes of thin layer properties due to interactions between radiation field and thin film structure. An experimental set up for irradiating antireflective as well a high reflective coatings with 193nm excimer laser was used in order to study permanent cumulative changes in optical coatings at fluences ranging from 20mJ/cm2 with up to 240 106 laser pulses. The optical ex-situ monitoring of radiation induced modifications enabled the differentiation of coating specific and substrate inherent alteration effects. The identification of conditions as well as degradation processes during the exposure could be achieved for several types of DUV-coating materials. They were deposited with an ultra low loss evaporation process onto calcium fluoride and fused silica substrates. Fluoride coating included LaF3, Na3AlF6, MgF2, AlF3 oxide coatings consisted of SiO2 and Al2O3 exclusively.