SYMPOSIA PAPER Published: 01 January 1991
STP23627S

An Understanding of the Abnormal Wavelength Effect of Overcoats

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In this paper wavelength dependent damage phenomena in SiO2 overcoats on TiO2/SiO2 and ZrO2/SiO2 HR coatings are systematically investigated with the help of various techniques, including a dynamical study of the damage process by time-resolved photothermal deflection technique, microscopic analysis of the absorption sites by cw-modulated photo-thermal microscopy, and observation of the coating microstructures and damage morphology by TEM and Nomarski optical microscopy. From the data for 355 nm and 1.06 μm radiation and a theoretical calculation of the temperature distribution inside the coating, we conclude that damage occurs first either in the HR coating or in the overcoat depending on the wavelength of the incident radiation. The influence of the local absorption sites, the interface morphology, as well as the heat transfer on the damage thresholds is discussed. The interpretation is supported by additional results on samples with various coating designs including SiO2 undercoats.

Author Information

Wu, ZL
Shanghai Institute of Optics and Fine Mechanics, Academia Sinica, Shanghai, PRC Freie Universität Berlin, Berlin, FRG
Reichling, M
Freie Universität Berlin, Berlin, FRG
Fan, ZX
Shanghai Institute of Optics and Fine Mechanics, Academia Sinica, Shanghai, PRC
Wang, ZJ
Shanghai Institute of Optics and Fine Mechanics, Academia Sinica, Shanghai, PRC
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Details
Developed by Committee: F01
Pages: 200–213
DOI: 10.1520/STP23627S
ISBN-EB: 978-0-8031-5179-6
ISBN-13: 978-0-8194-0532-6