STP1141

    An Understanding of the Abnormal Wavelength Effect of Overcoats

    Published: Jan 1991


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    Abstract

    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.

    Keywords:

    laser damage, optical coating, overcoat, wavelength effect


    Author Information:

    Wu, ZL
    Shanghai Institute of Optics and Fine Mechanics, Academia Sinica, Shanghai,

    Freie Universität Berlin, Berlin,

    Reichling, M
    Freie Universität Berlin, Berlin,

    Fan, ZX
    Shanghai Institute of Optics and Fine Mechanics, Academia Sinica, Shanghai,

    Wang, ZJ
    Shanghai Institute of Optics and Fine Mechanics, Academia Sinica, Shanghai,


    Paper ID: STP23627S

    Committee/Subcommittee: F01.06

    DOI: 10.1520/STP23627S


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