STP759

    Characterization of Small Absorptions in Optical Coatings

    Published: Oct 1981


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    Abstract

    Probably the main causes of laser damage in thin films used as optical coatings are impurities and non-stoichiometry, especially at interfaces. This paper considers the problems of identifying absorbing species, locating them in the optical structure and measuring the amount of absorbing species present. The ability to have large electromagnetic fields of the desired distribution in a multilayer system is used to optimize multiple reflection spectroscopy for the characterization of thin layers. The absorption coefficient caused by impurities in several Th F4 films are calculated as a function of angle of incidence and polarization. The position of these impurities is predicted by comparing the absorption coefficients measured with several techniques. The method is general and can be applied to give accurate results on systems of multiple phases and varying substrate. While the method is valid for general stratified media, its accuracy depends upon the information content of the particular reflection spectrum.

    Keywords:

    Absorption, coatings, internal reflection spectroscopy, silicon monoxide, thorium fluoride, zinc selenide, zinc sulfide


    Author Information:

    Anderson, WJ
    United States Air Force Academy, Colorado,

    Hansen, WN
    United States Air Force Academy, Colorado,


    Paper ID: STP37025S

    Committee/Subcommittee: F01.02

    DOI: 10.1520/STP37025S


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