Multithreshold Damage Measurements on As2S3, As2Se3, and NaF at HF and DF Wavelengths

    Published: Jan 1979

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    We previously reported on the deposition, absorption, and CO2-laser damage threshold for As2S3, As2Se3, and NaF coatings. It was shown that the damage threshold was much lower for coated than uncoated substrates and that the mechanism for damage was different in the coatings than in the substrates. We speculated that the damage in the coatings was related to the presence of micronsized crystalline defects distributed in the amorphous chalcogenide matrix. In this paper we report the results of damage measurements on these materials at 2.8 and 3.8 µm and identify two operating damage processes: “uniform” damage, which we associate with the amorphous chalcogenide matrix, and “selective” damage, which we associate with the crystalline defects. For single-layer films, we find that N/1 conditioning generally produces an increase in the damage thresholds. The wavelength dependence of multithreshold results in single-layer coatings of As2S3 and NaF suggests that improvement in threshold results from the thermal desorption of contaminating layers of water at 2.7 µm. However, for a dielectrically enhanced reflector containing quarter-wave layers of As2Se3, and NaF, N/1 conditioning promoted crystallite growth which resulted in a definite deterioration of N/1 thresholds.


    Absorption, arsenic selenide, arsenic trisulfide, defects, laser damage, sodium fluoride

    Author Information:

    Donovan, TM
    Michelson Laboratory, China Lake, CA

    Porteus, JO
    Michelson Laboratory, China Lake, CA

    Jernigan, JL
    Michelson Laboratory, China Lake, CA

    Ashley, EJ
    Michelson Laboratory, China Lake, CA

    Committee/Subcommittee: F01.02

    DOI: 10.1520/STP39118S

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