STP1028: Amorphous Silicon for CO2 Laser Mirror Coatings

    Dutois, F
    Laboratoires de Marcoussis - Centre de Recherches de la C.G.E., Marcoussis,

    Mouchart, J
    Laboratoires de Marcoussis - Centre de Recherches de la C.G.E., Marcoussis,

    Pointu, B
    Laboratoires de Marcoussis - Centre de Recherches de la C.G.E., Marcoussis,

    Villela, G
    Laboratoires de Marcoussis - Centre de Recherches de la C.G.E., Marcoussis,

    Pages: 8    Published: Jan 1988


    Abstract

    High power CO2 laser require mirrors with high reflectivity, high laser damage threshold and efficient mechanical and chemical protection. Enhanced metallic coatings are generally used.

    Amorphous silicon thin films are hard, with low porosity and have a high refractive index: unfortunately the low absorption at 10.6 μm is however too high for quarterwave layer at that wavelength.

    When associated with a classical transparent but softer high index material such as ZnSe or ZnS, amorphous silicon can nevertheless be used in order to design the last composite high index quaterwave. Theoretical calculations predict an optimum reflectance for a fixed a : Si : H thickness.

    The amorphous silicon thickness is thin enough to obtain a high reflectivity coating although its absorption, but thick enough to provide a good chemical and mechanical protection. Besides, experimentally determined that such enhanced coatings have a high laser damage threshold level.

    Keywords:

    amorphous silicon, CO, 2, laser mirrors, humidity test, laser damage threshold, optical coating, reflectivity


    Paper ID: STP18569S

    Committee/Subcommittee: F01.06

    DOI: 10.1520/STP18569S


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