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    Improved Si-Based Coating Materials for High Power Infrared Lasers

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    Data are presented to demonstrate that alloying of Si with H during thin film coating deposition reduces coating absorption at important infrared laser wavelengths such as 1.06, 1.315 and 2.7 μm by more than an order of magnitude compared to pure Si coatings. These results contradict earlier beliefs that the presence of H in Si was undesirable because of its association with H2O. It appears that absorption values approaching state-of-the-art for near-infrared coatings can now be obtained for a material with many attractive physical properties such as very high refractive index, outstanding hardness and scratch-resistance, glassy structure, non-hygroscopicity and general environmental stability and durability. In particular, an absorption coefficient of 3 cm−1 has been obtained at a wavelength of 2.7 μm for a Si1−xHx alloy with x = 0.12. The Si1−xHx coatings are made by reactive sputtering, and cannot be made by conventional evaporative techniques. Controlled deposition of coatings with specific compositions and optical properties is briefly described, and optical property-composition relationships are presented for the alloy mixing interval 0 < x < 0.4. The same sputtering system is used to deposit the low index material SiO2 by simple exchange of H2 for O2 in the sputtering gas, making possible straightforward multilayer coating fabrication. Reflectance spectra for Si1−xHx/SiO2 all-dielectric mirrors and dielectric-enhanced Au and Al mirrors are presented.


    absorption, coatings, composition, glassy structure, mirror fabrication, reactive sputtering, refractive index, Si, 1−x, H, x, alloys

    Author Information:

    Pawlewicz, WT
    Pacific Northwest Laboratory, Richland, Washington,

    Martin, PM
    Pacific Northwest Laboratory, Richland, Washington,

    Committee/Subcommittee: F01.02

    DOI: 10.1520/STP37271S