Abstract
Intracavity optics of e-beam-pumped high-energy KrF lasers should survive in a hostile environment of simultaneous irradiation by intensive UV laser light, scattered electrons, bremsstrahlung X-ray radiation, and permanent etching by a fluorine-containing working gas mixture. The present paper is focused on the research and development of high-optical-strength and fluorine-resistant AR coatings capable of protecting the fused silica windows and HR rare mirrors of these lasers against fluorine attack. The most promising coatings deposited by e-beam evaporation were ${{\rm NdF}_3}$-based compositions, which have low water content, good resistance to fluorine, and demonstrated the highest damage thresholds for AR coatings ${29.8}\,\,{{\rm J/cm}^2}$ in a large irradiation spot. Outstanding “water-free” coatings of ${{\rm MgF}_2}$ and ${{\rm Al}_2}{{\rm O}_3}$ were deposited by ${{\rm CO}_2}$ laser evaporation with preliminary laser treatment of substrates.
© 2020 Optical Society of America
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