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Pulsed D/sub 2/-F/sub 2/ chain-laser damage to coated window and mirror components

Technical Report ·
OSTI ID:5785914
Large-spot laser damage thresholds were measured for bowl-feed-polished CaF/sub 2/ and sapphire windows (bare and antireflection-coated) and for highly polished copper mirrors (bare and carbyne-coated) at DF chain-laser wavelengths (3.58-4.78 ..mu..m). Commercially available antireflection-coated CaF/sub 2/ and Al/sub 2/O/sub 3/ samples were found to have damage thresholds from 17 to 28 J/cm/sup 2/. Significantly larger damage thresholds were observed for uncoated, polished samples of Al/sub 2/O/sub 3/, but damage resistance of uncoated polished CaF/sub 2/ was found to equal that of the best antireflection-coated CaF/sub 2/ samples. A highly polished copper mirror had the highest damage threshold of all the materials tested, i.e., 58 J/cm/sup 2/. Carbyne films of diamond-like hardness, a type of carbon coating, were applied to polished copper mirrors and bowl-feed-polished CaF/sub 2/ surfaces. The carbyne coatings prepared in this work contained numerous carbon-bearing particles that were easily damaged (approx.10 J/cm/sup 2/). However, regions of the irradiated carbyne film that were free of carbon particles withstood high laser fluences (25 J/cm/sup 2/).
Research Organization:
Aerospace Corp., El Segundo, CA (USA). Aerophysics Lab.
OSTI ID:
5785914
Report Number(s):
SD-TR-83-92; ON: DE85901412
Country of Publication:
United States
Language:
English