Accession Number : ADA138911

Title :   Pulsed D2-F2 Chain-Laser Damage to Coated Window and Mirror Components.

Descriptive Note : Technical rept.,


Personal Author(s) : Amimoto,S T ; Whittier,J S ; Whittaker,A ; Chase,A ; Hofland,R , Jr

PDF Url : ADA138911

Report Date : 15 Dec 1983

Pagination or Media Count : 27

Abstract : Large-spot laser damage thresholds were measured for bowl-feed-polished CaF2 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 micrometers). The chain reaction between F2 and D2 was initiated by a magnetically confined electron beam, producing DF-laser outputs of 10 to 20 J in pulses of 0.6 to 0.9 microseconds (FWHM) duration. Energy extracted from a transmission-coupled unstable resonator was focused by means of a CaF2 lens. A soft-aperture technique was employed to suppress effects of Fresnel diffraction so that uniform (top-hat) intensity profiles were obtained along the focusing beam. With this laser system, commercially available antireflection-coated CaF2 and Al2O3 samples were tested and found to have damage thresholds from 17 to 28 J/sq cm 2. Significantly larger damage thresholds were observed for uncoated, polished samples of Al2O3, but damage resistance of uncoated polished CaF2 was found to equal that of the best antireflection-coated CaF2 samples. A highly polished copper mirror had the highest damage threshold of all the materials tested, i.e., 58 J/sq cm 2.

Descriptors :   *Pulsed lasers, *Laser damage, Optical equipment components, Protective coatings, Damage control, Laser spots, Mirrors, Hydrogen fluoride lasers, Threshold effects

Subject Categories : Lasers and Masers

Distribution Statement : APPROVED FOR PUBLIC RELEASE