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

Technical Report · Thu Dec 15 04:00:00 EST 1983

OSTI ID:6737849

Amimoto, S T; Whittier, J S; Whittaker, A; Chase, A; Hofland, R Jr

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 micrometers). The chain reaction between F/sub 2/ and D/sub 2/ 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 CaF/sub 2/ 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 CaF/sub 2/ and Al/sub 2/O/sub 3/ 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 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/sq cm 2.

• Research Organization: Aerospace Corp., El Segundo, CA (USA). Aerophysics Lab.
• OSTI ID: 6737849
• Report Number(s): AD-A-138911/3; TR-0084(4930-01)-2
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
420300* -- Engineering-- Lasers-- (-1989)
COATINGS
GAS LASERS
LASER MIRRORS
LASERS
MIRRORS
PROTECTIVE COATINGS