STP911

    Defect Damage Precursors in Visible-Wavelength Mirrors

    Published: Jan 1985


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    Abstract

    Video monitoring of pulsed visible-wavelength mirror damage has led to observation of illuminated defects as a precursor to observable microscopic damage. The blue-green illuminating radiation is produced in individual 0.5 μs pulses by a tunable flashlamp-pumped dye laser. The laser light is focused on multilayer dielectric or metal surfaces in an ⋍ 0.5 mm (D − 1/32) spot with a reproducible, flat-top spatial profile. An area slightly larger than the focal spot is viewed with a close-focusing Questar telescope equipped with a highly sensitive video camera. Typically, at nondamaging energy densities, defect sites within the focal spot area appear to be brightly illuminated at the laser wavelength. In dielectric mirrors, the illumination pattern depends on the laser wavelength, suggesting a sensitivity to defect position with respect to the standing wave field. At higher energy densities, laser damage originates only at certain defect sites, while other areas fail to damage even after many laser pulses. This paper presents results of an experimental characterization of the described phenomena.

    Keywords:

    dielectric mirrors, laser damage, nondestructive test, visible mirrors


    Author Information:

    Marrs, CD
    Michelson Laboratory, Physics Division Naval Weapons Center, China Lake, California

    Porteus, JO
    Michelson Laboratory, Physics Division Naval Weapons Center, China Lake, California

    Palmer, JR
    Michelson Laboratory, Physics Division Naval Weapons Center, China Lake, California


    Paper ID: STP28992S

    Committee/Subcommittee: E13.01

    DOI: 10.1520/STP28992S


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