STP1015

    Correlation Between Local HeNe Scatter and Defect-Initiated Laser Damage at 2.7 μm

    Published: Jan 1988


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    Abstract

    Evidence of a correlation between defect-initiated pulsed laser damage and local predamage scatter in multilayer infrared mirror coatings was reported last year at this conference. Analysis of a much larger data base confirms this result on certain sample types over a substantial range of energy densities above the damage onset. Scatter signals from undamaged test sites were obtained using an HeNe scatter-probe damage monitor with a focal spot that nearly coincides with the 150-μm-diameter (D1/e2) focal spot of the damaging beam. Subsequent damage frequency measurements (1-on-1) were made near normal or at 45-deg incidence with 100-ns pulses at 2.7-μm wavelength. The correlation is characterized by an increase in damage frequency with increasing predamage scatter signal. Characteristics of the correlation are compared with a simple model based on focal spot intensity profiles. Conditions that limit correlation are discussed, including variable scatter from defects and background scatter from diamond-turned substrates. Results have implication for nondestructive defect detection and coating quality control.

    Keywords:

    damage correlation, defect scattering, laser-induced damage, multilayer dielectric coatings, nondestructive quality control, optical defects, scatter probe


    Author Information:

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

    Spiker, CJ
    Michelson Laboratory, Physics Division Naval Weapons Center, China Lake, California

    Franck, JB
    Michelson Laboratory, Physics Division Naval Weapons Center, China Lake, California


    Paper ID: STP18787S

    Committee/Subcommittee: F01.11

    DOI: 10.1520/STP18787S


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