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Correlation Between Local HeNe Scatter and Defect-Initiated Laser Damage at 2.7 μm
Porteus, J
Michelson Laboratory, Physics Division Naval Weapons Center, California

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

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


Pages: 11    Published: Jan 1988


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Source: STP1015-EB


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

Paper ID: STP18787S
Committee/Subcommittee: F01.11
DOI: 10.1520/STP18787S
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