SEDL / STP / STP1028-EB / STP18558S

Spectral Emission Studies of Optical Coating Defects

Marrs, CD
Naval Weapons Center, China Lake, California

Walker, SJ
Naval Weapons Center, China Lake, California

Moran, MB
Naval Weapons Center, China Lake, California

Porteus, JO
Naval Weapons Center, China Lake, California

Pages: 6    Published: Jan 1988

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Abstract

Video monitoring of pulsed visible-wavelength mirror damage led to the previously reported observation of illuminated coating defects as precursors to microscopic damage. Typically, many defects are observed in the laser interaction area, but only a few act as damage initiators. The present study seeks to identify the latter defects via any special characteristic of their laser-excited emission spectra that may serve as a recognizable signature. The ability to make such recognition nondestructively is crucial to producing optical coatings that perform at intrinsic damage levels. The video microscopy apparatus and methodology for measuring emission spectra of individual defects will be described. Results from various dielectric mirrors will be presented, including conclusive evidence that defect illumination is primarily the result of defect scattering. The dependence of defect image intensity on laser wavelength is examined more closely.