Certain spaceborne telescope designs require that dielectric-coated lenses be exposed to the energetic electrons and protons associated with the space environment. Test coupons that were exposed to a simulated space environment showed extensive pitting as a result of dielectric breakdown. A typical pit was 50–100 μm at the surface and extended to the substrate material, in which a 10-μm-diameter melt region was found. Pitting was not observed on similar samples that had also been overcoated with a transparent conductive thin film. Measurement of the bidirectional reflectance distribution transfer function showed that pitting caused a fivefold to tenfold increase in the scattering of visible light.
© 2002 Optical Society of America
Peter D. Fuqua, Nathan Presser, James D. Barrie, Michael J. Meshishnek, and Dianne J. Coleman, "Pit formation observed in a multilayer dielectric coating as a result of simulated space environmental exposure," Appl. Opt. 41, 3142-3149 (2002)