Study of Surface Finishing and Coating of DF Laser Windows.
Abstract
This report summarizes a three-year investigation into the absorption losses in thin film coatings and surfaces of highly transparent materials at 3.8 microns. The primary emphasis during the first two years was on the minimization of thin film coating losses with the result that it is now possible to achieve film absorptions at DF laser wavelengths of nearly 0.01%/surface. In addition, attenuated total reflection studies performed in cooperation with the Naval Research Laboratory yielded information on the nature and cause of surface absorption in highly transparent coatings and bulk materials. The majority of this report is devoted to additional studies on surface absorption and methods that might be used to harden the surfaces of transparent materials. Surface absorption was measured in KCl and CaF2 that had been selectively contaminated by either H2O, D2O, C2H5OH, CH3OH, or NH4OH. Although increases in surface absorption of as much as 100% resulted for hydrocarbon contamination, a smaller increase than expected resulted for H2O and D2O contamination. The surface hardening experiments involved measuring delayed failure in coated (Al2O3) and uncoated SrF2 and CaF2 substrates. No definitive conclusions could be drawn regarding these results because the starting static loads were too high. All the tests were not completed.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 01, 1978
- Accession Number
- ADA058999
Entities
People
- J. A. Harrington
- M. Braunstein
Organizations
- HRL Laboratories