Accession Number : AD0917927

Title :   Low-Absorption Coating Technology.

Descriptive Note : Final rept. 22 May 72-22 May 73,

Corporate Author : HUGHES RESEARCH LABS MALIBU CALIF

Personal Author(s) : Braunstein,M.

Report Date : MAR 1974

Pagination or Media Count : 129

Abstract : The results reported here represent significant advances in the state of the art of high-power laser reflectors. An improvement in the absorptance for the enhanced reflectivity multilayer dielectric mirrors from 0.005 at 10.6 micrometers at the beginning of the study to a value as low as 0.0012 at 10.6 micrometers for Ag/(ThF4/CdTe) cubed has been achieved. The absorptance improvement from 0.005 to 0.0012 has been shown to be due to improvements in the purity of the ThF4 and CdTe dielectric materials; film deposition techniques are shown to be critical and must be carefully controlled. Further improvements in material purity or film deposition techniques can be expected to lower absorptance even more. Results are presented for a variety of new coatings with potential application at 10.6 micrometers . These coatings include the promising reflector Al/(KCl/As2S3) to the 4th power which has shown 0.0016 absorptance and a high-energy density damage threshold of about 50J/sq cm. Results are presented from the laser damage study for damage thresholds for the coatings and reflectors produced during the course of the program. The program goal, which was to produce reflectors having 99.9% reflectance at 10.6 micrometers was almost met by our achieving 99.88% for a Ag/(ThF4/CdTe) cubed reflector. Rigorous control of starting materials used for the coatings and the deposition techniques was found to be essential for the preparation of the high reflectance, low absorptance coatings.

Descriptors :   (*Coatings, Reflectors), (*Lasers, *Reflectors), Absorption, Low energy, Absorbers(Materials), Reflectivity, Dielectric properties, Mirrors, Silver, Thorium compounds, Phosphates, Cadmium tellurides, Purity, Fluorides, Thin films, Deposition, Aluminum alloys, Potassium compounds, Chlorides, Arsenic compounds, Sulfides, High energy, Density, Damage

Subject Categories : Lasers and Masers
      Coatings, Colorants and Finishes

Distribution Statement : APPROVED FOR PUBLIC RELEASE