Exploratory development of fusion cast calcium fluoride for 1. 06 micrometer pulsed laser optics. Progress report, December 25, 1976--March 25, 1977
Description: This program is an assessment of fusion cast polycrystalline calcium fluoride for optical components of 1.064 micrometer pulsed laser fusion systems. Task areas include casting of essentially stress-free 33 centimeter diameter, 5 centimeter thick ingots, developing surface finishing techniques for optically figured plane and spherical surfaces, and evaluating state-of-the-art antireflection coatings deposited onto specimens of the cast material. During the third quarter, three casting runs were completed in the large casting furnace, none of which was wholly successful. A decision to limit the remainder of the casting effort to six-inch (15-centimeter) diameter pieces was made. Two chemically homogeneous castings of CaF/sub 2//Nd were made in a second furnace. Diamond abrasive polishing techniques were used successfully to fabricate a 15-centimeter radius convex spherical surface on one polycrystalline casting and a quarter wave plane surface on a second. Both surfaces were free of grain boundary relief which is commonly produced by standard techniques. Antireflection coatings obtained from two vendors were found to be physically durable and optically uniform. The components of these coatings are those also used by the vendors for their laser damage resistant coatings on glass, so it is reasonable to anticipate that they will be damage resistant on the fluoride as well. Damage testing will be carried out during the final quarter of the program.
Date: April 1, 1977
Creator: Willingham, C. B.
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