CZOCHRALSKI RUBY

The quality of Czochralski ruby was significantly improved during the report period. The gain resulted from closer controls on growth parameters, ambient atmosphere, and melt temperature. Crystals grown under preferred conditions are bubble-free and of high optical quality. Optical paths through 6-mm-diameter x 4-5 cm-long x .03-.04 wt percent Cr2O3, 60 degrees orientation rubies are uniform over the rod aperture to within a wavelength (CdI 6438A) or better. The passive beam divergence observed approaches the diffraction limit. 90 degrees and 0 degrees rubies grown on Verneuil seed rods are of lesser quality in that order. A rough estimate based on rocking-curve data indicates an 8second upper limit on mosaic structure in current ruby. The remaining optical inhomogeneity is due principally to chromium variations and probably residual stress. Sponsored in part by the DARPA.