Optical study of calcium precipitates in additively colored CaF2 crystals

The absorption spectra and microscopic images of calcium precipitates in CaF2 crystals additively colored in a heat-pipe setup at various coloring regimes are studied. The effect of two main parameters of coloring procedure, calcium vapor pressure and temperature, is found to be different. Higher values of both parameters increase the number of anion vacancies and electrons introduced into the crystal during the procedure, hence increasing also the concentration of calcium precipitates formed at the transformation of accumulations of these components. However, the pressure rise results in the concentration growth of calcium ions converted into colloidal particles, while the increase of temperature produces mainly calcium rods. The specific features of a surface layer of colored crystal depending on coloring regime are discussed. (C) 2018 Optical Society of America