Color centers in Cu-doped Bi12SiO20 crystals

The present work is devoted to the investigation of stable color centers that are induced by light illumination of Cu-doped Bi12SiO20 (BSO) single crystals. The induced stable absorption is characterized by wide band with maximum at 21,500 cm−1 and optical bleaching in the near-infrared region. We clearly attribute the observed changes to the increase in the Cu+ concentration and decrease the Cu2+ concentration as a result of electron trapping by Cu2+ ions (Cu2++e−→Cu+). The effect of heating in air on the absorption of light is studied. The decay activation energy of photochromic centers in BSO:Cu crystals is obtained from the transmission spectra.