Photochromism, bleaching and photorefractive recording in undoped Bi12TiO20 crystals in the visible and near infrared wavelength range

We describe the effect of radiation of different wavelengths in the visible and near infrared range over photochromism, bleaching and photorefractive recording on undoped Bi12TiO20 crystals. These experiments lead to a phenomenological description of the relevant photoactive centers in this material. At least an empty donor level 0.42 eV below the conduction band, some deeper donor levels up to 1.6 eV below the conduction band and an acceptor level 1 eV above the valence band were identified.