Light-induced infrared absorption in Ru-doped Bi12TiO20 single crystals

This paper presents measurements of light-induced near infrared absorption in Bi₁₂TiO₂₀ (BTO) crystals highly doped with Ru. According to the light-induced absorption dark decay measurements it is supposed that Ru creates two different levels: Ru³⁺4+/ and Ru⁴⁺5+/ located "more shallow" than the deep one with respect to the valence band. Each of these two levels has different contribution to the light-induced absorption and different thermal ionization rates β, so the interaction between them can be neglected. After pump light illumination a redistribution of electrons from the deep into the shallow levels occurs and as a result absorption is changed, because the absorption cross-section is different for the deep and the shallow traps. On the basis of these preliminary experimental results the Ru-doped BTO crystal is proposed as a promising material for near-infrared photorefractive applications.