Changes in the optical absorption induced in the Bi₁₂TiO₂₀:Al crystal by exposition to short- and long-wavelength radiation

The impurity absorption model is used to describe the experimentally observed reversible changes in the optical absorption spectrum induced in the Bi₁₂TiO₂₀:Al crystal by subsequent exposition to short-wavelength radiation with λ i , = 532 nm and longer-wavelength radiation with λ n changing from 588 to 1064 nm. The model takes into account the photoinduced transitions between two metastable states of a deep defect center leading to the change of its position in the crystal lattice under conditions of strong lattice relaxation. (paper)