Investigation of photo-induced absorption in a Bi12TiO20 crystal

ABSTRACT A photorefractive Bi12TiO20 (BTO) crystal is exposed with high intensity pulsed-laser beams 532 nm (the average intensity of the laser was 110mW/cm2, the average intensity per pulse was 2MW/cm2), and the photo-induced dynamics of the absorption between 480 and 900 nm are studied and explained by two long-lived energy levels in the forbidden band. The relaxation times of the long-lived energy levels are experimentally found to be 104 and 105 s. The hysteresis character of the absorption coefficient is discussed. PACS 42.70.Mp; 42.70.G