Photoinduced absorption in photorefractive crystals as result of long-living energy levels

We present investigations of the photoinduced absorption in photorefractive crystals BTO, SBN, BCT, and LiNbO3:Fe. We show and compare the experimental possibility of producing of long-living photoinduced absorption in these crystals. We explain the effect by the dynamic model of several long- and short-living levels. The methods of the absorption control are presented as well. They are based on successive periodical radiation on difference wavelengths. The methods can be explained by the dynamic model, which was developed and numerically confirmed starting from the experimental temporal behaviour of the effect. Cw-radiation (514nm, 532nm, 633nm) and pulse radiation (532, 355nm) are used for inducing and controlling of the absorption.