We report a theoretical. model for a photorefractive running hologram in bulk-absorbing materials in the presence of self-diffraction and use this model to analyze experiments for photorefractive materials characterization. A nonperturbative technique that allows one to measure at the same time the diffraction efficiency and the output beam's phase shift is reported, and its advantages are discussed. We use this technique and apply the theoretical model to compute some parameters for the electron-charge carriers (Debye screening length l(s) approximate to 0.03 mum, diffusion length L-D approximate to 0.14 mum, and photoexcitation quantum efficiency Phi approximate to 0.45) at the 514.5 nm-wavelength laser line for a nominally undoped Bi12TiO20 crystal. Particular experimental features are detected and assumed to be consequences of hole-electron competition in this sample. (C) 2001 Optical Society of America.183291297