Spectral dependence of the photorefractive recording and erasure process in doped LiNbO3

Photocurrents responsible for the photorefractive recording sensitivity have been investigated in the absence and presence of external electrical fields in oxidized and partially reduced LiNbO3: Fe- and LiNbO3: Cu-crystals. Optical erasure and absorption have also been measured in the spectral range between 1.5 and 4.0 eV. The comparison of the spectra reveals the contributions of different centers and transitions to the photorefractive recording and erasure process and some details on the energy levels of transition metal centers in pyroelectric LiNbO3.