ON STRUCTURAL DAMAGES INDUCED IN PHOTOREFRACTIVE PROCESSES IN LINBO3-FE CRYSTALS

The temporal characteristics of the photorefractive diffraction effici ency were measured on LiNbO3:Fe single crystal samples using a cw Argo n-ion laser with power density of 1.5 W cm(-2). During successive writ ing-erasure cycles systematic changes were recorded in the time charac teristics with increasing irradiation dose up to 3.2 x 10(4) J cm(-2). Though the used power density was much lower than the known pulse-las er induced damage threshold values (0.1-11 GW cm(-2)), over a critical dose of about 1.5 x 10(4) J cm(-2) definite structural damages of sam ples could be observed by light- and scanning electron microscopy. The dose-dependent changes observed in the diffraction efficiency and the simultaneous cumulative structural damages are firstly described.