LIGHT-INDUCED CHARGE-TRANSPORT PROCESSES IN PHOTOREFRACTIVE CRYSTALS .1. MODELS AND EXPERIMENTAL METHODS

Light-induced charge transport processes are essential for photorefrac tive effects in electrooptic crystals. Charge driving forces, charge t ransport models and experimental methods for investigation of charge t ransport processes are reviewed. - Drift, bulk photovoltaic currents a nd diffusion are the charge driving forces. The one-center model witho ut and with electron-hole competition and two-level models, i.e., the two-center model and the three-valence model, are described. The speci al features of the different models in the case of homogeneous and inh omogeneous illumination are pointed out. Methods for reliable measurem ents of absorption, light induced absorption changes, dark and photoco nductivities, amplitude and phase of refractive index and absorption g ratings, and of charge carrier mobilities are presented.