Light-induced charge transport processes in photorefractive crystals .1. Models and experimental methods

Light-induced charge transport processes are essential for photorefractive effects in electrooptic crystals. Charge driving forces, charge transport models and experimental methods for investigation of charge transport processes are reviewed. - Drift, bulk photovoltaic currents and diffusion are the charge driving forces. The one-center model without and with electron-hole competition and two-level models, i.e., the two-center model and the three-valence model, are described. The special features of the different models in the case of homogeneous and inhomogeneous illumination are pointed out. Methods for reliable measurements of absorption, light induced absorption changes, dark and photoconductivities, amplitude and phase of refractive index and absorption gratings, and of charge carrier mobilities are presented.