The interference pattern of light waves creates a refractive index modulation in photorefractive media. This process is relatively well described by the theory (Kukhtarev equations) but deviations are found. Therefore, experimental methods are used in order to characterize the processes. The influence of the absolute intensity as well as of the intensity ratio of the interfering waves on the refractive index modulation are studied in a two-wave mixing arrangement. Especially for the dependence on the absolute intensity the interesting relation Δn = f(I_(abs)) ∝ I_(abs)~α was found that is not predicted by the theory. Nevertheless, this experimental approximation can be used in calculation in order to minimize the error. For a four-wave mixing arrangement working as a phase conjugate mirror, the time development of the reflectivity after switching on the reading pump wave is investigated. It will be shown that always for a short time high reflectivities can be reached. For suitable intensity ratios of the interacting waves this is also possible in the steady state. This behavior will be explained theoretically. A better understanding of the grating buildup processes is reached by these studies, which allow the specific controlling of interaction parameters of the wave mixing.
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