Temporal fluctuation in photorefractive wave mixing

We analyzed the physical origin of the temporal fluctuation of the photoref ractive space-charge field, and found that fluctuation mainly results from fluctuations in the free-charge-carrier density which is, in turn, due to t he very small fluctuations of the input total intensity and the thermal exc itation. We studied the influence of various externally-controlled paramete rs such as the grating wave vector, the applied electric field, and the mov ing velocity of the grating on the fluctuation of the photorefractive space -charge field. We present experimental results for temporal fluctuations in photorefractive BaTiO3: Ce two-wave mixing and in BaTiO3 cat self-pumped p hase conjugation. The experimental results show agreement with the theoreti cal result.