Photovoltaic instabilities

Abstract A review of recently discovered instability phenomena related to the photovoltaic current is presented. It includes the photo-electric domain instability observed in ruby crystals and the instability causing excitation trap recharging waves in photorefractive crystals. The photoelectric instability leading to formation of stationary domain structure is due to an absolute negative photoconductivity of the crystal in zero electric field. It is shown that such instability should occur in some ferroelectrics e.g. in KDP crystals. The spontaneous excitation of trap recharging waves in uniformly illuminated noncentrosymmetric crystals is induced by the photovoltaic current which becomes inhomogeneous in the presence of such waves. Effects related to trap recharging waves in photorefractive crystals, namely beam coupling, space charge stratification and stimulated light scattering are discussed. These effects are important for dynamic holography.

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