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The reflectivity and time response of self-pumped phase conjugators using ii Cu-doped potassium sodium barium strontium niobiate (KNSBN:Cu) crystal in both internal and external geometries are investigated. The light source used is an Ar+ laser operating at 514.5 run, It was observed that the reflectivity remains constant at low power and begins to drop above a certain threshold power in both phase conjugators, and the response time of the internal phase conjugator increases with power, it was shown with two-beam coupling measurements that some of the observed phenomena result from a drop in the codirectional and contradirectional two-beam coupling gain coefficients of the crystal above a threshold intensity of 43 W cm-2. (C) 1998 Elsevier Science B.V.

The influence of four sets of multiple reflection waves from self-pumped phase conjugators with doped (K0.5Na0.5)0.2(Sr0.75Ba0.25)0.9Nb2O6 photorefractive crystals on the conjugation fidelity is analyzed in presence of pyroelectric effect and photovoltaic effect. Some proposals to improve the conjugation fidelity of a self-pumped phase conjugator are demonstrated. The multiple reflection waves and their dynamic features are observed and analyzed.

The internal self-generated loop in a photorefractive Cu-doped KNSBN crystal and the nehavior of phase-conjugate beams during self-pumping have been studied experimentally. Their relations to the crystal's coupling constant, dimension and experimental conditions were analyzed.