Ferroelectric phenomena in holographic properties of strontium-barium niobate crystals doped with rare-earth elements

Abstract

We report on a relation between the two-beam coupling gain factor Gamma in Sr0.61Ba0.39Nb2O6 (SBN:0.6) crystals and their ferroelectric properties. In SBN:0.6 doped with rare-earth-metal impurities Ce and Tm we found a hysteresis dependence of Gamma versus the external de-field E applied after recording which is due to the ferroelectric P-E hysteresis. Particularly, Gamma-E hysteresis manifests itself in an alteration of the sign of Gamma, i.e., of the direction of the energy transfer between the coupling beams, under applying of E reversing Ps. The value of Gamma at room temperature essentially increases with impurity concentrations. It is caused by an increase of the dielectric permittivity, which in its turn is due to a significant lowering of the phase-transition temperature T-c produced by a rare-earth doping.