Photorefractive properties of lithium niobate crystals studied by Raman spectroscopy

Time evolution of Raman spectra depending on temperature were carried out on iron-doped photorefractive lithium niobate crystals with different Li content in the melt. The frequency shift of Raman lines are observed with time giving the possibility to calculate the saturation values of the photorefractive space charge field showing a linear decrease with temperature. Space charge field values are much lower for near-stoichiometric compsition sample comparing to near-congruent ones.