Nonlinear response of photorefractive lithium tantalate and niobate at acoustic frequencies

An amplification of the intensity of pump oscillations is observed experimentally at frequencies from 100 Hz to 1 kHz during photoinduced light scattering and holographic-type parametric scattering in photorefractive lithium tantalate and niobate. Possible ways are analyzed for explaining the existence of a photorefractive response in these crystals over times of 10⁻²–10⁻³ s, which are five orders of magnitude shorter than the Maxwell time. Zh. éksp. Teor. Fiz. 112, 1490–1498 (October 1997)