A new physical effect is reported. In single crystals of lithium niobate (LiNbO3), we have observed an acoustical memory effect. An acoustical tone burst is stored inside the crystal and reemitted at a later time. This memory signal is related to the acousto-electrical properties of the ferroelectric medium. Futhermore, it is shown to be sensitive to both temperature and frequency.

The radiation-induced optical absorption in ionic crystals is remarkably removed by a room-temperature ultrasonic treatment of the crystals. It is shown that the effect can be explained by defect migration processes occurring in ultrasonic fields. The experimental results display features consistent with a recent theory of the quantum diffusion. This new method of a cold annealing of radiation defects in solids can be termed as ultrasonic defect manipulation.

Application of the second harmonic generation microscope to nondestructive observation of periodically poled ferroelectric domains in quasi-phase-matched wavelength converters A two-dimensional periodically poled ferroelectric resonator is reported. The theoretical calculations, computer simulations by the finite element method and experimental data from the lithium tantalite samples reveal a domain acoustoelectric resonance. A polarization inversion in a y-rotated cut of a ferroelectric chip is done. A distribution of an electric potential over crystal surface may be an effective experimental tool for characterization of the periodically poled ferroelectrics.

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