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A femtosecond-laser interaction experiment with a high laser intensity of TW/cm2 that is close to the optical breakdown threshold for dielectrics is performed.The high intensity results in fast excitation of large number of free carriers (1020-1021cm-3) followed by the diffusion, recombination and re-trapping of charges. These effects are responsible for the short time of the build-up of the electric field of charge separation and for the high rate of refractive index change. The amplitude of laser electric field at TW/cm2 intensity constitutes 27.46 MV/cm that is two orders of magnitude larger than the photovoltaic field or the field of spontaneous polarisation in ferroelectrics. The amplitude of the electrons oscillations in such a field is ~2-3 times larger then shift of Li (0.9 A) and Nb (0.5 A) responsible for spontaneous polarisation in LiNbO3. Therefore the predominance of the photovoltaic effect and even survival of the ferroelectric state under such perturbation is questionable and is the subject of discussion.