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In this paper, we report experimental results on laser beam guiding by a self-tightening lattice photo induced in a strontium barium niobate (SBN) photorefractive crystal. In such setting, optical lattice (or periodical array of strongly-coupled waveguides) gradually transforms into array of weakly coupled ones. Experimental data are supported by computer simulation, which revealed crucial role of induced modulation instability in the strong laser beam guiding.

Experimental evidence of the cnoidal waves self-compression in photorefractive BTO crystal with drift nonlinearity is reported. The self-compression processes for a high voltages are limited by development of dynamic instability. Experimental data are supported by computer simulation.

We present experimental and theoretical results, which support the hypothesis that the photoinduced scattering in iron-doped lithium niobate crystals is due to the permanent amplification of nonstationary noise. The experiments that we present contradict the earlier suggested theory, which explains the noise as a three-wave mixing amplification process.

Two-wave mixing with a small angle between beams in a photorefractive crystal biased with an external electric field leads to the formation of additional non-Bragg orders and to wave amplification. A steady-state gain of 25 cm (-1) was obtained for an external voltage of 3 kV/cm in strontium barium niobate. Noise amplification and oscillation are also demonstrated.

We discuss a phase synthetic hologram, for encoding arbitrary complex fields, whose design is based on a sinusoidal phase grating with a spatially modulated phase depth. An important feature of the hologram is that it encodes the complex field at the zero diffraction order of the carrier grating. The smoothness of this sinusoidal carrier grating facilitates the implementation of the hologram with a pixelated spatial light modulator. We take advantage of the hologram reconstruction at the zero-diffraction order for the simultaneous generation of a collection of complex beams.

Interference fringes produced by the intersection of two plane waves in photorefractive strontium barium niobate crystal break in the transverse direction if the external electric field is high enough. For a certain relation between fringe spacing and nonlinearity strength, the tendency to regular pattern formation has been observed. We present a simple theory that qualitatively explains this effect.

We investigate theoretically the interaction of two or more beams intersecting at a small angle in a photorefractive crystal with a local type of holographic recording. All necessary diffraction orders are taken into account. It is shown that for photorefractive ferroelectrics the number of diffracted beams can be quite large. For negative nonlinearlity the high exponential gain previously predicted for three- or four-wave mixing does not exist if all diffraction orders are considered.