Abstract
We show that incoherently coupled soliton pairs are possible in biased photorefractive crystals, under steady-state conditions. These solitons can propagate in bright-bright, dark-dark, as well as in bright-dark configurations. Such soliton pairs can be established provided that the carrier beams share the same polarization, wavelength, and are mutually incoherent. Relevant examples are provided where the photorefractive crystal is of the strontium barium niobate type. The characteristics and stability properties of these soliton states are also discussed in detail. (C) 1996 American Institute of Physics.

Abstract
We investigate higher-order space charge field effects on the evolution of bright spatial solitons in biased photorefractive crystals under steady-state conditions. Numerical simulations demonstrate that these optical solitons can experience considerable increase in their self-deflection especially in the regime of very high bias field strengths. This process is further studied using perturbation techniques. Our analysis indicates, that for very high bias fields, the self-bending process is further enhanced by a factor that varies cubically with the applied field. Relevant examples are provided.

Abstract
Summary form only given. Shock waves have been extensively investigated in diverse areas of physics. However, their occurrence in optics is rather rare and thus far no such optical structures have been experimentally observed. In this paper we report a new family of kink-antikink shock waves that is possible in unbiased photorefactive media via the two wave mixing process. These waves move together as locked states, and have the interesting property of moving outside their initial ±? sector of propagation. The apparent direction of propagation and the spatial widths of these shock wave beams are directly related to their relative intensity. We provide a detailed analysis of these waves, and we illustrate their behavior with pertinent examples. © 2001 Optical Soc. Of America.

Abstract

Abstract
We report the first experimental observation of optical spatial shock-wave pairs. The shock waves consist of two coupled kink and antikink beams that remain locked to each other throughout propagation in a nonlinear diffusion-driven photorefractive crystal. These coupled shock-wave pairs move undistorted at angles that fall outside their original angular sector of propagation.

Abstract
We investigate the coherence characteristics of multimode incoherent spatial solitons in noninstantaneous Kerr-like nonlinear media. Other properties of these incoherent solitons are also discussed as a function of their modal composition. [S1063-651X(99)04001-5].