Quasistable bright dissipative holographic solitons in photorefractive two-wave mixing system

The dynamical evolution of both signal and pump beams are tracedby numerically solving the coupled-wave equation for aphotorefractive two-wave mixing system. The direct simulationsshow that, when the intensity ratio of the pump beam to thesignal beam is large enough, the pump beam presents a commondecaying behaviour without modulational instability (MI), whilethe signal beam can evolve into a quasistable spatial solitonwithin a regime in which the pump beam is depleted slightly. Thelarger the ratio is, the longer the regime is. Such quasistablesolitons can overcome the initial perturbations and numericalnoises in the course of propagation, perform several cycles ofslow oscillation in intensity and width, and persist over tensof diffraction lengths. From physical viewpoints, these solitonsactually exist as completely rigorous physical objects. If theratio is quite small, the pump beam is apt to show MI, duringwhich the signal beam experiences strong expansion and shrinkingin width and a drastic oscillation in intensity, or completelybreaks up. The simulations using actual experimental parametersdemonstrate that the observation of an effectively stablesoliton is quite possible in the proposed system.