Universal Theory Of Steady State Optical Spatial Solitons In Photorefractive Media

Based on the universal theory of one-dimensional steady state photorefractive solitons, this paper describes all kinds of one-dimensional steady state spatial solitons in the photorefractive or photovoltaic-photorefractive medium with or without a resistor in the external circuit. The steady-state solutions of the evolution equation are given and then the physical properties of the photorefractive solitons are discussed. By solving the equation numerically, the effects of diffusion on the property of the self-deflection of the photorefractive solitons are studied. The results show that the spatial shifts of bright screening solitons and SP solitons depend directly on the voltage factor. For dark solitons, the stronger the input intensity is, the larger the bending-angle is, whereas bright solitons depend on the input intensity nonlinearly. The effects of the higher-order terms on the self-deflection process of photorefractive bright solitons in a crystal are also investigated. Compared the results of first-order diffusion term acting alone with both the first-order diffusion term and the higher-order space charge field terms acting together, the screening solitons always bend right, whereas for the self-deflection of the photovoltaic bright solitons and the screening-photovoltaic bright solitons both bending right or left is possible, and it is possible that no self-deflection process occurs. Finally modulation of solitary evolution of Gaussian beams is discussed, and the results show that changing the load resistance can make a Gaussian beam evolve into a stable bright soliton when propagating in a biased photovoltaic-photorefractive crystal.