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The dynamic evolution of bright spatial solitons induced by the transverse shifting of the beam is investigated. Transverse shifting can result in the formation and dynamic evolution of bright spatial solitons in photorefractive materials. To explain the phenomena, a uniform theoretical physical model is proposed. Numerical analysis results show that the beam shifting has strong influence on the formation and dynamic evolution of bright spatial solitons.

Measurements for photorefractive dynamic properties under polarized light with different luminous intensity and wavelength at 650 nm were performed in calcium-doped strontium barium niobate crystals as a function of the time. Experimental results further validated that the different input luminous intensities influence only the saturated time and photorefractive velocity of the photorefractive crystals. Birefringence experiments suggest that an input luminous intensity oscillatory threshold should exist between 64 mW/cm^2 and 13 mW/cm^2. The dynamic change of refractive index from self-focusing to asymmetric self-defocusing was also measured and regarded as the mutual results of the nonuniform-intensity incidence and positive thermal lens effect, which was validated by a further experiment based on the Michelson interference. Also, oscillation accompanying change in the dynamic indices was analyzed and attributed to the high dielectric effect as well as asymmetric self-defocusing in this investigation.

We observe spatial bright solitons in a transversely shifting LiNbO_3 crystal. In this scheme, the photovoltaic nonlinearity in LiNbO_3 can be switched from self-defocusing to self-focusing by continuous shifting of the beam. Moreover, the shifting velocity has a strong influence on the wave shape of the bright spatial solitons.