Stability of bright screening-photovoltaic spatial solitons

We present a theoretical analysis of the stability of screening-photovoltai c (SP) spatial solitons in biased photovoltaic-photorefractive materials in the case of neglecting the loss of the material and the effect of diffusio n. When an incident optical beam is a SP soliton, this beam propagates alon g a linear path with its shape kept unchanged. When the maximum amplitude, width and functional form of an incident optical beam are slightly differen t from those of a SP soliton, the beam reshapes itself and tries to evolve into a solitary wave after a short distance. That is, these SP solitons are stable against small perturbations. However, optical beams that significan tly differ from SP soliton solutions tend to experience larger cycles of co mpression and expansion, and their maximum amplitudes oscillate with propag ation distances. The larger the perturbations, the stronger the oscillation .