Temporal Analysis Of Photovoltaic Spatial Solitons In Two-photon Photorefractive Materials

Photorefractive spatial solitons has been a hot topic in nonlinear optics. All the previous researches of the photorefractive spatial result from the single-photon photorefractive effect. In 2003, Castro-Camus et al. proposed a model of two-photon photorefractive effect which was called the Castro-Camus model. The model with an intermediate allowed level is different from the single photon model, intermediate allowed level is used maintain a quantity of excited electrons from the valence band by signal beam. We theoretically study the temporal behavior of two-photon photorefractive photovoltaic spatial solitons based on Castro-Camus model in this paper.In two-photon photorefractive material of photovoltaic effect is obtained from two-photon photorefractive model. On this basis, according to the boundary conditions of open-circuit and closed-circuit, respectively expressions for time-dependent space charge field are obtained.For temporal behavior of open-circuit photovoltaic spatial solitons, we derive a time-dependent propagation equation of dark and bright soliton under open-circuit conditions, and then discuss its intensity profile at different times. Finally, taking into account the low amplitude of incident light, we investigate the temporal behavior of dark and bright two-photon photorefractive photovoltaic spatial soliton in the circumstances of low-amplitude and open-circuit conditions.We give the time-dependent propagation equation of dark and bright soliton under closed-circuit conditions. and then discuss its intensity profile at different times by the numerical method. As current density exists in the closed-circuit conditions, we consider the changes of soliton intensity FWHM at different values of current density.