Coherently coupled spatial soliton pairs in biased photorefractive crystals with both the linear and quadratic electro-optic effects

A study of coherently coupled spatial soliton pair propagating along the same line in biased photorefractive crystals where the changes of refractive index are governed by both the linear and quadratic electro-optic effects simultaneously is presented. It is shown that coherently coupled bright–bright, dark–dark and gray–gray spatial soliton pairs can be supported in steady-state regime under appropriate conditions. Moreover, the effects of three physical factors, i.e., the intensity ratio and the initial phase difference between two incident coherent beams, and various external bias field on the existence conditions, properties of these coherently coupled soliton pairs have been discussed in detail.