Manakov solitons in biased photorefractive crystals with both the linear and quadratic electro-optic effect

It is shown theoretically that the dark–dark, bright–bright and dark–bright Manakov soliton pairs can exist in biased photorefractive materials with both the linear and quadratic electro-optic effect under steady-state conditions. These soliton pairs can be generated provided that the total intensity of the two mutually inherent, with the same wavelength optical beams is much lower than the sum of the background intensity and the dark irradiance. It is also found that the intensity full width at half maximum of these Manakov solitons is inversely proportional to the square root of a quadratic polynomial of the external bias field. Moreover, the linear and quadratic electro-optic effects can be enhanced, decreased, even offset under appropriate conditions.