Low power coherent grey soliton pair in photorefractive polymers

We theoretically show that low amplitude coherently coupled grey spatial soliton pairs can be observed in biased guest–host photorefractive polymers under steady-state conditions. These soliton pairs are predicted for the carrier beams sharing the same polarization, wavelength, and having a definite mutual phase difference. An exact solution for the grey soliton pair is obtained based on the coupled paraxial Helmholtz equation considering the nonlinearity of the photorefractive polymer. We investigate in detail the functional dependence of the coherently coupled soliton pair’s width with respect to two parameters, the beam intensity ratio and mutual phase difference for different external bias fields. We also find the existence of bistable states in this case.