Bright photorefractive solitons supported by simultaneous linear and quadratic electro-optic effect with both drift and diffusion charge transport

We have predicted a new and large family of optical spatial solitons in photorefractive crystals having both linear and quadratic electro-optic effects by considering for the first time an equal significance of both drift and diffusion on the charge transport. We solve the ensuing modified Nonlinear Schrödinger equation employing the paraxial approximation in conjunction with a variational solution. Consequently, we have derived the existence curve of solitons together with the evolution equations for soliton width and deflection. Bistable states have been found, revealing two threshold powers for soliton generation associated with a certain soliton width. Distinct power regimes have been identified on this basis, and the evolution of soliton breadth and self-deflection has been examined within these contexts. The external electric field affects the soliton trajectory, with self-deflection escalating as the electric field intensifies. The interaction between the linear and quadratic electro-optic effects has been examined by analyzing two scenarios: one in which the linear electro-optic effect predominates, and another in which the quadratic effect prevails. We analyze and differentiate the impact of each electro-optic effect on the existence curve of solitons and their trajectories.