Study On Photovoltaic Solitons In Photorefractive Media With Both The Linear And Quadratic Electro-Optic Effects

The photorefractive spatial optical solitons will be formed with milliwatts or microwatts of magnitude of light intensity. People have been studied on photorefractive spatial solitons based on the linear electro-optic effect or the quadratic electro-optic effect solely. In this paper, photovoltaic(PV) solitons based on both the linear and quadratic electro-optic effect will be presented firstly.The space charge field in the photovoltaic photorefractive media will be derived with the circuit closed, on the base of the band transport model of the photorefractive media. Then the non-linear changes of refractive index in the photorefractive(PR) materials are governed by both the linear and quadratic electro-optic(EO) effects simultaneously. The evolution equations of the incident beam in the PR materials will be presented. Then the bright, dark, and gray spatial soliton solutions of the evolution equations will be obtained on the basis of the boundary conditions, ignoring the diffusion effect. The formation of the photovoltaic solitons in the photovoltaic-photorefractive materials such as lithium niobate crystals will be simulated. And the influence of the PV filed on the formation of the soliton are discussed.The beam propagation equation in PV media will is established under open-circuit conditions with reference to the formation of solitons under closed-circuit conditions. Then the bright, dark solitons and the formation conditions will be gived. We obtained that the strength of the PV field and strength of the quadratic electro-optic effect will impact the formation of solitons. The analytical solutions in the low-amplitude regime are also obtained.The self-deflection of the bright spatial solitons will occur in consideration of diffusion effect. The beam propagation will be investigated symmetrically considering the diffusion effect both in open-circuit and closed-circuit by the use of numerical techniques and perturbation methods. The relationship between the PV filed and the horizontal offset of the beam center will be discussed.