Linearity and Non-linearity of Photorefractive effect in Materials using the Band transport Model.
In this paper we have studied the Linearity and Non-linearity of Photorefractive effect in materials using the band transport model. For low light beam intensities the change in the refractive index is proportional to the electric field for linear optics while for non- linear optics the change in refractive index is directly proportional to the square of the electric field. From our studies, it can be seen that the diffusion field is inversely proportional to period of interference pattern while the space charge field is directly proportional to the period of interference pattern. In the absence of the external electric field the space-charge field is spatially phase shifted by π/2 relative to the interference fringe pattern, which plays a key role in the energy exchange in two-wave mixing. In the presence of the external electric field the scaling factor is a complex quantity indicating that the externally applied electric field does not only change the magnitude of the space-charge field but also alters its spatial phase.