Formation of Photorefractive Solitons

Abstract

A theory for time dependence and formation of optical spatial solitons in photorefractive crystals has been discussed. The temporal evolution of the induced space charge field is studied and hence the dynamical evolution equation with an explicit temporal dependence is derived. A general theory for incorporating the temporal characteristics in the theoretical formulation for photorefractive solitons is then discussed. This theory is illustrated to be valid for different types and configurations of photorefractive crystals. The ratio of the maximum intensity to the dark irradiance of the incident beam profoundly affects the temporal characteristics and hence the temporal development of the soliton width has been studied as a function of the intensity ratio. The relevant conditions for formation of steady state and quasi steady state solitons are studied. The intensity dependence on the soliton width at initial time and the soliton width at steady state is studied. The magnitude of the electro-optic coefficients affect the temporal evolution of solitons which has been discussed. We then discuss how this theory can be reduced to study the temporal evolution of screening solitons and centrosymmetric solitons. Finally, the theory for temporal evolution of solitons in biased photovoltaic photorefractive crystals is considered. The response time can be controlled by the value of current density. The time dependent space charge field is derived and the requisite time evolution of photovoltaic solitons is investigated. A further reduction of this theory for screening solitons and photovoltaic solitons is briefly commented upon.