Theoretical Study On Properties Of Beams Propagating In Photovoltaic-photorefractive Crystals

Screening-photovoltaic (SP) spatial soliton is a new type of photorefractive spatialsoliton that has been proved theoretically recently. It is formed in biased photovoltaic-photorefractive crystals and results from both non-uniform spatial screening of thebiased field and photovoltaic effect. Based on the physical process of thephotorefractive effect, the evolution of the optical beam propagating in photorefractivecrystals is derived with the consideration of both the drift and photovoltaic mechanism.The steady-state solutions of the evolution equation with the form of SP solitons aregiven and then the physical properties of the SP solitons are discussed. By using a kindof SP soliton or Gaussian beam as an input beam into the photorefractive crystal and bysolving the equation numerically, the dynamical properties of evolution and self-deflection of the input beam are investigated. In the end, the effects of loss on theproperty of the input beam are studied. The results show that when the input beam is aSP solitary wave or a matched Gaussian beam, it can propagate with its profileunchanged in the crystal. If the intensity profile of the input beam is slightly differentfrom that of the SP soliton supported by the crystal with the same parameters, it canevolve into a SP solitary wave after a certain distance of propagating. If the input beamdeviates from the SP soliton supported by the crystal significantly, it cannot propagatestably in the crystal. The diffusion effect can cause the center of the beam move on aparabolic trajectory and the loss effect causes the intensity of the beam attenuateexponentially.