Research On The Evolution And Self-deflection Property Of Screening-photovoltaic Spatial Optical Solitons

Spatial optical solitons in photorefractive media attracted much interest in the past few years. At present, threes of scalar solitons (quasi-steady-state, screening and photovoltaic solitons) have been predicted and found. So far, photovoltaic solitons and screening solitons are studied individually. On the other hand, our recent theoretical work predicted that one other type of photorefractive solitons, namely screening-photovoltaic (SP) solitons, was possible under steady-state condition in biased photovoltaic-photorefractive crystals. In particular, we can think of SP solitons as the biased photovoltaic solitons. Allowing an external field is to allow a large nonlinearity and hence narrower solitons than the photovoltaic field or the screening field alone. These SP solitons result from both the photovoltaic effect and spatially nonuniform screening of the applied field differ from their previously observed steady state spatial solitons in terms of their properties and experimental conditions. In a given physical system, the shape and width of these SP solitons is uniquely determined by the magnitude and polarity and their peak intensity to that of the dark irradiance. We can think of SP solitons as the unity form of screening and closed-circuit photovoltaic solitons. If the bias field is much stronger than photovoltaic field, the SP solitons are just like the screening solitons. If the applied field is absence, the SP solitons degenerate into the photovoltaic solitons in the closed circuit condition. In other words, whether the closed-circuit photovoltaic soliton or screening soliton is the special case of the SP soliton. Therefore, the corresponding results about screening and photovoltaic soliton are obtained from our results about SP solitons by taking the value of photovoltaic field and external bias field as zero, respectively. The paper is divided into 9 chapters. Chapter 1 gives the present situation of the studies of solitons. The main results got in this dissertation are also summarized here. Chapter 2 gives the fundamental theory of solitons and the approach of how to solve the solitary equations. Chapter 3 summarizes the numrical method for solving nonlinear equations. Chapter 4 studies the properties of SP spatial solitons within the crystal. Chapter 5 studies the dynamical evolution of bright SP spatial solitons. Chapter 6 studies the dynamical evolution of dark SP spatial solitons. Chapter 7 studies the impact of the loss on the solitarily evolution of a SP spatial soliton in the crystal. In chapter 8, the self-deflection of the solitarily evolution of a SP bright spatial soliton in the crystal is discussed. In chapter 9, the solitarily evolution and self-deflection of a Gaussian beam in the biased photovoltaic-photorefractive crystals is studied, the impact of the loss on the solitarily evolution of it in the crystal is also studied in this chapter.