Propagation Character For Intense Laser Beam In An Electron-positron-ion Plasma

The propagation of laser in a plasma plays an important role in fields of high harmonic generation,new light source,wake-field excitation and pulse compression,and it has attracted researcher's wide attentions.Recently,experimenters use the new equipment to produce electron-positron pairs.When the intense laser beam is propagating through the plasma,the emergence of electron-positron pairs can produce the electron positron ion(E-P-I)plasma.The special nature of the three-component plasma makes the interaction between intense laser beam and E-P-I plasma become a new research point.In this paper,we discuss the propagation characteristics of the laser beam in an inhomogeneous magnetized E-P-I plasma,the one-dimensional optical soliton and the stability of the intense laser.The main contents of this paper are organized as follows:In chapter 1,we introduce the research status,the basic knowledge of laser beam,plasma and the interaction between intense laser and plasma.Then the several nonlinear phenomena in the interaction between laser and plasma is further introduced in detail.In chapter 2,we study the propagation of the intense laser beam in an inhomogeneous magnetized electron-positron-ion(E-P-I)plasma.By considering the relativistic and the ponderomotive effects,we find the governing equations of the system reduce to a modified nonlinear Schr?dinger equation(NLSE),in which the magnetic field and the density inhomogeneous effects are included and we get the solitary wave solutions in one dimension of the equations.Then the modulation instability of the system is further discussed.Numerical results also show the nolinear interaction between laser beam and plasma can be enhanced with the strength of the external magnetic field,the density ratio increase of positrons to electrons and the inhomogeneity of the plasma density which also trigger other rich nonlinear phenomena.In chapter 3,the one-dimensional optical soliton and its stability of the intense laser beam in an homogeneous nonmagnetized E-P-I plasma are discussed.We solve the governing equations of a given system in one dimensional case.Firstly,we use the Sagdeev potential method to determine the existence of soliton solutions in the system and obtain the numerical solution of the laser vector potential in propagation.Secondly,the control equations of the system are approximated so that they can be expanded to form the generalized NLSE.Then we get an approximated solution of the laser vector potential during propagation.Finally,we analyze the stability of three solitary wave solutions which exist in the control equations of this physical system by using theoretical analysis and numerical methods.In chapter 4,we summarize the results of the paper.