Theoretical Investigation Of Ultrashort Intense Laser Propagation In Plasma Channel

In the thesis, the propagation of the ultrashort intense laser beam in the plasma channel was investigated theoretically. The thesis analyzed the effects, associated with the propagation of laser in plasma channel, such as diffraction, plasma defocusing, the third-order intensity-dependent nonlinearity, the relativistic self-focusing, the focusing and defocusing of the plasma channel, and the absorbtion in the collision plasma and the finite pulse length effect. The thesis is composed of 4 chapters, among which are, Chapter 1 is a survey, Chapter 2, 3 are the introductions of our own work, Chapter 4 is a conclusion and prospect.Chapter 1: The background of the study of propagation of ultrashort intense laser in plasma channel and a survey of the interaction of laser with plasma were introduced.Chapter 2: Characteristics of propagation of ultra-intense laser beam in a partially stripped preformed plasma channel is discussed, in which the relativistic self-focusing effects, together with the perturbed plasma density, is discussed. From Maxwell equations the refractive index equation and Hamilton-Jacobi equation, which describe the evolution of the electric field, are derived including the effects of the diffraction, the third-order intensity-dependent nonlinearity, plasma defocusing, the focusing and defocusing of the plasma channel, and the relativistic self-focusing. The envelope equation of laser propagating in the plasma channel, and the general expression related the laser spot size with the propagation distance and the width of the plasma channel etc., are derived based onthe Hamilton-Jacobi equation and the refractive index equation.Chapter 3: The source-dependent expansion (SDE) method for analyzing the waveequation is introduced, which is an effective method for solving the paraxial wave equation with nonlinear source terms. Two examples have been given to explain this method, which are the propagation of the ultrashort intense laser pulses propagation in the partially stripped plasma in which the collisions of plasma electrons are taken into account, and the propagation including the finite pulse length effect. The solutions are derived through SDE method introduced in the chapter, which are four differential equations of the electric field parameters, i.e., the wave curvature as, the spot size rs, the laser power p and the phase s.Chapter 4: There are a summary of two methods used in this thesis, together withthe further work, a introduction of Vlasov equation and its moment equations, i.e., thecontinuity equation, the force equation and the pressure equation, and the ionization andrecombination associated with the laser propagation in media.