Study On Self-focusing Of Laser Pulse Propagating In Underdense Plasma

Propagation of intense laser pulse in cold underdense plasma is an important aspect in studying laser target. The refractive index of plasma media becomes related with the laser pulse intensity because of the appearance of nonlinear effects when propagation and makes the light path changed so that the modification instability may be leaded out to the phenomenon of self-focusing.When the intensity of laser pulse propagating becomes stronger, the ponderomotive force will also get stronger. The embroil part, which is one of the sources of ponderomotive force, will get stronger, too, and can't be neglected. We bring into embroil part on the base of previous works to make the ponderomotive force full, and giving that the laser pulse is so intense that the quiver velocity of electrons reach the speed of light, the relativistic effect will be considered here. That's the first work of this paper.And then, we thought of that many of the basic particle actions in plasma are most related with external field. If we bring outside magnetic field into plasma, the actions of particles will move more complex, and so is the actions between laser pulse and plasma which may influence the self-focusing. In previous works of other people, the self-focusing in magnetized plasma with a outside magnetic field in special aspect have been studied, so the next work of this paper is to study the influence to self-focusing by non-special aspect outside magnetic field, meanwhile the influence by different intensity of outside magnetic field to self-focusing has also been got.