激光与线性递增等离子体作用的非线性过程研究

利用四阶Runge-Kutta法进行数值求解,研究了密度梯度尺度、等离子体初始密度和激光强度对强激光与密度线性递增等离子体的自聚焦效应的影响。研究表明:密度梯度尺度越小,束腰宽度受相对论自聚焦的影响越大,又由于等离子体密度的线性递增分布,峰值会逐渐减小;密度线性递增,相对论自聚焦的效果越明显,之后束腰宽度峰值会由于不均匀密度项的影响而逐渐减小;随着激光强度的增大,在密度线性递增等离子体中,衍射作用越明显,越不利于自聚焦的产生。所得结果对强激光与线性递增等离子体产生自聚焦方案具有理论指导意义。

The Analysis of the Nonlinear Process of Laser in the Linear Increasing Plasma

The influences that the density gradient scale, initial density of plasma and intensity of la- ser have up on the injection of intense laser in linear up-ramp density of plasma are studied by using four order Runge-Kutta method. It is found that the lower the density gradient scale is, the lager the relativistic self-focusing is. And the linear up-ramp density profile results in the decreasing of spot size peak. Relativistic self-focusing of up-ramp density is better than uniform density profile, and after that peak of the spot size decreases due to the plasma inhomogeneity. In the plasma with the linear up-ramp density profile, the lager the intensity of the laser is, the more obvious the diffraction is, i. e. , the worse the self-focusing is. The results may be significant theoretically to the mechanism of self-focusing of intense laser in the linear up-ramp density of plasma.