激光脉冲在等离子体中的压缩分裂

通过数值求解一维非线性薛定谔方程，研究了圆偏振入射激光脉冲在初始密度范围为1/4到略低于1倍临界密度的等离子体中的自压缩和分裂现象. 提高等离子体密度和入射激光强度以及减小脉冲宽度可以在更短的传输距离获得有效的激光脉冲压缩，压缩后的脉冲半高宽度可达到初始脉冲半高宽度的1/35，甚至更小. 这种压缩是激光脉冲在等离子体中形成高阶孤子的过程中产生的，可以获得比在稀薄等离子体中更好的压缩比例. 数值计算的结果给出了该情况下激光脉冲在等离子体中自压缩后形成的高阶孤子分裂. 利用一维粒子数值模拟程序(particle-in-cell，PIC)也观察到了脉冲的压缩和分裂现象，得到了与数值计算一致的结果. 关键词：非线性薛定谔方程自压缩脉冲分裂粒子模拟

Self-compression and splitting of laser pulse in plasmas

We study the self-compression and splitting of a circularly polarized laser pulse propagating in plasmas with density window from 1/4 critical to slightly below critical density by solving the nonlinear Schrdinger equation numerically. It is demonstrated by the numerical calculation that the effective self-compression of laser pulse can be achieved in even shorter distance by increasing both the background plasma density and intensity of the laser pulse, or decreasing the width of pulse. The full-width at half maximum of the compressed pulse can reach 1/35 of the initial one's or even smaller. It has been found that this kind of self-compression occurs in the process of formation of a high-order soliton when a laser pulse propagates in a plasma, so that we can obtain greats compression ratio than in thin plasmas. We also obtained the splitting of a high-order soliton formed after self-compression of a laser pulse propagating in plasmas from the result of the numerical calculation in this situation. The phenomenon of self-compression and splitting is also observed by using one-dimensional particle-in-cell simulations and the result was consistent with the numerical calculation.