Ishikawa Kenichi, Kumagai Hiroshi, Midorikawa Katsumi
Department of Quantum Engineering and Systems Science, Graduate School of Engineering, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-8656, Japan.
Phys Rev E Stat Nonlin Soft Matter Phys. 2002 Nov;66(5 Pt 2):056608. doi: 10.1103/PhysRevE.66.056608. Epub 2002 Nov 21.
We present a numerical study of the (2+1)-dimensional propagation dynamics of femtosecond-laser pulses in silica. In particular, considered are pulses, whose power is tens to hundreds of times higher than the threshold for self-focusing. We solve the axially symmetric, extended, nonlinear Schrödinger equation for the laser electric field, including group velocity dispersion, Kerr nonlinearity, plasma formation and defocusing, self-steepening, and space-time focusing. Our simulation results reveal that the high-power pulses are split spatially, as well as temporally, several times into multiple cones during its propagation. This new structure is formed as a result of the interplay of strong Kerr self-focusing and plasma defocusing. The number of cones and their angle with respect to the propagation axis increase with incident pulse energy. The uncertainty, which may be contained in the evaluation of plasma response and band-to-band transition rate, and the pulse disturbance by modulation instability are also analyzed. Although these influence the details of the pulse propagation, they do not affect the essence of our results: the multiple-cone formation.
我们对飞秒激光脉冲在二氧化硅中的(2 + 1)维传播动力学进行了数值研究。特别地，所考虑的脉冲功率比自聚焦阈值高数十到数百倍。我们求解了激光电场的轴对称、扩展的非线性薛定谔方程，其中包括群速度色散、克尔非线性、等离子体形成与散焦、自陡峭以及时空聚焦。我们的模拟结果表明，高功率脉冲在传播过程中会在空间和时间上多次分裂成多个圆锥体。这种新结构是强克尔自聚焦和等离子体散焦相互作用的结果。圆锥体的数量及其相对于传播轴的角度随入射脉冲能量增加。还分析了等离子体响应和带间跃迁率评估中可能存在的不确定性以及调制不稳定性引起的脉冲扰动。尽管这些会影响脉冲传播的细节，但它们并不影响我们结果的本质：多圆锥体的形成。
