附加稳恒磁场对高次谐波产生过程的影响
The effect of the additional static magnetic field onthe high-order harmonic generation process
AbstractI n this paper, we study the high-order harmonic generation process in theexternal field composed by a strong laser field and an additional static magnetic field.The pseudo-spectral split-operator method is used to solve the time-dependentSchrodinger equation; and the high order harmonic spectra are obtained by the theFourier transform of the time-dependent electric dipole moment. Our numericalresults show that when the magnetic field is weak (B=0.01a.u.), its effect can beneglected; with the increase of the magnetic field intensity (B=0.05a.u.), theharmonic cut-off frequency show a significant extension; a further enhancement ofthe magnetic intensity (B=0.10a.u.), can induce not only a further extension of theharmonic spectrum, but also an enhancement of the harmonic intensity; however,when the magnetic field is even stronger (B=0.20a.u.), the cut-off frequency can notbe further extended. We analyzed the electron’s survival probability at the groundstate in the laser pulse, and attributed the effect of the static magnetic field to twofactors: (1) magnetic barrier which prevents the electron ionization; (2) Lorentz forcewhich increases the re-collision probability of the ionized electron. The high orderharmonic spectra for different magnetic induction intensities of the additionalmagnetic field can be well understood.
Key words: static magnetic field high-order harmonic Split-operator method
目录
摘要Ⅰ
AbstractⅡ
目录Ⅲ
图清单-Ⅳ
表清单-Ⅳ
1绪论-1
1.1在强激光下与物质作用的研究-1
1.2原子在激光场中的电离-2
1.2.1多光子电离和阈上电离3
1.2.2随穿电离和过势垒电离-4
1.3高次谐波谱5
1.3.1高次谐波发射理论解释6
1.3.2高次谐波问题的研究意义7
2理论基础-9
2.1原子在激光场中的含时薛定谔方程-9
2.2拟谱法求解定态薛定谔方程9
2.3分裂算符法对波函数的时间演化11
2.3.1分裂算符法12
2.3.2波函数的时间演化-12
3数值模拟结果与讨论18
3.1不加入稳恒磁场时的高次谐波-18
3.2加入不同磁场的高次谐波谱-20
3.3附加稳恒磁场对谐波强度的影响--23
4总结--25
参考文献-26
致谢--27
1绪论1.1 在强激光下与物质作用的研究在强激光下，我们所研究的物质间相互作用和激光技术的进展是同步进行的，所以说，在激光技术中的重大进展总会使得我们所研究的----激光与物质进入一个全新进展[1]。在过去的几年年里随着实验仪器和技术的发展诞生了[2]----超短脉冲激光技术它的发展为阿秒科学打下了坚实的基础[3]， 现如今我们已经能够实现在可见光和近红外光波段这一范围产生脉宽为几fs的激光脉冲中观察其产生的波形图，这些脉冲虽然只包含几个光周期的电磁振荡，却已经非常接近由激光振荡周期决定的极限宽度。在现在所研究的激光技术是可以接近激光的电场强度会比库伦力场小得多，而微扰理论正好可以用来研究和解释这一现象从而也使得微扰理论得到了进一步的发展。
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