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运用数值方法研究了超短激光脉冲在多能级系统中的传输特性.当激光脉冲能量相对较弱时,适当的脉冲面积可以实现自感应透明;激光脉冲能量逐渐增强,脉冲将产生分裂.脉冲分裂的基本面积(即脉冲实现稳定传播的最小面积)与二能级系统不同,而是A0=2π/κ,与激发态的能级个数和跃迁偶极矩密切相关.由于分裂和吸收,超短激光脉冲传输了一段距离以后,将演化为一个脉冲宽度更窄、峰值强度更高且面积为A0的超短激光脉冲.
关键词:
超短激光脉冲
多能级系统
特征时间 相似文献
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采用劈裂-伪谱方法求解激光场中的含时薛定谔方程,探讨飞秒激光脉冲中氢原子波包的演化过程.研究了氢原子激发态的径向分布,角向分布、各态布居和电子云密度随时间的变化关系.在用共振激光脉冲控制氢原子波包演化的过程中径向分布、角向分布、各态布居和电子云密度随时间发生变化,但发现径向分布和角向分布在变化的过程中始终经过一些特殊点,并从理论上分析了存在这些特殊点的原因. 相似文献
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张昌莘 《原子与分子物理学报》2006,23(1):157-162
在均匀强磁场中,当氢原子的哈密顿量中B2项不能忽略时,氢原子的库仑场对称性遭到破坏,能级简并被全部解除.在应用变分法和数值法计算氢原子的能级过程中,计算十分复杂,而应用微扰法求解氢原子的能级,存在解久期方程的n2高阶行列式的困难.本文应用简并态微扰理论和球谐函数的性质,得到久期方程中非零微扰矩阵元普遍表达式.根据非零微扰矩阵元普遍表达式的性质,可以将氢原子塞曼效应久期方程的n2高阶行列式分解成1阶到n阶共n个低阶行列式的乘积,得到氢原子塞曼效应久期方程的简化公式,使得求解均匀强磁场中氢原子塞曼效应能级过程简化.而且由该公式可以得到氢原子在低能态时塞曼效应能级的解析解.根据该久期方程的简化公式计算了n=3氢原子塞曼效应一级近似能级. 相似文献
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利用"反直觉"频率啁啾激光脉冲分析了偶能级ladder系统的布局数迁移,其中在缀饰激光场作用下N-2个中间态进行耦合.作为偶能级ladder系统的代表,我们着重分析了四能级ladder系统.研究发现如果缀饰激光场足够强且发生共振,则在能级1和能级4之间发生完全布局数迁移必须要求有一个恰当的脉冲叠加面积,调谐pump激光和stokes激光,使其中一个缀饰中间态发生共振,则可以使这个四能级系统简化为三能级系统. 相似文献
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在原子物理学中,碱金属原子的光谱可以用与描述氢原子光谱的相仿的公式来表示,其光谱项可以表示为当n较大时,咸金属原子的能级很接近氢原子的能级;当n较小时,和氢原子能级差别较显著,这里n是主量子数.同时,当角量子数1较大时,咸金属能级很接近氢原子能级;当1较小时,差别较大.以上这些规律很容易从下面这张锂原子的能级图中看出. 在学习原子物理学时,咸金属原子能级和氢原子能级的差别一般都用原子实的极化和轨道的贯穿作了很好的解释.不过多数大都只是定性地说明.关于这一问题的较完满的量子力学分析方法,如 Thomas-Fermi方法,Hartree自洽… 相似文献
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在对Nd:YAG调Q激光器进行分析和设计时,研究人员通常选择忽略激光下能级寿命对脉冲波形的影响。当激光脉宽远大于激光下能级寿命时,这种近似一般不会带来太大偏差;而当脉宽达到纳秒量级时,Nd:YAG晶体约30 ns的下能级寿命对脉冲波形的影响会变得非常严重。建立了Nd:YAG下能级寿命对输出脉冲波形影响的理论分析模型,并对窄脉宽的Nd:YAG调Q激光器的输出波形进行仿真研究。研究结果表明,在窄脉宽激光输出情形下,激光下能级寿命会导致调Q脉冲在主峰后出现尾峰,尾峰能量可达主峰能量的一倍以上。同时建立了Nd:YAG声光调Q激光器实验系统,在与仿真计算近似的条件下测量调Q脉冲波形,观察到与仿真结果一致的尾峰现象,实验验证了理论模型的正确性。 相似文献
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Peiyong Ji Shi-Tong Zhu Wen-Da Shen 《International Journal of Theoretical Physics》1998,37(6):1779-1791
The energy-level shifts of the hydrogen spectrumin curved spacetime induced by intense short laserpulses are studied. With present high-power laser pulsesthe magnitude of the energy-level shifts of highly excited hydrogen atom should bedetectable. 相似文献
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Yihan Chen 《International Journal of Theoretical Physics》2003,42(12):2891-2903
The gravitational field produced by a high-power laser pulse traveling with a velocity < c is found in the framework of higher-derivative theory of gravitation. The gravitational perturbations of the energy levels of a freely falling one-electron atom in the higher-derivative gravitational field are studied. The energy-level shifts of highly excited hydrogen atom are considered, and the influence of the additional forces included in the linearized higher-derivative gravitation on the energe level shifts of the atom is investigated. 相似文献
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By applying a method which exploits the O(4) symmetry of the nonrelativistic hydrogen atom, the Lamb shift is calculated without making the dipole approximation. Similar calculations in the dipole approximation have been previously carried out by Lieber. The advantage of our calculations is that, without introducing a cutoff-frequency, analytical and numerical results for energy-level (Lamb) shifts, in which the self-energy of the free electron is completely separated, are obtained. Since the obtained results are finite, the significance of the retardation effects is clearly demonstrated. Furthermore, a comparison is also made with the results obtained by other authors. 相似文献
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The energy-level structure of spatially indirect Coulomb complexes is investigated. Two limiting cases that correspond to
the two-dimensional hydrogen atom and planar isotropic harmonic oscillator are characterized by accidental degeneracy are
considered. Numerical calculations are used to trace the evolution of the energy-level structure between these two limiting
cases. 相似文献
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Multi-line laser transitions from one metastable triplet state to another at wavelengths of 2.92, 3.01, 2.69 and 2.60 μm have
been obtained through high pulse repetition frequency longitudinal discharge in a mixed gas of strontium vapor and helium
buffer gas. The intensity ratio of these laser lines was 5:4:4:1. As far as we know, these laser lines have never been reported
except for 3.01 μm. Some mechanisms for forming a population inversion are initially discussed on the basis of analyzing features
of corresponding energy-level structure and experimental phenomena. It is reasonable to name this kind of laser as an M–M
transition laser according to the feature of the lasing process.
Received: 15 October 2002 / Published online: 9 April 2003
RID="*"
ID="*"Corresponding author. Fax: +86-0571/8795-1328, E-mail: pbl66@zju.edu.cn 相似文献
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Based on laser radar equations, a Doppler shift model of a laser pulse beam scattered by a rotating arbitrary convex target is reported in this paper. The boundary relations between an incident pulse beam and the detected area elements are analyzed by geometric methods. The Doppler shift characteristics of the rotating cone and cylinder are discussed and the difference between the laser pulse beam and the plane wave scattered from the same rotating target is compared accordingly. Numerical simulations show that the Doppler shift is tightly relevant to their dimensions, speeds, and so on. In the same incidence conditions, the pulse beam and plane wave have difference peak values and the same Doppler shift bandwidth. If the waist radius of the pulse beam is larger, the peak value is higher, and the Doppler shifts are proportional to the speed of the rotating target. By virtue of our theoretical model, we probe into the scattered characteristics of the Doppler shifts of a laser pulse beam, which would benefit target identification in national defense. 相似文献
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Temperature dependence of the energy-level shift induced by the Bose—Einstein condensation of photons 下载免费PDF全文
We investigate the energy-level shift of a hydrogen atom in a two-dimensional optical microcavity, where there exists a Bose-Einstein condensation of photons. It is found that below the critical temperature T c , the energy-level shift of the bound electron is dependent on temperature, and it is a monotonically increasing function of the absolute temperature T . Especially, at the absolute zero temperature, the energy-level shift entirely comes from the Lamb shift, and the atom can be treated approximately, that is, in vacuum. 相似文献
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通过数值求解二维含时薛定谔方程研究了氢分子离子在圆偏振XUV少周期激光电场中的单光子电离,结果观察到不同核间距的氢分子离子的光电子能谱的能移现象.分析表明,在少周期激光场宽频情况下,分子电离电子的双中心干涉改变了夫兰克-康登因子的单调递减趋势,使不同核间距氢分子离子的光电子能谱出现能量移动. 相似文献
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A. L. Semenov 《Physics of the Solid State》2011,53(11):2339-2342
The equation of the photoinduced dynamics for atoms of the crystal lattice of Bi has been obtained. The time dependence of
atomic shifts under the effect of an ultrashort laser pulse on the crystal has been calculated based on this equation. It
has been shown that the frequency of the oscillating part of the shifts depends on the energy density of the laser pulse and
time. The intensity of the Fourier spectrum of photoinduced coherent vibrations of the crystal lattice (coherent phonons)
has been calculated. The obtained theoretical results have been compared with the experimental data. 相似文献