共查询到20条相似文献,搜索用时 15 毫秒
1.
Chang-Long Xia 《光谱学快报》2013,46(8):605-609
We numerically solve the two-dimensional Schrödinger equation and investigate isolated attosecond pulse generation by combining a left and a right elliptically polarized pulse together. It is found that the plateau of the harmonic spectra can be extended and the quantum paths can be controlled by adjusting ellipticity. A broadband width of about 220 eV is generated for the case that ellipticity equals 0.3, and time-frequency time–frequency analysis shows that only one long quantum path contributes to high-order harmonic generation. By superposing a bandwidth of 60 eV near the cutoff of the harmonic plateau, an attosecond pulse with the duration of about 62 as could be generated. 相似文献
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High-Order-Harmonic Generation from a Relativistic Circularly Polarized Laser Interacting with Over-Dense Plasma Grating 下载免费PDF全文
《中国物理快报》2017,(9)
The simple surface current model is extended to study the generation of high-order harmonics for a relativistic circularly polarized laser pulse interacting with a plasma grating surface. Both exact relativistic electron dynamics and optical interference of surface periodic structure are considered. It is found that high order harmonics in the specular direction are obviously suppressed whereas the harmonics of the grating periodicity are strongly enhanced and folded into small solid angles with respect to the surface direction. The conversion efficiency of certain harmonics is five orders of magnitude higher than that of the planar target cases. It provides an effective approach to generate a coherent radiation within the so-called ‘water window' while maintaining high conversion efficiency and narrow angle spread. 相似文献
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We calculate nonperturbatively the irfluence of a strong circularly polarized laser beam on the hydrogen atom energy levels by making use of the time-independent formalism proposed by one of us. The photoionization cross section of the hydrogen atom irradiated by this laser beam and the angular distribution of photoelectrons are also calculated. From the numerical results we clearly see the intensity dependence of the whole photoionization process,including the intensity dependence of the photoelectron energies. 相似文献
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ZHANG Deng ZHANG Qi-Ren 《理论物理通讯》2001,(12)
We calculate nonperturbatively the irfluence of a strong circularly polarized laser beam on the hydrogen atom energy levels by making use of the time-independent formalism proposed by one of us. The photoionization cross section of the hydrogen atom irradiated by this laser beam and the angular distribution of photoelectrons are also calculated. From the numerical results we clearly see the intensity dependence of the whole photoionization process,including the intensity dependence of the photoelectron energies. 相似文献
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Ionization rate for circular polarization laser field is reformulated in length gauge. The Volkov state or the Coulomb-correctsd Volkov one is served at the final wavefunction and would lead to that the ionization rate in length gauge is closer to the experimental data than the corresponding result in velocity gauge. It is also found that the ionization rate as a function of laser intensity has nevertheless the stabilization effect, although in the sense more weakly in length gauge than in velocity gauge, when the field is to be comparable or exceeds to the atomic binding field. 相似文献
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ZHANG Qiren 《理论物理通讯》1997,28(3):355-358
The intensity dependence of the energy and the angular distribution for photoelectrons ejected by a circularly polarized laser beam is derived. The energy shift is similar to that of a combined Zeeman-Stark effect in magnetic and electric fields perpendicular to each other. 相似文献
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CHEN BaoZhen 《理论物理通讯》2000,33(4):521-524
A new analytic model for ATIspectra of He in circularly polarized laser is proposed.The model gives a way to describe the effects of the final state Coulomb interaction and the joint interaction of the atomic potential and laser field. The experimental spectra by Mohideen et al. can be quite well described. The peak intensity contradiction, which appeared in previous literatures, can be considerably eliminated. 相似文献
9.
Hua Yuan Lixin He Stephen Maina Njoroge Dian Wang Renzhi Shao Pengfei Lan Peixiang Lu 《Annalen der Physik》2020,532(5):1900570
A method to produce circularly polarized attosecond pulses with tunable helicity from CO molecule by using an unidirectionally rotating laser field is proposed. It is found that broadband harmonic supercontinuum with circular polarization can be generated from the oriented CO molecule. This enables the production sub-100 attosecond isolated pulse with the ellipticity as high as 0.9 at the macroscopic level. Moreover, the helicity of the generated high-order harmonics and the attosecond pulse can be tuned by adjusting the orientation of the CO molecule. This method will be beneficial for the studies on chiral-specific dynamics and magnetic circular dichroism on an attosecond time scale. 相似文献
10.
An efficient method for attosecond extreme ultraviolet source generation under the two-color multi-cycle weak pulse has been theoretically presented by using the concept of the plasmonic field enhancement in the vicinity of metallic nanostructures. The results show that by properly choosing the inhomogeneity of the two-color multi-cycle(20 fs) weak pulse(1013W/cm2), not only the harmonic cutoff has been extended, resulting in a broadband XUV continuum, but also the single short quantum path has been selected to contribute to the harmonic. As a result, two isolated XUV pulses with durations of 68 as and 66 as can be obtained. 相似文献
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We theoretically investigate high-order harmonic and isolated attosecond pulse generation in a two-color chirped laser field,which is synthesized by a 9 fs/800 nm fundamental chirped pulse and a 9 fs/1600 nm controlling chirped pulse.Our numerical results show that,by using this method,not only is the harmonic cutoff significantly extended to the 948th order harmonic,but also the bandwidth of the supercontinuum spectrum is effectively broadened to about 1342 eV.In addition,due to the introduction of the chirp,the long quantum path is suppressed and only the short one is selected,and then an isolated 28 as pulse with a bandwidth of 155 eV is obtained directly. 相似文献
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Decoherence Effects of Terahertz Generation in Solids under Two-Color Femtosecond Laser Fields 下载免费PDF全文
We theoretically investigate terahertz emission from solid materials pumped by intense two-color femtosecond laser field in the presence of decoherence effects.Quantum-mechanical simulations are based on the length gauge semiconductor Bloch equations describing the optical excitation and decoherence with phenomenological dephasing and depopulation times.Contributions of interband and intraband mechanisms are identified in time domain,and the latter has dominated THz generation in solid-state sys... 相似文献
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An efficient method to enhance the harmonic efficiency and generate an isolated attosecond pulse is proposed by preparing the initial state as a coherent superposition of the ground state and a Rydberg state in a two-color laser field. By numerically solving the time-dependent Schrödinger equation, we found that for the superposition state with the optimal Rydberg state, not only is the harmonic efficiency enhanced significantly, but also the width of the continuous spectrum is extended. The ionization probability and the time-frequency distribution of the harmonic spectrum are also calculated to understand the physical origin of the enhancement of the harmonic spectrum. In addition, by adjusting the parameter of the laser pulse, a supercontinuum with both higher conversion efficiency and slighter modulation can be observed. As a result, an isolated 7-as pulse with a bandwidth of 495 eV can be obtained after phase compensation. 相似文献
15.
V. A. Tolkachev 《Journal of Applied Spectroscopy》2001,68(2):308-313
It is shown that the magnetic fieldinduced optical activity in the luminescence of complex molecules in vapors in the presence of rotational anisotropy in the ensemble of luminescent molecules provides information also on the intramolecular orientation of the initiating dipole moments of transitions, including borrowed ones. The relationships between the rotational force of the optical activity and this orientation in the case of anisotropy induced by a linearly polarized exciting light are obtained. 相似文献
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在强激光场中三维二能级氢原子模型的基础上, 对其含时Schr\"{o}dinger方程进行了非微扰的数值求解, 得到了激光场的高次谐波谱. 相似文献
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Effect of Time-Dependent Ionization on Propagation of a Few-Cycle Circularly Polarized Laser Pulse in Two-Level Medium 下载免费PDF全文
Influence of multiphoton ionization on the propagation and spectrum of few-cycle circularly (elliptically) polarized laser pulses in an open two-level medium (two-level plus continuum model) is investigated based on the conventional two-level model proposed by Slavcheva and Hess (Phys. Rev. A 72 (2005) 053804), and the propagation dynamics of an arbitrary elliptically polarized laser pulse is reduced into that of right and left circularly polarized laser pulses. When the laser intensity is high enough to cause ionization, there are significant impacts of ionization on the pulse reshaping and on the higher order spectral components, and the impacts for the open two-level model are different from those for the dosed two-level model. 相似文献
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We perform an experimental study on high-order harmonic generation (HHG) of aligned acetylene molecules induced by a 35-fs 800-nm strong laser field, by using a home-built HHG spectrometer. It is observed that the molecular HHG probability declines with increasing the laser ellipticity, which is in consistence with the deduction from the well-known tunneling-plus-rescattering scenario. By introducing a weak femtosecond laser pulse to nonadiabatically align the molecules, we investigated the molecular orbital effect on the HHG in both linearly and elliptically polarized driving laser fields. The results show that the harmonic intensity is maximum for the molecular axis aligned perpendicularly to the laser electric field. It indicates that both the highest occupied molecular orbitals (HOMO) and HOMO-1 contribute to the strong-field HHG of acetylene molecules. Our study should pave the way for understanding the interaction of molecules with ultrafast strong laser fields. 相似文献