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Effect of laser intensity on quantum trajectories in the macroscopic high-order harmonic generation 被引量:2
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作者 Yun Pan Fuming Guo +1 位作者 Yujun Yang Dajun Ding 《Chinese Physics B》 SCIE EI CAS CSCD 2019年第11期52-59,共8页
We macroscopically investigate the effect of the laser intensity and gas density on quantum trajectories in the highorder harmonic generation of Ne atoms irradiated by few-cycle, 800-nm laser pulses. The time–frequen... We macroscopically investigate the effect of the laser intensity and gas density on quantum trajectories in the highorder harmonic generation of Ne atoms irradiated by few-cycle, 800-nm laser pulses. The time–frequency profile of the harmonics shows that the long quantum trajectory is dominant at both lower and higher gas densities for a low laser intensity. At high laser intensities, the long quantum trajectory plays an important role for lower gas densities, while the short quantum trajectory is dominant at higher gas densities. An analysis of the phase mismatch for high-order harmonic generation shows that the primary emission of the quantum trajectories is determined by dynamic changes in the laser electric field during the propagation process. 展开更多
关键词 high-order harmonic GENERATION QUANTUM TRAJECTORY
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Extension of high-order harmonics and generation of an isolated attosecond pulse in the chirped laser field 被引量:4
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作者 伍杰 翟振 刘学深 《Chinese Physics B》 SCIE EI CAS CSCD 2010年第9期319-322,共4页
This paper theoretically investigates the high-order harmonic generation cutoff extension using intense few-cycle linearly chirped laser pulses. It shows that the cutoff of the harmonic can be extended remarkably by o... This paper theoretically investigates the high-order harmonic generation cutoff extension using intense few-cycle linearly chirped laser pulses. It shows that the cutoff of the harmonic can be extended remarkably by optimising the chirping parameters. The time-frequency characteristics of high-order harmonics with different chirping parameters are analysed by means of wavelet transform of the dipole acceleration. It also gives out the classical three-step model pictures of electron. By superposing a properly selected range of the harmonic spectrum, it obtains an isolated 65as pulse. 展开更多
关键词 high-order harmonic generation isolated attosecond pulse chirped laser field
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Restraint of spatial distribution in high-order harmonic generation from a model of hydrogen molecular ion 被引量:2
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作者 夏昌龙 张军 +1 位作者 苗向阳 刘学深 《Chinese Physics B》 SCIE EI CAS CSCD 2017年第7期62-66,共5页
The spatial distribution in high-order harmonic generation(HHG) is theoretically investigated by using a few-cycle laser pulse from a two-dimensional model of a hydrogen molecular ion. The spatial distribution in HH... The spatial distribution in high-order harmonic generation(HHG) is theoretically investigated by using a few-cycle laser pulse from a two-dimensional model of a hydrogen molecular ion. The spatial distribution in HHG demonstrates that the harmonic spectra are sensitive to the carrier envelope phase and the duration of the laser pulse. The HHG can be restrained by a pulse with the duration of 5 fs in the region from the 90 th to 320th order. This characteristic is illustrated by the probability density of electron wave packet distribution. The electron is mainly located near the nucleus along the positive-x direction from 3.0 o.c. to 3.2 o.c., which is an important time to generate the HHG in the plateau area. We also demonstrate the time-frequency distribution in the region of the positive-and negative-x direction to explain the physical mechanism. 展开更多
关键词 high-order harmonic generation spatial distribution
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Quantitative Measurement of the Proportions of High-Order Harmonics for the 4B7B Soft-X-Ray Source at Beijing Synchrotron Radiation Facility 被引量:2
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作者 朱托 尚万里 +9 位作者 张文海 杨家敏 熊刚 赵阳 况龙钰 赵屹东 郑雷 崔明启 唐坤马 陈燕 《Plasma Science and Technology》 SCIE EI CAS CSCD 2013年第12期1194-1196,共3页
A transmission grating coupled with an X-ray charge coupled device (CCD) is used to quantitatively measure the proportion of high-order harmonics of the soft-X-ray source of beam line 4B7B. The results show that the... A transmission grating coupled with an X-ray charge coupled device (CCD) is used to quantitatively measure the proportion of high-order harmonics of the soft-X-ray source of beam line 4B7B. The results show that the monochromatic X-ray has third-order and second-order harmonics. The proportion of second-order harmonic of 4B7B is less than 9.0% and the third- order harmonic is below 0.7% when no suppressing method is applied. When suppression methods are used, the proportion of second-order harmonic is less than 1.7% and the third-order harmonic is ignorable. 展开更多
关键词 quantitative measurement high-order harmonics suppressing method
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Selection of quantum path in high-order harmonics and isolated sub-100 attosecond generation in few-cycle spatially inhomogeneous laser fields 被引量:2
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作者 葛鑫磊 杜慧 +2 位作者 王群 郭静 刘学深 《Chinese Physics B》 SCIE EI CAS CSCD 2015年第2期116-121,共6页
We theoretically study the selection of the quantum path in high-order harmonics(HHG) and isolated attosecond pulse generation from a one-dimensional(1D) model of a H_2~+ molecule in few-cycle inhomogeneous laser... We theoretically study the selection of the quantum path in high-order harmonics(HHG) and isolated attosecond pulse generation from a one-dimensional(1D) model of a H_2~+ molecule in few-cycle inhomogeneous laser fields.We show that the inhomogeneity of the laser fields play an important role in the HHG process.The cutoff of the harmonics can be extended remarkably,and the harmonic spectrum becomes smooth and has fewer modulations.We investigate the time-frequency profile of the time-dependent dipole,which shows that the short quantum path is enhanced and the long quantum path disappears in spatially inhomogeneous fields.The semi-classical three-step model is also applied to illustrate the physical mechanism of HHG.The influence of driving field carrier-envelop phase(CEP) on HHG is also discussed.By superposing a series of properly selected harmonics,an isolated attosecond pulse(IAP) with duration 53 as can be obtained by a 15-fs,1600-nm laser pulse with the parameter ε = 0.0013(e is the parameter that determines the order of inhomogeneity of the laser field). 展开更多
关键词 high-order harmonic generation isolated attosecond pulse spatially inhomogeneous fields
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A scaling law of high-order harmonic generation 被引量:1
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作者 Wu Yan Ye Hui-Liang +1 位作者 Shao Chu-Yin Zhang Jing-Tao 《Chinese Physics B》 SCIE EI CAS CSCD 2012年第2期351-356,共6页
Using a nonperturbative quantum electrodynamics theory of high-order harmonic generation (HHG), a scaling law of HHG is established. The scaling law states that when the atomic binding energy Eb, the wavelength ), ... Using a nonperturbative quantum electrodynamics theory of high-order harmonic generation (HHG), a scaling law of HHG is established. The scaling law states that when the atomic binding energy Eb, the wavelength ), and the intensity I of the laser field change simultaneously to kEb, λ/k, and k3I, respectively. The characteristics of the HHG spectrum remain unchanged, while the harmonic yield is enhanced k3 times. That HHG obeys the same scaling law with above-threshold ionization is a solid proof of the fact that the two physical processes have similar physical mechanisms. The variation of integrated harmonic yields is also discussed. 展开更多
关键词 high-order harmonic generation scaling law harmonic yield nonperturbative quantumelectrodynamics
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High-order harmonic generation with a two-color laser pulse 被引量:1
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作者 罗老永 杜洪川 胡碧涛 《Chinese Physics B》 SCIE EI CAS CSCD 2012年第3期176-180,共5页
We theoretically investigate the electron dynamics of the high-order harmonics generation process by combining a near-infrared 800 nm driving pulse with a mid-infrared 2000 nm control field. We also investigate the em... We theoretically investigate the electron dynamics of the high-order harmonics generation process by combining a near-infrared 800 nm driving pulse with a mid-infrared 2000 nm control field. We also investigate the emission time of harmonics using time-frequency analysis to illustrate the physical mechanisms of high-order harmonic generation. We calculate the ionization rate using the Ammoso Delone-Krainov model and interpret the variations in harmonic intensity for different control field strengths and delays. We find that the width of the harmonic plateau can be extended when the control electric field is added, and a supercontinuum from 198 to 435 eV is generated, from which an isolated 61-as pulse can be directly obtained. 展开更多
关键词 high-order harmonic generation attosecond pulse
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Carrier envelope phase effect on the spatial distribution of high-order harmonic generation in asymmetric molecule 被引量:1
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作者 Jun Zhang 《Chinese Physics B》 SCIE EI CAS CSCD 2016年第5期135-139,共5页
The spatial distribution in high-order harmonic generation(HHG) from the asymmetric diatomic molecule He H^(2+) is investigated by numerically solving the non-Born–Oppenheimer time-dependent Schr?dinger equatio... The spatial distribution in high-order harmonic generation(HHG) from the asymmetric diatomic molecule He H^(2+) is investigated by numerically solving the non-Born–Oppenheimer time-dependent Schr?dinger equation(TDSE). The spatial distribution of the HHG spectra shows that there is little contribution in HHG around the geometric center of two nuclei(z = 1.17 a.u.) and the equilibrium internuclear position of the H nucleus(z = 3.11 a.u.). We demonstrate the carrier envelope phase(CEP) effect on the spatial distribution of HHG in a few-cycle laser pulse. The HHG process is investigated by the time evolution of the electronic density distribution. The time–frequency analysis of HHG from two nuclei in HeH^(2+) is presented to further explain the underlying physical mechanism. 展开更多
关键词 high-order harmonic generation spatial distribution asymmetric molecule carrier envelope phase
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Extension of high-order harmonic cutoff frequency by synthesizing the waveform of a laser field via the optimization of classical electron trajectory in the laser field 被引量:1
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作者 赵迪 李福利 《Chinese Physics B》 SCIE EI CAS CSCD 2013年第6期424-430,共7页
We theoretically investigate high-order harmonic generation by employing strong-field approximation (SFA) and present a new approach to the extension of the high-order harmonic cutoff frequency via an exploration of... We theoretically investigate high-order harmonic generation by employing strong-field approximation (SFA) and present a new approach to the extension of the high-order harmonic cutoff frequency via an exploration of the dependence of high-order harmonic generation on the waveform of laser fields. The dependence is investigated via detailed analysis of the classical trajectories of the ionized electron moving in the continuum in the velocity-position plane. The classical trajectory consists of three sections (Acceleration Away, Deceleration Away, and Acceleration Back), and their relationship with the electron recollision energy is investigated. The analysis of classical trajectories indicates that, besides the final (Acceleration Back) section, the electron recollision energy also relies on the previous two sections. We simultaneously optimize the waveform in all three sections to increase the electron recollision energy, and an extension of the cutoff frequency up to Ip + 20.26Up is presented with a theoretically synthesized waveform of the laser field. 展开更多
关键词 high-order harmonic generation classical electron trajectory cutoff frequency extension
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Atomic high-order harmonic generation from a circularly polarized laser pulse 被引量:1
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作者 郭福明 陈高 +2 位作者 陈基根 李苏宇 杨玉军 《Chinese Physics B》 SCIE EI CAS CSCD 2013年第2期193-197,共5页
We demonstrate theoretically that the high-order harmonic of an atom can be generated by a circularly polarized laser pulse.The harmonic spectrum shows a clear cutoff with an energy Ip + 2Up.In particular,the high-or... We demonstrate theoretically that the high-order harmonic of an atom can be generated by a circularly polarized laser pulse.The harmonic spectrum shows a clear cutoff with an energy Ip + 2Up.In particular,the high-order harmonic generation comes from the multiple recombination of the ionized electron with non-zero initial velocity.These results are verified by the classical model theory and the time-frequency analysis of a harmonic spectrum. 展开更多
关键词 high-order harmonic generation circularly polarized intense laser
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High-order harmonic generation in a two-color strong laser field with Bohmian trajectory theory 被引量:1
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作者 Yi-Yi Huang Xuan-Yang Lai Xiao-Jun Liu 《Chinese Physics B》 SCIE EI CAS CSCD 2018年第7期295-300,共6页
We theoretically study the high-order harmonic generation (HHG) in a two-color laser field using the Bohmian mechanics. Our results show that, for tile case of a weak second-color laser field, the simulation of the ... We theoretically study the high-order harmonic generation (HHG) in a two-color laser field using the Bohmian mechanics. Our results show that, for tile case of a weak second-color laser field, the simulation of the HHG with only one central Bohmian trajectory is in a good agreement with the ab initio time-dependent Schrodinger equation (TDSE) results. In contrast, with the increase of the amplitude of the second-color laser field, the HHG spectra from the single central Bohmian trajectory deviate from the TDSE results more and more significantly. By analyzing the Bohmian trajectories, we find that the significant deviation is due to the fact that the central Bohmian trajectory leaves the core quickly in the two-color laser field with the breaking of inversion symmetry. Interestingly, we find that another Bohmian trajectory with different initial position, which keeps oscillating around the core, could qualitatively well reproduce the TDSE results. Furthermore, we study the HHG spectrum in a two-color laser field with inversion symmetry and find that the HHG spectrum in TDSE can be still well simulated with the central Bohmian trajectory. These results indicate that, similar to the case of one color laser field, the HHG spectra in a two-color laser field can be also reproduced with a single Bohmian trajectory, although the initial position of the trajectory is dependent on the symmetry of the laser field. Our work thus demonstrates that Bohmian trajectory theory can be used as a promising tool in investigating the HHG process in a two-color laser field. 展开更多
关键词 high-order harmonic generation two-color laser field Bohmian trajectory
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High-order harmonic generation of N2molecule in two-color circularly polarized laser fields 被引量:1
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作者 杜慧 张军 +4 位作者 贲帅 钟慧英 徐彤彤 郭静 刘学深 《Chinese Physics B》 SCIE EI CAS CSCD 2016年第4期104-109,共6页
The generation of high-order harmonics and the attosecond pulse of the N2 molecule in two-color circularly polarized laser fields are investigated by the strong-field Lewenstein model. We show that the plateau of spec... The generation of high-order harmonics and the attosecond pulse of the N2 molecule in two-color circularly polarized laser fields are investigated by the strong-field Lewenstein model. We show that the plateau of spectra is dramatically extended and a continuous harmonic spectrum with the bandwidth of 113 eV is obtained. When a static field is added to the x direction, the quantum path control is realized and a supercontinuum spectrum can be obtained, which is beneficial to obtain a shorter attosecond pulse. The underlying physical mechanism is well explained by the time-frequency analysis and the semi-classical three-step model with a finite initial transverse velocity. By superposing several orders of harmonics in the combination of two-color circularly polarized laser fields and a static field, an isolated attosecond pulse with a duration of 30 as can be generated. 展开更多
关键词 high-order harmonic generation two-color circularly polarized laser fields attosecond pulse
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Controlling the contributions to high-order harmonic generation from different nuclei of N_2 with an orthogonally polarized two-color laser field 被引量:3
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作者 杜慧 潘雪飞 +4 位作者 刘海凤 张宏丹 张军 郭静 刘学深 《Chinese Physics B》 SCIE EI CAS CSCD 2016年第9期303-309,共7页
The generation of high-order harmonic and the attosecond pulse of the N2 molecule with an orthogonally polarized two-color laser field are investigated by the strong-field Lewenstein model.We show that the control of ... The generation of high-order harmonic and the attosecond pulse of the N2 molecule with an orthogonally polarized two-color laser field are investigated by the strong-field Lewenstein model.We show that the control of contributions to high-order harmonic generation(HHG) from different nuclei is realized by properly selecting the relative phase.When the relative phase is chosen to be φ= 0.4π,the contribution to HHG from one nucleus is much more than that from another.Interference between two nuclei can be suppressed greatly; a supercontinuum spectrum of HHG appears from 40 e V to125 e V.The underlying physical mechanism is well explained by the time–frequency analysis and the semi-classical threestep model with a finite initial transverse velocity.By superposing several orders of harmonics,an isolated attosecond pulse with a duration of 80 as can be generated. 展开更多
关键词 high-order harmonic generation orthogonally polarized two-color laser field attosecond pulse
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High-order harmonic generation spectrum of an excited one-dimensional Coulomb atom in an intense laser field
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作者 周兆妍 袁建民 《Chinese Physics B》 SCIE EI CAS CSCD 2007年第3期675-679,共5页
Response of the wave packet of a one-dimensional Coulomb atom to an intense laser field is calculated using the symmetrized split operator fast Fourier method. The high-order harmonic generation (HHG) of the initial... Response of the wave packet of a one-dimensional Coulomb atom to an intense laser field is calculated using the symmetrized split operator fast Fourier method. The high-order harmonic generation (HHG) of the initial state separately being the ground and excited states is presented. When the hardness parameter a in the soft Coulomb potential V(x) =-1√x^2+α is chosen to be small enough, the so-called hard Coulomb potential V(x)=1/|x| can be obtained. It is well known that the hard one-dimensional Coulomb atom has an unstable ground state with an energy eigenvalue of - 0.5 and it has no states corresponding to physical states in the true atoms, and has the first and second excited states being degenerate. The parity effects on the HHG can be seen from the first and second excited states of the hard one-dimensional Coulomb atom. The HHG spectra of the excited states from both the soft and hard Coulomb atom models are shown to have more complex structures and to be much stronger than the corresponding HHG spectrum of the ground state of the soft Coulomb model with a = 2 in the same laser field. Laser-induced non-resonant one-photon emission is also observed. 展开更多
关键词 high order harmonic generation intense laser field one-dimensional Coulomb atom
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Optimization of multi-color laser waveform for high-order harmonic generation 被引量:1
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作者 金成 林启东 《Chinese Physics B》 SCIE EI CAS CSCD 2016年第9期157-168,共12页
With the development of laser technologies,multi-color light-field synthesis with complete amplitude and phase control would make it possible to generate arbitrary optical waveforms.A practical optimization algorithm ... With the development of laser technologies,multi-color light-field synthesis with complete amplitude and phase control would make it possible to generate arbitrary optical waveforms.A practical optimization algorithm is needed to generate such a waveform in order to control strong-field processes.We review some recent theoretical works of the optimization of amplitudes and phases of multi-color lasers to modify the single-atom high-order harmonic generation based on genetic algorithm.By choosing different fitness criteria,we demonstrate that:(i) harmonic yields can be enhanced by 10 to 100 times,(ii) harmonic cutoff energy can be substantially extended,(iii) specific harmonic orders can be selectively enhanced,and(iv) single attosecond pulses can be efficiently generated.The possibility of optimizing macroscopic conditions for the improved phase matching and low divergence of high harmonics is also discussed.The waveform control and optimization are expected to be new drivers for the next wave of breakthrough in the strong-field physics in the coming years. 展开更多
关键词 high-order harmonic generation waveform optimization genetic algorithm single-attosecond pulse
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Spectral redshift of high-order harmonics by adding a weak pulse in the falling part of the trapezoidal laser pulse 被引量:1
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作者 潘雪飞 张军 +2 位作者 贲帅 徐彤彤 刘学深 《Chinese Physics B》 SCIE EI CAS CSCD 2018年第2期374-379,共6页
We investigate the spectral redshift of high-order harmonics of the H_2~+(D_2~+) molecule by numerically solving the non-Born–Oppenheimer time-dependent Schr ¨odinger equation(TDSE). The results show that ... We investigate the spectral redshift of high-order harmonics of the H_2~+(D_2~+) molecule by numerically solving the non-Born–Oppenheimer time-dependent Schr ¨odinger equation(TDSE). The results show that the spectral redshift of highorder harmonics can be observed by adding a weak pulse in the falling part of the trapezoidal laser pulses. Comparing with the H_2~+ molecule, the shift of high-order harmonic generation(HHG) spectrum for the D_2~+ molecule is more obvious.We employ the spatial distribution in HHG and time-frequency analysis to illustrate the physical mechanism of the spectral redshift of high-order harmonics. 展开更多
关键词 high-order harmonic generation spectral redshift trapezoidal laser pulse spatial distribution
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High-order harmonic generations in tilted Weyl semimetals
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作者 Zi-Yuan Li Qi Li Zhou Li 《Chinese Physics B》 SCIE EI CAS CSCD 2022年第12期242-251,共10页
We investigate high-order harmonic generations(HHGs)under comparison of Weyl cones in two types.Due to the hyperboloidal electron pocket structure,strong noncentrosymmetrical generations in high orders are observed ar... We investigate high-order harmonic generations(HHGs)under comparison of Weyl cones in two types.Due to the hyperboloidal electron pocket structure,strong noncentrosymmetrical generations in high orders are observed around a single type-ⅡWeyl point,especially at zero frequency.Such a remarkable DC signal is proved to have attributions from the intraband transition after spectral decomposition.Under weak pulse electric field,the linear optical response of a nontilted Weyl cone is consistent with the Kubo theory.With extensive numerical simulations,we conclude that the non-zero chemical potential can enhance the even-order generations,from the slightly tilted system to the over-tilted systems.In consideration of dynamical symmetries,type-Ⅰand type-ⅡWeyl cones also show different selective responses under the circularly polarized light.Finally,using a more realistic model containing two pairs of Weyl points,we demonstrate that paired Weyl points with opposite chirality can suppress the overall even-order generations. 展开更多
关键词 high order harmonic generation nonlinear optics Weyl semimetals
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High-order harmonic generation and multi-photon ionization of Na2 in laser fields
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作者 张艳萍 张丰收 +1 位作者 蒙克来 肖国青 《Chinese Physics B》 SCIE EI CAS CSCD 2007年第1期83-87,共5页
In this paper high-order harmonic generation (HHG) spectra and the ionization probabilities of various charge states of small cluster Na2 in the multiphoton regimes are calculated by using time-dependent local densi... In this paper high-order harmonic generation (HHG) spectra and the ionization probabilities of various charge states of small cluster Na2 in the multiphoton regimes are calculated by using time-dependent local density approximation (TDLDA) for one-colour (1064 nm) and two-colour (1064 nm and 532 nm) ultrashort (25 fs) laser pulses. HHG spectra of Na2 have not the large extent of plateaus due to pronounced collective effects of electron dynamics. In addition, the two-colour laser field can result in the breaking of the symmetry and generation of the even order harmonic such as the second order harmonic. The results of ionization probabilities show that a two-colour laser field can increase the ionization probability of higher charge state. 展开更多
关键词 high-order harmonic spectra ionization probabilities TDLDA
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Effect of electron correlation on high-order harmonic generation in helium model atom
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作者 胡师林 史庭云 《Chinese Physics B》 SCIE EI CAS CSCD 2013年第1期171-174,共4页
High-order harmonic generation (HHG) of a helium model atom in an intense laser field has been numerically investigated. The influence of electron correlation on HHG is analysed by changing the strength between the ... High-order harmonic generation (HHG) of a helium model atom in an intense laser field has been numerically investigated. The influence of electron correlation on HHG is analysed by changing the strength between the electrons. The numerical results show that as the electron interaction strength becomes small, the first ionization energy increases rapidly, which results in the decrease in ionization. So the conversion efficiency of the high harmonic lying in the plateau decreases greatly, while the cutoff harmonic order in the harmonic spectrum increases. 展开更多
关键词 electron correlation high-order harmonic generation B-SPLINE
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Generation-channel interference of high-order harmonics of an anharmonic oscillator driven by bi-chrime laser fields and its mechanism
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作者 王黎明 蔡俊 乔豪学 《Chinese Physics B》 SCIE EI CAS CSCD 2011年第7期142-150,共9页
A method to describe the generation channels of high-order harmonics is proposed. According to this method, the mechanism of generation-channel interference of high-order harmonics is revealed clearly. We take the anh... A method to describe the generation channels of high-order harmonics is proposed. According to this method, the mechanism of generation-channel interference of high-order harmonics is revealed clearly. We take the anharmonic oscillator driven by bi-chrome fields as an example to illustrate that this method can be used to understand the effect of generation-channel interference. 展开更多
关键词 generation-channel interference anharmonic oscillator high-order harmonics
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