迭加态原子高次谐波发射的选频提高

本文研究了由体系的基态和较高激发态迭加形成的原子在强激光场作用下的高次谐波发射.观察电离波包的演化过程,阐明了谐波发射效率提高的原因.在给定入射激光条件下,通过选择不同的激发态,可以实现对谐波发射的控制.     

联合双原子在组合脉冲辐照下的高次谐波发射

首先采用经典的“三步模型“理论,分析了一维普薛耳-特勒势(P-T势)模型原子在组合脉冲作用下的动力学行为,进而利用该组合脉冲辐照联合双原子模型,通过调节组合脉冲的场幅、相位以及设定原子的核间距,使原子有适当的电离和较大的复合效率,因而在截止位置远达Ip 8Up处获得了效率高达10-9的高次谐波发射.     

原子发射高次谐波偏振态的调控

利用分裂算符法数值求解二维含时薛定谔方程研究了He原子在反旋双色组合激光场(由椭圆极化的基频场与圆极化的三倍频场构成)中产生高次谐波的偏振特性.研究结果表明,改变基频场的椭偏率、强度及相位可实现对高次谐波偏振态从圆偏振到椭圆偏振以及线偏振的完全调控,为实验室产生偏振态可控的紫外-软X射线光源提供了参考.     

一维模型原子在组合脉冲辐照下的高次谐波发射

本文采用SMT（sknple man’s theory）仔细分析了一维普薛耳-特勒势（P—T势）模型原子在高、低频组合强激光脉冲辐照下电子的动力学行为。并且，在此基础上，着力讨论了电离电子在激光脉冲策动下回核并与之复合从而发射高次谐波的平台结构，采用一种特殊设计的高、低频脉冲组合方案。使谐波发射效率较之于只用单一低频激光时的谐波发射效率提高两个数量级。     

一维模型原子在组合脉冲辐照下的高次谐波发射

本文采用SMT (simple man's theory) 仔细分析了一维普薛耳-特勒势(P-T势)模型原子在高、低频组合强激光脉冲辐照下电子的动力学行为.并且, 在此基础上,着力讨论了电离电子在激光脉冲策动下回核并与之复合从而发射高次谐波的平台结构.采用一种特殊设计的高、低频脉冲组合方案,使谐波发射效率较之于只用单一低频激光时的谐波发射效率提高两个数量级.     

利用啁啾激光调制分子谐波信号

数值研究了啁啾激光驱动H_2~+辐射谐波的特点.结果表明,(1)在低强度和高强度激光驱动下,谐波光谱分别呈现红移和蓝移现象.引入正负向啁啾参数后,谐波频移和谐波辐射强度都可以得到调控.(2)谐波光谱在高强度激光驱动下呈现非奇次谐波.理论分析表明,非奇次谐波产生的原因是双H核频移不一致所导致的不对称相消干涉引起的.     

啁啾引入时刻对H_2~+谐波光谱的影响

理论研究了长脉宽激光驱动下啁啾引入时刻对H_2~+高次谐波光谱的影响.结果表明,在长脉宽激光驱动下,H_2~+在激光前半程区域具有较高的谐波辐射效率.因此,在激光前半程引入啁啾调控可获得高强度光谱连续区.此外,在啁啾调控区域引入单极激光场可以进一步获得高能谐波连续区.最后,叠加谐波连续区的谐波,可获得39 as的孤立脉冲.     

高次谐波发射中的超拉曼发射

本文研究了单电子分子离子与强激光场相互作用下的高次谐波发射谱。从光谱中观察到除了存在入射激光频率奇数倍的谐波谱线外,还存在其他频率的超拉曼谱线。在理论上阐明了超拉曼谱线不同于高次谐波谱线的物理产生机制。研究发现当体系初态为基态和较高激发态的叠加态时能够较清晰的观察到超拉曼谱线,从而说明激发态电子的布居对超拉曼谱线的产生起着关键作用。因此在实验上,制备一个叠加态使得电子从激发态电离,是观察到超拉曼谱线的重要条件。     

强短脉冲辐照叠加态原子增强阿秒脉冲强度

采用强短激光脉冲辐照叠加态原子提高孤立阿秒脉冲的强度。数值研究表明,与强短脉冲 (脉冲宽度只有几个光学周期的超短脉冲）辐照基态原子获得孤立阿秒脉冲相比,采用叠加 态原子的方案不仅同样可以获得孤立的阿秒脉冲,而且阿秒脉冲的强度得到显著增强。     

强短脉冲辐照叠加态原子增强阿秒脉冲强度

采用强短激光脉冲辐照叠加态原子提高孤立阿秒脉冲的强度.数值研究表明,与强短脉冲(脉冲宽度只有几个光学周期的超短脉冲)辐照基态原子获得孤立阿秒脉冲相比,采用叠加态原子的方案不仅同样可以获得孤立的阿秒脉冲,而且阿秒脉冲的强度得到显著增强.     

A strong single attosecond pulse generation from an atomic superposition state with chirped laser fields

We numerically investigate the chirp-depending of supercontinuum generation with preparing He+ ions in a coherent superposition of the states 1s and 2s. The results show that the initial population of the 2s state can lead to the formation of intense supercontinuum in spectrum. By precise control of chirp parameter, the spectral width and intensity of supercontinuum harmonics increase. Moreover, with a synchronous decrease of pulse durations, the bandwidth of the intense supercontinuum increases. The time–frequency characteristic of harmonics reveals that the long quantum-path is dominated in supercontinuum-region. As a result, an intense 7-as isolated pulse with a bandwidth of 570 eV can be achieved.     

Control of the supercontinuum spectrum bandwidth and emission efficiency for intense-isolated sub 40-as pulse generation by using a coherent superposition of states

We present a systematic study for generation of intense and short single as pulse in pre-excited He-ionic medium with the use of a same-frequency laser field synthesis. By preparing He+ ions in a coherent superposition of the ground and excited states, a depth of spectral modulation efficiently decreases and the efficiency of harmonic plateau increases. By means of optimizing the laser parameters, the broadband XUV supercontinuum achieve by the superposition state scheme. It shows that by increasing the harmonic order of the supercontinuum, emission efficiency increases. The detailed view shows that the short-trajectory contributes to each supercontinuous harmonic and long-trajectory fully suppresses. Finally, by superposing some properly selected harmonics from optimal spectrum, an intense and almost transform-limited isolated 38-as pulse can be generated without phase compensation. A single isolated 5-as pulse can be achieved after phase compensation. These results are explained by using classical and quantum time-frequency analyses.     

Squeezed vacuum as an eigenstate of two-photon annihilation operator

We introduce the inverse annihilation and creation operatorsa ⁻¹ anda ^+-1 by their actions on the number states. We show that the squeezed vacuum exp(1/2;ξa ⁺²]|0> and squeezed first number state exp[1/2;ξa ⁺²]|n=1> are respectively the eigenstates of the operators (a ^†−1 a) and (aa ^+-1) with the eigenvalue ξ.     

Extending the High-Order Harmonics Plateau and Isolated Attosecond Pulse Generation in an Intense Three-Color Laser Field

We propose a method to extend the high-order harmonics plateau and generate an isolated sub-10-as pulse by adding a weak control pulse (10 fs, 1600 nm) to modify a two-color laser field (5 fs, 800 nm; 10 fs, 400 nm). The numerical results show that the plateau is extended obviously in the three-color laser field regime. Additionally, the ionization rate and classical returning kinetic-energy maps are calculated to better understand the physical origin of the high-order harmonics generation (HHG). By means of the ionization probability and the time-frequency distributions, more features of the HHG are revealed. Furthermore, our simulations show that the width of the plateau and the relative conversion efficiency of the harmonic spectra are highly dependent on the relative phase. Finally, by adjusting the relative phase and superposing a properly selected range of the HHG spectrum, an isolated attosecond pulse with a duration of 7 as is obtained.     

Generation of a Super Strong Attosecond Pulse from an Atomic Superposition State Irradiated by a Shape-Optimized Short Pulse

Using a linearly polarized, phase-stabilized 3-fs driving pulse of 800 nm central wavelength shape-optimized on its＇ascending edge by its an amplitude-reduced pulse irradiating on a superposition state of the helium atom, we demonstrate theoretically the generation of a super strong isolated 176-attosecond pulse in the spectral region of 93-124 eV. The unusually high intensity of this attosecond pulse is marked by the Rabi-like oscillations emerging in the time-dependent populations of the ground state and the continuum during the occurrence of the electron recombination, which is for the first time observed in this work.     

Generation of quantum switch and nonlocal fields with an external field in a high quality dispersive cavity

We present a scheme to prepare an optical “quantum switch”, a superposition of “open” and “closed” states. The scheme is based on the interaction of an Λ-type three-level atom with a single-mode of quantized cavity field and an external classical driving field, in the regime where the atom and fields are highly detuned. We show how this interaction can be used to generate coherent states of the cavity field in contrast to the usual method used in microwave cavity QED of injecting a coherent state into a cavity. A combination of switches could be used to prepare a quantum superposition of coherent field states located simultaneously in two cavities. Compared with previous proposals, our scheme is simplified due to economizes the Ramsey zone and the time required for the state generation is short.     

利用Raman相互作用实现未知原子态的传输

利用Λ型三能级原子与单模腔场之间的相互作用,研究简并喇曼相互作用过程中产生场-原子最大纠缠态的方法,实现量子逻辑门的方法,以及如何利用这种方法来实现未知原子态的量子隐形传送.     

两种特殊四态叠加多模叠加态光场的等N次幂H压缩

根据线性叠加原理,用多模相干态|{Z_j^*}〉q,|{-Z_j^*}〉q及其复共轭|{Z_j^*}〉q和|{-Z_j^*}〉q组成了两种四态叠加多模叠加态光场|Ψ_oe⁽⁴⁾Ⅵ〉q和|Ψ(4)oeⅦ〉q,利用多模压缩态理论研究了它们的等N次幂H压缩,结果发现:态|Ψ_oe⁽⁴⁾Ⅵ〉q和|Ψ(4)oeⅦ〉q具有完全相同的等N次幂H压缩规律;当压缩幂次N与腔模总数q之积,即qN为偶数时,态|Ψ_oe⁽⁴⁾Ⅵ〉q和|Ψ(4)oeⅦ〉q恒处于等幂次N-H最小测不准态或呈现"半相干态效应";当qN为奇数时,在不同条件下,态|Ψ_oe⁽⁴⁾Ⅵ〉q和|Ψ(4)oeⅦ〉q可以呈现三种不同状态:第一正交分量呈现等N次幂H压缩;第二正交分量呈现等N次幂H压缩; 可呈现"半相干态效应".     

奇偶相干迭加态的振幅高次方压缩

本文引入了学子消灭算符四次方算符α＾４新的正交归一本征态：奇偶相干态和奇偶相干迭加态，并研究了奇偶相干迭加态的振幅高次方压缩特性。