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1.
樊锡君  田淑芬  刘杰  李健 《光子学报》2000,29(6):492-496
本文给出了有初始相干性注入的V型无粒子数反转激光系统的非线性注解,分析了 系统参量变化对无粒子数反转激光增益和与探测场相互作用的两能级之间的粒子数差的影 响,我们发现伴随着驱动场Rabi频率的增加,粒子数差的变化表现出一个振荡行为,我们对这一新现象给出了解释。  相似文献   

2.
非相干泵浦对原子系统位相相关吸收性质的影响   总被引:1,自引:1,他引:0  
研究发现在具有真空诱导相干性的开放和封闭ladder 型原子系统中,探测场和驱动场之间相对位相对吸收性质有重要的调制作用,同时非相干泵浦对位相相关的吸收性质有显著的影响.在这两种系统中,通过调节非相干泵浦,可以实现从吸收到增益和从粒子数反转激光到无粒子数反转激光的转化,并可获得最大的无反转激光增益.但是,当非相干泵浦不存在时,对相对位相的任意值,在封闭系统中只出现吸收而不能得到无反转激光增益;然而在开放系统中,对于适当的相对位相值甚至可以产生比有非相干泵浦时更大的无反转激光增益.  相似文献   

3.
常增光  刘建成  闫珂柱 《物理学报》2008,57(8):4927-4932
在相应参量取值相同的情况下,利用数值模拟的方法对比研究了封闭的V型和Λ型原子系统稳态增益随相干光场失谐量的变化规律.研究发现,这两种系统的稳态探测激光增益随探测激光场失谐量的变化曲线具有相似的形状,但数值上存在差异.这一现象与两种系统的原子相干性与粒子数分布的特点直接相关.另外,还发现驱动激光失谐及由于自发辐射诱导相干导致的原子相干性的增强能显著影响探测激光增益. 关键词: 无粒子数反转激光 失谐 原子相干性 粒子数分布  相似文献   

4.
利用由预估计校正-时域有限差分(PC-FDTD)法求解Maxwell-Bloeh方程得到的数值解,研究少周期激光脉冲在稠密Ⅴ型三能级原子介质中传播时各能级粒子数布居的演化特性.结果表明,两跃迁偶极矩的比值(γ)对稠密介质中粒子数布居反转出现的时间和振荡的次数具有显著的影响,γ=1时,考虑洛仑兹局域场修正(LFC)时,粒子数反转出现的较晚,近偶极.偶极(NDD)相互作用延缓了粒子数的反转;γ1时,考虑LFC时,粒子数反转出现的较早,NDD相互作用加快了粒子数的反转;电偶极矩不同时,粒子数布居振荡的次数比相同时多.粒子数布居在稠密介质中的演化特性与稀疏介质中显著不同,在入界处,稀疏介质中粒子数布居可以实现长时间的反转;随着介质密度的增大,粒子数布居产生准周期性的振荡,但考虑LFC时,振荡的次数比不考虑LFC时少.  相似文献   

5.
朱孟正  赵春然  尹新国  李光源 《光子学报》2007,36(12):2360-2364
在封闭的简单四能级原子系统模型的基础上提出了开放的四能级原子系统模型.通过在电偶极和旋转波近似下,解此系统的半经典密度矩阵运动方程得其稳态线性解析解.对该稳态解的数值模拟显示:随着驱动场的Rabi频率的连续增加系统会发生由输出的无粒子数反转激光到输出粒子数反转激光的转变;随着系统退出速率或者注入速率比的连续增大,系统会发生由输出的粒子数反转激光到输出无粒子数反转激光的转变;该系统能获得无吸收高色散;在稳态,探测激光上下能级粒子数差随探测场失谐的变化曲线呈弱矩形波.  相似文献   

6.
提出开放的四能级双驱动场无反转激光系统的理论模型,由电偶极和旋转波近似得到其密度矩阵方程,讨论无反转激光产生的物理机制,利用数值计算结果分析探测场和驱动场失谐对系统无反转激光增益和粒子数差的影响.  相似文献   

7.
高强  宋同强 《物理学报》2012,61(14):144205-144205
研究了在引入非相干抽运的情况下,循环跃迁的Δ型共振三能级系统中产生的无反转激光.利用主方程的方法, 导出了缀饰态中强相干场极限下布居数项和相干项的稳态近似解析解以及产生无反转激光所需要满足的条件;并利用数值模拟的方法讨论了布居数分布、 系统增益对探测场和相干场拉比频率的依赖性以及随时间的演化规律. 结果表明:无论各个参量取何值,共振Δ型三能级系统总是处于无粒子数反转的状态; 只要探测场或相干场之中有一个为强场,便可产生无反转激光; 当其中任意一个场远强于另一个场时,系统的无反转增益将不再依赖于任何一个场的拉比频率.  相似文献   

8.
本文给出了开放的非共振ladder型三能级无粒子数反转激光系统的非线性精确解,利用数值计算结果讨论了系统各参量的变化对激光场的增益和色散的影响.作者得到以下结论:当探测激光场和驱动场都共振时,无论其他参量如何变化,色散为零.当仅有探测场失谐(驱动场失谐)时,增益和色散随探测场失谐(驱动场失谐)的变化曲线分别具有偶对称性和中心对称性,当探测场和驱动场皆失谐时,这种对称性消失;适当调节探测激光场或(和)驱动场的失谐可获得最大或较大的无粒子数反转激光增益和无吸收高色散.增益和色散(粒子数差绝对值)随原子注入速率之比的增加单调增加(单调减小),且原子退出速率越大增加(减小)得越快.在探测场和驱动场适当失谐的情况下,保持系统其他参量不变,非相干泵浦速率只有在一定范围内取值时,才能获得无粒子数反转激光增益,并存在一个增益极大值.改变探测场或驱动场Rabi频率对无粒子数反转激光增益的影响与非相干泵浦速率改变时的情况类似.  相似文献   

9.
陈立  毛邦宁  王煜博  王丽敏  潘佰良 《物理学报》2007,56(12):6976-6981
建立了一个反映高重复率脉冲放电激励的Sr离子自终止激光和复合激光交替振荡的动力学模型,得到了与实测光电脉冲波形相一致的模拟结果.给出了He-Sr放电等离子中长寿命粒子、激光上下能级粒子数密度和电子温度随时间的演化过程.分析了两种激光交替振荡的发射过程、脉冲宽度特性和粒子数反转机理,认为在放电早期和余辉期电子温度的急剧升高和降低是Sr离子自终止和复合激光实现交替振荡的关键所在. 关键词: 自终止激光 复合激光 交替振荡 动力学模型  相似文献   

10.
无粒子数反转激光研究的进展   总被引:1,自引:0,他引:1  
高锦岳 《物理》1994,23(3):132-141
概括地介绍了无粒子数反转光放大与无粒子数反转激光的基本概念和原理,讨论了这种类型激光对激光科学发展的重要意义,叙述了自1962年以来科学家们所提出的几种实现无粒子数反转光放大及无粒子数反转激光的主要的理论模型和有关的实验进展,最后介绍了钠原子蒸汽中首次观察到无粒子数反转光放大的实验装置和实验结果。  相似文献   

11.
We study the effects of the relative phase, Φ, between the probe and driving fields on the transient evolution of the atomic response from different respects in an open lambda-type system with spontaneously generated coherence. We find that: variation of value of Φ will obviously change the transient evolution process, transient and stationary values of gain, absorption and dispersion but has no any effect on the transient evolution of populations. For the same value of Φ, the stationary gain without inversion (GWI) when the incoherent pumping exists is much larger than that when the incoherent pumping is absent, the time needed to reach at the stationary state when the incoherent pumping exists is much shorter than that when the incoherent pumping is absent. The initial condition varying has remarkable effects on the phase-dependent transient evolution process, transient value of GWI but doesn’t vary size of stationary value of GWI. Varying the ratio C of the atomic injection rates and exit rate γ0 has evident effects on the phase-dependent transient evolution process, transient and stationary values of GWI. Our study result shows that the transient evolution of the atomic response in the open system presents some considerable difference from that in the corresponding closed system, specially in the open system we can get much larger GWI than that in the corresponding closed system. In addition, we give a brief discussion about effects of the relative phase on the transient evolution of the atomic response in the open system without SGC, and obtain some results much different from those obtained in the open system with SGC.  相似文献   

12.
We present a general and fascinating problem of quantum entanglement (QE) that is calculated with the help of quantum Fisher information (QFI) and von Neumann entropy (VNE) for moving two-level atomic systems. We calculate numerically the temporal evolution of the state vector of the entire system under the influence of intrinsic decoherence for a moving two-level atom. We demonstrate that the phase shifts of an estimator parameter, intrinsic decoherence, and the atomic motion play an important and prominent role during the time evolution of the atomic system. We observe that there is a monotonic relation between the atomic quantum Fisher information (QFI) and quantum entanglement (QE) in the absence of atomic motion. We also show that at the revival time the local maximum values of QFI decreases gradually. A periodic behavior of QFI is observed in the presence of atomic motion, which becomes more important and remarkable for two-level atomic systems. Moreover, the atomic quantum Fisher information and entanglement demonstrate an opposite response during the time evolution in the presence of atomic motion. We show that the evolution of entanglement is more susceptible to the intrinsic decoherence; a considerable change occurs in the degree of entanglement when the intrinsic decoherence parameter increases. Intrinsic decoherence in the atom–field interaction represses the nonclassical effects of the atomic systems. Both the entanglement and the quantum Fisher information saturate to their lower levels for longer time scales in the presence of intrinsic decoherence. For larger values of intrinsic decoherence, the sudden death of entanglement is observed.  相似文献   

13.
梁颖  王军  樊锡君 《计算物理》2012,(5):775-780
数值计算具有自发辐射诱导相干性的开放V型三能级原子系统密度矩阵运动方程,分析无反转激光(LWI)增益的瞬态演化.结果表明:无论是否存在非相干抽运,探测场和驱动场间的相对位相(Ф)对增益的瞬态演化都有显著的影响;通过选择的取值可以获得更大的瞬态和稳定增益;不存在非相干抽运时,系统达到瞬态增益最大值及获得增益稳定值所需要的时间更长,演化过程中振荡幅度更大,获得的增益更大;原子退出速率r0(原子注入速率比S)的变化将使增益瞬态演化的具体过程发生改变,在r0(S)的一定取值范围内,瞬态和稳定增益随S(r0)的增大而增大.  相似文献   

14.
15.
Using the numerical calculation results, the transient evolution processes and steady outputs of the continuous wave lasing without inversion (LWI) originating from Pitchfork bifurcation instability and self-pulsing LWI originating from Hopf bifurcation instability in a resonant open Λ-type three level atomic system are studied. We found that the two kinds of LWI have some obvious differences not only from the steady outputs but also from the transient evolution processes. The effects of the unsaturated gain coefficient, cavity loss coefficient, ratio of the atomic injection rates and atomic exit rate on the transient evolution processes and steady outputs are discussed.  相似文献   

16.
In an open ladder-type resonant atomic system,variation in relative phase between probe and driving fields does not affect the transient evolution of populations,but it has remarkable effects on gain and dispersion of the probe field.No matter whether an incoherent pump is present or absent,transient and stationary gains without inversion(GWI) always can be obtained by choosing an appropriate value of the relative phase.When the incoherent pump is absent the values of transient and stationary GWIs are much larger and the time interval required to reach the stationary value is longer than those when the incoherent pump is present.Varying the exit rate and the ratio between injection rates can obviously change the phase-dependent GWI.In addition,in the transient evolution process,the phenomenon of high dispersion(refractive index) without absorption occurs at some values of relative phase.In the corresponding closed system,the stationary GWI can be obtained by choosing an appropriate value of relative phase only when incoherent pump exists,moreover the gain is smaller than that in the open system.  相似文献   

17.
We consider the problem of an atomic three-level system (in a ladder configuration) interacting with a radiation field. Assuming a coherent state as the initial state, we solve exactly the time evolution of the system. We discuss the appearance of atomic squeezing and calculate the atomic spin squeezing and the atomic entropy squeezing. We show that both parameters predict similar angular and time dependences.  相似文献   

18.

Dynamical behaviour of Quantum Entanglement (QE) and atomic Quantum Fisher Information (AQFI) for a moving N-level atomic system is studied in a thermal environment. Time evolution of state vector of the entire system interacting with thermal field is calculated numerically in the presence of intrinsic decoherence. It is observed that intrinsic decoherence and thermal environment play dominant role during the time evolution of the quantum system. AQFI and entanglement show an opposite behaviour during its time evolution in the presence of thermal environment. AQFI is observed to be more prone to intrinsic decoherence as compared to the entanglement in a thermal environment. AQFI is found to be more prone to intrinsic decoherence as compared to the QE in a thermal environment. QE is found decaying when the parameter of intrinsic decoherence is increased in the absence of atomic motion. The damping behaviour of QE is observed for longer time-scales. The periodic response of entanglement due to atomic motion becomes moderate under the influence of these environments. The intrinsic decoherence and thermal environment are found to suppress the nonclassical effects of the quantum system. QE and AQFI saturate to a lower level for larger time-scales under the influence of these environments. Furthermore, the dynamics of AQFI and von Neumann entropy (VNE) changes remarkably by changing the mean number of photons.

  相似文献   

19.
通过调节动静态理想光子禁带模型库的结构参数,研究了初态处于激发态的两能级原子系统的演化.在静态无调制下研究理想光子禁带模型库环境的半宽度、中心谐振频率及比重对原子布居数演化的影响.在理想光子禁带库环境的中心共振频率受动态调制下,其调制形式分别取为:矩形单次脉冲、矩形周期性脉冲和缓变连续周期.在此基础上讨论动态调制形式的不同对原子布居数演化的影响.无论怎样的动态调制形式,衰减抑制在原子系统的演化过程还是有较明显的体现.这样就使得利用环境变化对原子布居数和原子系统相干性演化调制的想法得以实现.  相似文献   

20.
We start from the microscopic Hamiltonian formulated by means of creation and annihilation operators for the field modes, and creation and annihilation operators for the electrons. The virtual transitions via the intermediate atomic level are eliminated by second order perturbation theory so that an effective Hamiltonian results which describes two-photon creation or annihilation. In the next step Heisenberg equations of motion are derived for the field amplitudes, the atomic dipole moments, and the inversion. The effect of heatbaths is taken into account by means of damping terms and fluctuating forces. In the present paper these equations are averaged over the fluctuating forces and the resulting semiclassical equations are solved for the stationary state. We treat the degenerate and nondegenerate case including detuning and atomic levels with homogeneous and inhomogeneous broadening. The field modes may be either running or standing waves. A detailed discussion of the laser condition is given.  相似文献   

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