Local Control of Two-Photon Absorption in a Six-Level Atomic System by Using a Coherent Perturbation Field

If a coherent perturbation field is used to couple the excited level of the coupling transition in the five-level K-type atom with another higher excited level, the two-photon electromagnetically induced transparency can be locally modulated by altering the parameters of the additional perturbation field. With different detunings of the coherent perturbation field, the absorption peak or transparency window with sharp and high-contrast speetrM feature can be generated in the two-photon absorption spectrum. The physical interpretation of these phenomena is given in terms of the dressed states.     

电磁感应双光子光透明及共振吸收增强

研究了相干场控制下的电磁感应双光子光透明。讨论了外加相干场对双光子吸收特性的影响 ,分析了电磁感应双光子光透明及共振吸收增强的物理机制。应用密度矩阵方法推导出相干场作用下双光子吸收上能级粒子数的二阶近似表达式 ,同时利用微扰法在原子缀饰态表象中推导出双光子跃迁速率的解析表达式。并讨论了系统中多普勒效应的影响。     

Absorption properties of a driven Doppler—broadened ladder system with hyperfine structure

We have studied the absorption spectrum of a Doppler-broadened ladder system,where the highest level is coupled into two middle hyperfine sublevels by a strong coherent field.We find that,when the system is considered as homogeneous,either two or three spectral components are observed,depending on the detuning of the coherent field.but when the velocity distribution of atoms is considered,we can always observe one electromagnetically induced transparency (EIT) window with high dispersion.So the atomic hyperfine structure cannot be an impediment for obtaining EIT.     

Manipulation of multiple electromagnetically induced two-photon transparency in a six-level atomic system

In the five-level K-type atomic system, by using another control field to couple the excited level of the coupling transition to the sixth higher excited level, a six-level atomic system is constructed. In this system, the multiple electromagnetically induced two-photon transparency has been investigated. What is more, if choosing the parameters of the control fields properly the triple transparency window will reduce to a double one which means that the multiple electromagnetically induced two-photon transparency can be manipulated in this system. The physical interpretation of these phenomena is given in terms of the dressed states and the dark states.     

单光子和双光子电磁诱导透明谱的相干调制

采用一束相干外场作用在倒Y模型原子的基态与另外状态构成的跃迁上,实现对单光子和双光子电磁诱导透明谱的调制。经研究发现相干外场对单光子和双光子的吸收性质有类似的影响效果。由于相干外场的作用,吸收谱的共振点附近出现吸收峰将原单重透明谱分裂为双重透明谱。诱导的吸收峰的高度和透明谱的频谱宽度与相干外场的强度有密切关系。并用缀饰态理论解释了这些物理现象。这些研究对多通道光通信以及对原子光学性质的调控方面有积极意义。     

Electromagnetically Induced Transparency and Absorption of A Monochromatic Light Controlled by a Radio Frequency Field

Electromagnetically induced transparency and absorption of a monochromatic light controlled by a radio frequency field in the cold multi-Zeeman-sublevel atoms are theoretically investigated. These Zeeman sublevels are coupled by a radio frequency(RF) field. Both electromagnetically induced transparency and electromagnetically induced absorption can be obtained by tuning the frequency of RF field for both the linear polarization and elliptical polarization monochromatic lights. When the transfer of coherence via spontaneous emission from the excited state to the ground state is considered, electromagnetically induced absorption can be changed into electromagnetically induced transparency with the change of intensity of radio field. The transparency windows controlled by the RF field can have potential applications in the magnetic-field measurement and quantum information processing.     

激光线宽对原子相干效应的影响

该文在λ型三能级原子系统中分别讨论了耦合场和探针场线宽对电磁诱导透明(EIT)的影响,通过实验观测探针光和耦合光线宽变化时EIT的透明窗口的变化,得出耦合光对EIT的影响大于探针光线宽的影响,这一结果将为原子存储时间的提高具有一定意义.     

Electromagnetically Induced Transparency in a Four-Level Atomic System

In this paper, we analyze and discuss the absorption properties of the probe beam in a four-level atomic system with a nearly hyper-fine doublet structure of two higher-lying excited levels based on electromagnetically induced transparency (EIT) for the two cases of transient process and steady-state process. The main gain of this work is to investigate theoretically the influence of the nearly hyper-fine levels on the probe absorption. For the transient process,using the numerical calculations by a simple Mathematica code we find that the magnitude of the probe absorption at the line center is small compared to the typical three-level atomic system in the context of electromagnetically induced transparency. For the case of the steady state, our results show that the probe absorption can be completely eliminated at the line center of the probe transition just as the usual three-level EIT scheme.     

利用非相干泵浦调控V型三能级系统的吸收与色散

理论研究了V型三能级系统中的吸收与色散特性,证明在探测光几乎无损耗的情况下可以实现超光速和亚光速传输。通过引入一束非相干泵浦场的作用,使输出探测光产生增益,并且在强耦合场诱导的Autler-Townes分裂(AT分裂)的情况下,可以得到探测光脉冲的增益抑制和相应的反常色散。     

微波射频场调制下Λ型三能级原子系统的电磁感应光栅

研究了在微波射频场调制下的Λ 型三能级原子系统的电磁感应光栅现象. 结果表明: 微波场可以增强对探测场的相位调制和增益作用, 使得衍射强度、尤其是一阶衍射强度明显提高; 当系统参数取值适当时, 一阶衍射强度随微波场强度呈指数增长的趋势. 关键词： 电磁感应光栅 电磁感应透明 微波射频场     

Electromagnetically Induced Transparency in a Four-Level Atomic System

In this paper, we analyze and discuss the absorption properties of the probe beam in a four-level atomic system with a nearly hyper-fine doublet structure of two higher-lying excited levels based on electromagnetieally induced transparency (EIT) for the two cases of transient process and steady-state process. The main gain of this work is to investigate theoretically the influence of the nearly hyper-fine levels on the probe absorption. For the transient process, using the numerical calculations by a simple Mathematica code we find that the magnitude of the probe absorption at the line center is small compared to the typical three-level atomic system in the context of electromagnetieally induced transparency. For the case of the steady state, our results show that the probe absorption can be completely eliminated at the line center of the probe transition just as the usual three-level EIT scheme.     

双模量子光场驱动的拉曼型光致离化系统中原子的相干俘获

研究了由双模量子光场驱动的拉曼型光致离化系统中原子的相干俘获性质，分析了反映原子－光场耦合性质的参量对系统相干俘获的影响，论证了在定的条件下，双模ＳＵ（２）相干光场可以将原子完全俘获。     

原子类原子系统光学特性的量子相干调控应用基础研究

简要介绍了在原子类原子小量子系统光学特性的量子相干调控应用基础研究方面所取得的一些成果,主要包括周期调制场控制弱光孤子传输、光学腔超窄线宽输出、非对称双量子阱中光学前驱波的分离以及极性分子系统中的电磁诱导透明现象等.     

开放简并二能级原子系统F_g=2F_e=1跃迁中的量子相干效应

文章分析了满足Fg=2Fe=1跃迁的开放简并二能级原子系统在磁场作用下的量子相干效应。该模型中,驱动场的偏振方向平行于磁场方向且与探针光偏振方向相互垂直。由于驱动场和塞曼分裂对原子的耦合作用,在不同驱动场拉比频率作用下将会分别出现电磁诱导透明(EIT)和电磁诱导吸收(EIA)效应,同时伴随相应的正常色散和反常色散。通过控制驱动场强度可以有效控制系统的量子相干效应,同时实现光速调控。     

闭合Λ型4能级系统中的电磁诱导透明和电磁诱导吸收

准Λ型4能级系统具有电磁诱导吸收(EIA)和电磁诱导透明(EIT)两种特性.准Λ型4能级系统包括两个基态精细结构能级和两个激发态精细结构能级,除光学耦合场和探测场外,附加了一个射频场作用于两个激发态精细结构能级之间.若对此系统进行拓展,在两个基态精细结构能级之间引入一个驱动场,则构成4场作用下的闭合Λ型4能级系统.本文对新引进的驱动场的作用规律进行了重点研究.研究结果表明,当驱动场和射频场的Rabi频率满足不同关系时,系统呈现EIA或EIT两种不同特性,探测吸收曲线的整体轮廓也随之改变.     

Entanglement of Non-symmetric Two Atomic Qubits Induced by a Coherent State Field

The entanglement of two atomic qubits, which are coupled to a coherent state field with different couplings, is studied. The dynamical evolution of the concurrence, which measures the degree of the entanglement between the two qubits, is plotted versus the scaled time gt. It is found that the two qubits can be entangled by the coherent state field even when they are initially prepared in the most mixed state, and for very weak field, the most mixed state can be more easily entangled than some pure states. It is also found that the entanglement between the qubits sensitively depends on the relative difference of the atomic couplings and the mean photon number of the field.     

Bell态原子与双模纠缠相干光场相互作用系统的原子布居数演化

运用全量子理论并结合数值计算方法,研究了处于Bell态的两个全同二能级纠缠原子与双模纠缠相干光场相互作用系统的原子布居数演化特性.讨论了双原子体系的初态、光场的平均光子数、双模纠缠相干光场的纠缠程度以及双原子体系的原子间耦合强度对原子布居时间演化的影响.结果表明:双原子体系的初态为|β11〉时,原子布居数不随时间变化;初态为|β00〉、|β01〉和|β10〉时,当初始平均光子数增大到一定数值时演化特性呈现出周期性的崩塌和回复效应,随初始光子数的增加时间演化曲线的振荡频率增大振幅减小,且初态为|β00〉或|β10〉时原子布居的回复周期是初态为时|β01〉的两倍;双模纠缠相干光场的纠缠程度以及原子间偶极相互作用的强弱对Rabi振荡频率没有影响但对振幅有着显著的影响.     

∧型四能级系统中的多重电磁诱导光透明研究

运用密度矩阵理论,研究了在外加相干耦合场作用下∧型四能级系统的吸收和色散特性。数值模拟表明：通过调节外加相干场的拉比频率强度,该系统可以单重、双重电磁诱导光透明现象,并在缀饰态表象中给出了定性解释。在双重电磁诱导透明现象中,透明窗的位置和吸收峰值可以通过调节外加相干场的失谐量来进行控制,而且透明点的位置可以连续变化。每个透明窗口在吸收最低时都伴随着高折射率,因此可以在此介质中实现超光速传播。     

调谐耦合场作用下的电磁诱导透明和增益

在通常的A型三能级系统中,耦合场和探测场分别与一对光学跃迁能级发生相互作用,使探测吸收曲线上出现线宽极窄的电磁诱导透明(Electromagnetically Induced Transparency,EIT)特性.本文采用调谐耦合场同时激励两个基态精细结构能级与激发态能级之间的跃迁,使系统同时呈现EIT和自发诱导相干...     

微波场对电磁诱导透明谱的局域调制

当用两个微波场作用到Λ型三能级原子的耦合跃迁的基态与另两个超精细能态构成的跃迁时,由微波场诱导产生的两个高对比度共振吸收线将单重电磁诱导透明谱分裂成三个透明窗口。通过调节微波场的强度或失谐量,可实现对原子透明谱进行局域调制。采用缀饰态理论对展示的物理现象进行了解释。这些研究对多通道光通信和原子的可控调制等方面有一定的作用。