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.     

Propagation of Light in an Ensemble of Tripod Level Atoms

We study the propagation of a quantum probe light in an ensemble of tripod level atoms when the atoms are coupled to two other classical control fields. First we calculate the dispersion properties, such as susceptibility and group velocity, of the probe light within such an atomic medium under the case of three-photon resonance via the dynamical algebra method of collective atomic excitations. Then we calculate the dispersion of the probe light in the case that two classical control fieMs have the different detunings to the relative atomic transitions. Our results show that in both cases the phenomenon of electromagnetically induced transparency can occur. Especially under the second case, we can find two transparency windows for the probe light.     

Propagation of Light in an Ensemble of Tripod Level Atoms

We study the propagation of a quantum probe light in an ensemble of tripod level atoms when the atoms are coupled to two other classical control fields. First we calculate the dispersion properties, such as susceptibility and group velocity, of the probe light within such an atomic medium under the case of three-photon resonance via the dynamical algebra method of collective atomic excitations. Then we calculate the dispersion of the probe light in the case that two classical control fields have the different detunings to the relative atomic transitions. Our results show that in both cases the phenomenon of electromagnetically induced transparency can occur. Especially under the second case, we can find two transparency windows for the probe light.     

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.     

Coherently induced grating in refractive index enhanced medium

We demonstrate a scheme for coherently induced grating based on a mixture of two three-level atomic species interacting with two standing-wave fields. As a result of interaction between the absorptive and amplified Raman resonances, the refractive index of the medium can be enhanced and modulated periodically. Then a sinusoidal grating, which can diffract the probe field into high-order directions, is coherently formed in the medium. The proposed scheme is theoretically investigated in a mixture of atomic isotopes of rubidium. The results show that the diffraction efficiency depends strongly on the two two-photon detunings of the two Raman transitions and the intensities of the two driving standing-wave fields.The proposed electromagnetically induced grating scheme may be applied to the all-optical switching and beam splitting in optical networking and communication.     

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     

∧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。     

电磁诱导吸收介质中探针场的量子噪声特性

在N型原子系统中,在二束强的耦合场作用于介质对探针场体现出很强的诱导吸收作用,与此同时,强吸收引起的自发辐射噪声会影响探针场的量子噪声特性.该文章研究了输入的量子化探测场在经过电磁诱导吸收介质后的噪声特性变化,数值模拟得出,通过调节控制场的强度可以使得探测场的噪声谱图形在吸收窗口范围内产生震荡分裂,噪声最小值处于一定的探针场失谐处.     

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.     

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.     

Comparative Study of Light Manipulation in Three-Level Systems Via Spontaneously Generated Coherence and Relative Phase of Laser Fields *

We present a comparative study of the control of-group velocity in three-level atomic systems including $\Lambda{}$-, Ladder-, and-V-types via spontaneously generated coherence (SGC) and relative phase of laser-fields. In the steady regime, expressions of group index are derived as an-analytical function of controllable parameters related to SGC and relative phase.-It is shown that the group velocity can be further slowed down or speeded up-under SGC in which modifications of group velocity due to the SGC in $\Lambda{}$--and V-systems are stronger than that in Ladder-system. In particular, when-interference strength of SGC p increases from 0.7 to 1.0, the light-propagation is switched from superluminal to subluminal modes (for $\Lambda{}$--and Ladder-systems) or from subluminal to superluminal modes (for V-system). In-the presence of relative phase, the group velocity changes between subluminal and-superluminal modes with a period of 2$\pi{}$. In resonant region, the largest-positive value of group index reaches at the relative phase $\varphi{}$ = $\pi{}$-while the largest negative value of group index reaches at $\varphi{}$ = 0 and-2$\pi{}$ for the $\Lambda{}$- and Ladder-systems, otherwise, for the V-system the-largest positive group index occurs at $\varphi{}$ = 0 and 2$\pi{}$, and the largest-negative group index occurs at $\varphi{}$ = $\pi{}$.     

Broadband Plasmon-Induced Transparency to a Electromagnetically Induced Absorption Conversion Metastructure Based on Germanium

A Germanium (Ge) metastructure with switching features from broadband plasmon-induced transparency (PIT) and electromagnetically induced absorption (EIA) is presented, which forms a broadband PIT through the near-field coupling between the localized plasmon resonance and the Mie resonance employing four gold cut wires as bright plasmon resonators and four C-shaped dielectric rings as dark plasmon resonators. A wide transparent window above 0.9 is achieved covering from 0.622 to 0.823 THz with a relative bandwidth of 27.8%. In addition, through phase modulation, a magnetic dipole is generated by the constructive interference of the near-field coupling of the three resonators to realize the PIT to EIA conversion. In addition, a grid-like metastructure is introduced to realize the PIT to EIA conversion by phase modulation. To enhance the EIA bandwidth, another layer of C-shaped reflection plate resonator is introduced to increase the dark mode loss, and a layer of frequency selective surface composed of cross-shaped resonators is also used. Thus under the dual effect, a wide absorption window above 0.75 is achieved covering from 0.647 to 0.756 THz with a relative bandwidth of 15.5%.     

光学-射频双光子耦合作用下的电磁诱导透明和电磁诱导吸收

在通常的Λ型三能级系统中,光学耦合场和探测场分别激发两个不同的光学跃迁,探测吸收谱呈现电磁诱导透明(EIT)特性.若将此系统拓展为光学-射频双光子耦合场和探测场共同作用下的准Λ型四能级系统,探测吸收谱呈现电磁诱导吸收(EIA)和EIT两种特性.通过求解系统的密度矩阵方程,分析了EIA和EIT的产生条件,并给出了相应的缀饰态解释.研究结果表明,在准Λ型四能级系统中,光学耦合场对EIA和EIT的形成起决定作用,共振时出现EIA,非共振时出现EIT,而且EIA和EIT的线宽随着光学耦合场拉比频率的增大而增加. 关键词： 电磁诱导透明 电磁诱导吸收 射频场 光学耦合场     

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.     

Preparation of Steady 3D Dark State Entanglement in Dissipative Rydberg Atoms via Electromagnetic Induced Transparency

A scheme to prepare a 3D entangled state between a pair of Rydberg atoms via dissipative dynamics and electromagnetic induced transparency associated with the single-atom dark state is proposed. The prepared entangled state is the dark state of the whole system. The scheme is also feasible regardless of initial purity or mixed state. Since the proposed scheme is based on the Rydberg block regime, the Rydberg–Rydberg interaction strength does not need to satisfy a certain relation with laser detuning, which is very different to the Rydberg-antiblock-based dissipative schemes. One group of Rydberg states and corresponding parameters to simulate the fidelity are used, which verify the feasibility of the scheme.     

准Λ型四能级原子系统在弱场中的增益及电磁感应透明

利用数值模拟的方法讨论了稳态下准型四能级原子与两光场相互作用系统对探测场的增益以及与粒子数布居规律之间的关系。结果表明即使在场较弱的情况下,随着探测场和它所对应能级间跃迁频率失谐量的变化,系统在所有拉比频率相位为零时对探测光总会同时呈现三个增益峰和两个固定的产生电磁感应透明(EIT)现象的位置,并且当系统呈现电磁感应透明的同时,探测场所对应的高能级粒子数为零;而拉比频率相位的变化则会导致系统对探测光既有吸收也有增益,并且也呈现电磁感应透明现象,但仅仅相位的变化并不影响高能级的粒子数分布。值得注意的是该结果均在精确求解下所得。     

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 thecoupling transition in the five-level K-type atom with another higher excitedlevel, the two-photon electromagnetically induced transparency can belocally modulated by altering the parameters of the additional perturbationfield. With different detunings of the coherent perturbation field, theabsorption peak or transparency window with sharp and high-contrast spectral feature can be generated in the two-photon absorption spectrum. The physical interpretation of these phenomena is given in terms of the dressed states.     

Transient Dynamics of Light Propagation in A-Atom EIT Medium

We investigate the transient phenomenon or property of the propagation of an optical probe field in a medium consisting of many A-type three-level atoms coupled to this probe field and a classical driven field. We observe a hidden symmetry and obtain an exact solution for this light propagation problem by means of the spectral generating method. This solution enlightens us to propose a practical protocol implementing the quantum memory robust for quantum decoherence in a crystal. As a transient dynamic process this solution also manifests an exotic result that a wave-packet of light will split into three packets propagating at different group velocities. It is argued that “super-luminal group velocity” and “sub-luminal group velocity” can be observed simultaneously in the same system. This interesting phenomenon is expected to be demonstrated experimentally.     

Transient Dynamics of Light Propagation in A-Atom EIT Medium

We investigate the transient phenomenon or property of the propagationof an optical probe field in a medium consisting of many A-type three-level atoms coupled to this probe field and a classical driven field. We observe a hidden symmetry and obtain an exact solution for this light propagation problem by means of the spectral generating method. This solution enlightens us to propose a practical protocol implementing the quantum memory robust for quantum decoherence in a crystal. As a transient dynamic process this solution also manifests an exotic result that a wave-packet of light will split into three packets propagating at different group velocities. It is argued that “super-luminal group velocity“ and “sub-luminal group velocity“ can be observed simultaneously in the same system. This interesting phenomenon is expected to be demonstrated experimentally.