光学-射频场双驱动原子系统中的透明与吸收特性的调控

光与物质的相互作用可以产生许多奇特的量子光学现象,电磁诱导透明和电磁诱导吸收是其中最典型的现象.本文在通常的Λ型三能级系统中引入射频场作用于激发态的精细结构能级之间,组成光学-射频双驱动场共同激发原子的相干跃迁,使系统的吸收特性出现电磁诱导透明和电磁诱导吸收两种量子相干效应.通过讨论双驱动场开启后直到系统达到稳定的量子相干过程,分析电磁诱导透明和电磁诱导吸收随时间的产生和转化,得到两种量子相干现象之间的关联性及对其进行量子调控的方法.     

光场驱动下退化的级联三能级原子中的量子相干效应

研究了退化的级联三能级原子在施加静磁场后的量子相干效应,系统既可出现单光子电磁诱导透明,也可出现双光子电磁诱导透明以及双光子电磁诱导吸收,这取决于两个驱动场的拉比频率和塞曼分裂的相干性。 Quantum coherence effects in degenerate cascade three-level atom subject to magnetic field are investigated. One-photon EIT, two-photon EIT and two-photon EIA are obtained, due to the coherence between the drive Rabi frequency and Zeeman splitting.     

量子调控中介质的左手效应

研究了准Λ型四能级原子与多模光场相互作用的量子系统.在量子干涉机理下,原子的相对介电常数和相对磁导率受相干光场诱导发生显著变化,在合适的参数区间内,它们同时出现负值,即产生了左手效应. 关键词： 量子干涉 左手效应 电磁诱导 负折射率     

空场诱导相干性对倒转Y型四能级原子系统中单光子和双光子吸收性质的影响

当倒转Y-型四能级原子的两基态能级邻近简并时,连接基态的两个跃迁路径与同一个真空场辐射场相互作用导致的量子干涉效应便产生了空场诱导相干性.空场诱导相干性能使倒转Y-型四能级原子在共振点的单光子和双光子电磁诱导透明现象减弱,而在其他失谐量处产生单光子增益现象。同时,外加相干光场的相对相位对原子的吸收性质有重要的影响.     

简并能级系统中的量子相干效应与暗态

文章分析了简并二能级原子系统Fg=1→Fe=0中的吸收、色散特性与暗态的对应关系,比较了双Λ型和Λ型能级结构下的量子相干效应.结果表明,双Λ型系统中多个基态相干性会增强原子相干特性.     

耦合场线宽：抑制电磁诱导吸收

原子相干对吸收的相长干涉导致电磁诱导吸收，这是一类新的相干效应. 以三个电偶极跃迁构成N型链，中间跃迁作为探测跃迁的四能级系统为例，揭示耦合场线宽抑制电磁诱导吸收的强度. 这并非与电磁诱导透明系统中耦合场线宽产生或者增强吸收的情形相矛盾，线宽仍然是抑制系统的相干性. 关键词： 电磁诱导吸收 耦合场线宽 原子相干 退相干     

激光场线宽对电磁诱导吸收效应的影响

采用密度矩阵方程,在引入激光场线宽的条件下,计算了三个电偶极跃迁构成N型四能级系统中介质对探测场的吸收,从而研究激光场线宽对电磁诱导吸收效应的影响.结果表明:随着激光场线宽增大,原子相干将会减弱,从而抑制电磁诱导吸收.     

多窗口可调谐电磁诱导透明研究

当两束激光以Λ-构型作用于三能级原子系统并满足双光子共振条件时，探测激光场吸收谱呈现电磁诱导透明(EIT)特征.若再加一个微波控制场作用于该三能级系统的两个低能级跃迁之间，会导致探测吸收特性明显变化，EIT窗口将发生劈裂.通过求解相应的密度矩阵方程，揭示了外加微波场作用下EIT窗口的变化规律，并给出了相应的缀饰态解释.研究结果表明，在适当的条件下, 电磁诱导透明呈现三重结构，而EIT窗口的频率位置取决于微波控制场的拉比频率及频率失谐量.因此通过改变微波控制场的参数可以实现多EIT窗口的频率调谐. 关键词： 电磁诱导透明 量子相干 频率调谐 多窗口EIT     

微波场驱动下V型三能级原子的吸收和色散特性

当用微波场作用到V型三能级原子的两个激发态能级时,系统跃迁路径之间发生交叉耦合导致了量子相干效应.通过调节微波场的强度,可实现对原子吸收和色散性质的改变,并呈现零吸收高折射率现象.此外,微波场诱导的量子相干也可实现相对相位对探测光增益的控制.     

微波场驱动下V型三能级原子的吸收和色散特性

当用微波场作用到V型三能级原子的两个激发态能级时,系统跃迁路径之间发生交叉耦合导致了量子相干效应.通过调节微波场的强度,可实现对原子吸收和色散性质的改变,并呈现零吸收高折射率现象.此外,微波场诱导的量子相干也可实现相对相位对探测光增益的控制.     

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.     

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: Answering a Question of Romain

At the request of Romain, I derive analytical results describing the response of a three-level medium subjected to a strong pump beam and two weak probe beams. All three beams have a constant intensity. The results are the real and imaginary parts of the medium coherence, which is related to the nonlinear susceptibility. The main feature is that the three beams mix absorption and dispersion. There is a finite window of gain bounded by a point of electromagnetically induced transparency. This revised version was published online in July 2006 with corrections to the Cover Date.     

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.     

Plasmon-induced absorption in stacked metamaterials based on phase retardation

In this paper, based on the constructive interference of plasmonic dipolar and quadrupolar modes, a classical analogue of electromagnetically induced absorption （EIA） is demonstrated theoretically in a stacked metamaterial consisting of a short metal strip （which acts as a bright resonator） and a long metal strip （acting as a dark resonator）, which has been reported to support the electromagnetically induced transparency （EIT） effect. The transition from EIA to EIT can be clearly observed in the absorbance spectra via varying the vertical spacing between two resonant oscillators. With the help of the coupled two-oscillator model, the phase shift between the bright and dark resonance modes is calculated by fitting the simulated absorbance spectra, which reveals the physical mechanisms behind constructive and destructive interference effects in EIT/EIA metamaterials.     

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.     

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。     

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     

Quantum coherent effects in multi-Zeeman-sublevel atomic systems

This paper reports the experimental results on electromagnetically induced absorption （EIA） spectra observed in the system which does not satisfy completely the conditions given by Lezama et al [1999 Phys. Rev. A 59 4732]. EIA signals on the transitions in the Cs D2 line are able to be observed, where Fg ←→ Fe = Fg-1 as open systems. Theoretical model of Lezama et al is good for the case Fg ←→ Fc = Fg ＋ 1, considering spontaneous transfer of atomic coherences or populations this model is not able to explain our experimental results obtained in the case Fg ←→ Fe = Fg - 1. This paper offers a theoretical model which is able to well explain the case Fg ←→ Fc = Fg - 1. It also uses this theoretical model to explain the split and shift of EIA peaks, which have been obtained in experiments.     

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.