Control of spontaneous emission in a five-level system

We study the control of spontaneous emission in a five-level atomic system driven by four fields. We show that with the variation of dynamical variables, namely, Rabi frequencies and carrier phases of driven fields, a wide variety of the spectral behavior can be obtained, including extreme spectral narrowing. Our system can be found easily in real atoms.     

Tunable interaction-free all-optical switching in a five-level atom-cavity system

A scheme is proposed for tunable all-optical switching based on the double-dark states in a five-level atom-cavity system. In the scheme, the output signal light of the reflection and the transmission channels can be switched on or off by manipulating the control field. When the control light is coupled to the atom-cavity system, the input signal light is reflected by the cavity. Thus, there is no direct coupling between the control light and the signal light. Furthermore, the position of the double-dark states can be changed by adjusting the coherent field, and,thus, the switching in our scheme is tunable. By presenting the numerical calculations of the switching efficiency,we show that this type of the interaction-free all-optical switching can be realized with high switching efficiency.     

五能级原子系统中的多重电磁感应透明

利用半经典理论,研究了在相干外场驱动下的倒三脚架型原子系统的吸收性质.数值计算结果表明:通过调节相干场的Rabi频率,该系统可以呈现出三重、双重、单重电磁感应透明;在三重电磁感应透明中,透明窗的位置可以通过调节相干场的失谐量来进行控制,而且透明点的位置可连续地变化,即在一定范围内存在一系列连续频率的探测光无吸收地通过介质.最后,在缀饰态表象中对上述现象给出了解释.     

Multi-wave mixing Autler-Townes splitting in the five-level atomic system

We have demonstrated the Autler-Townes (AT) splitting of the four-wave mixing (FWM) process and the six-wave mixing (SWM) process in an electromagnetically induced transparency (EIT) window in five-level atomic vapor of 87 Rb. Moreover we discuss interactions of multi-dressed states. The experimental results agree well with the theoretical analysis.     

Influence of self-phase modulation on coherent effects in five-level system

The possibility of formation of a coherent dark state in the five-level system in the entire volume of the medium in an adiabatic pulse propagation is investigated. It is shown that the dark state formation is independent on the value of the first two-photon detuning from the resonance, which may be changed during the propagation in the medium. In the case of the M-type system with the equal strengths of oscillators at the extreme transitions it is shown that the self-phase modulation does not influence the coherent effects while in the ladder-type system it may lead to the destruction of the dark state. The estimation of the length of the medium in which the propagation effects are negligible is obtained.     

Absorption and dispersion control in a five-level M-type atomic system

We investigate the steady optical response of a coherently driven five-level M-type atomic system in three different situations.When all three coupling fields have the same zero detuning,we just find one deep transparency window accompanied by a steep normal dispersion in the probe absorption and dispersion spectra.When two coupling fields are detuned from the relevant transitions to the same extent,however,a second deep transparency window may be observed in the presence of a narrow absorption line of linewidth ～50 kHz.In this case,two single-photon far-detuned transitions can be replaced by a two-photon resonant transition,so the five-level M system in fact reduces into a four-level quasi-Λ system.Finally,we note that no deep transparency windows and no narrow absorption lines can be found when all three coupling fields have unequal detunings.     

Polarization interference of multi-wave mixing in a confined five-level system

We investigated the coexisting four-wave mixing, six-wave mixing and eight-wave mixing in ultra-thin, micrometer and long cells. Such multi-wave mixing (MWM) processes can be modified by the polarization interference. The degree of destructive interference of atomic polarizations can be controlled by the wave vector, dressing field and cell length. Specifically, the oscillation behavior of intensity and linewidth of MWM signal results from the destructive interference in ultra-thin cell. For a doubly-dressed four-wave mixing, the inner dressing field suppresses the destructive polarization interference in micrometer and long cells, induces resonance enhancement. However, the outer dressing field only enhances destructive interference.     

Enhanced or suppressed six-wave mixing in a five-level atomic system

We show the enhancement and suppression of a six-wave mixing (SWM) signal in the electromagnetically induced transparency in a five-level ⁸⁵Rb atomic system. The results show the Autler—Townes splitting and the enhancement or suppression of SWM, which are caused respectively by a self-dressing effect and by an external dressing effect in the presence of mutual dressing between two SWM signals. In addition, we observe the polarization dependence of the enhancement and suppression of the SWM signals.     

五能级原子开放系统中的多波混频共存特性

研究了受强缀饰场作用的五能级原子系统所产生的多波混频共存特性.研究发现,通过调节激光束方向,沿同一方向出射的八波混频、双缀饰四波混频和单缀饰六波混频信号因共用能级的原子相干产生而出现竞争现象,通过控制缀饰场减弱四波混频和六波混频信号强度,可以达到增强八波混频信号的目的.还对级联和并联两种不同缀饰方式下双缀饰四波混频过程的差别进行了详细分析. 关键词： 双缀饰四波混频 单缀饰六波混频 八波混频 抑制增强     

Faraday rotation in a resonant five-level system via electromagnetically induced transparency

We study the Faraday rotation of polarization of a probe field in a cold, coherently driven five-level system with an M-type configuration. By means of a method of multiple scales we derive two coupled nonlinear envelope equations, which govern the evolution of two circularly polarized components of the probe field.It is shown that due to the quantum interference effect induced by two control fields, one can obtain a large rotation angle with a very low absorption of the probe field. In addition, an efficient control over the polarization state of the probe field in the system can also be easily realized.     

Atom localization via controlled spontaneous emission in a five-level atomic system

We investigate the one- and two-dimensional atom localization behaviors via spontaneous emission in a coherently driven five-level atomic system by means of a radio-frequency field driving a hyperfine transition. It is found that the detecting probability and precision of atom localization behaviors can be significantly improved via adjusting the system parameters. More importantly, the two-dimensional atom localization patterns reveal that the maximal probability of finding an atom within the sub-wavelength domain of the standing waves can reach unity when the corresponding conditions are satisfied. As a result, our scheme may be helpful in laser cooling or the atom nano-lithography via atom localization.     

N5B五能级系统中重复缀饰四波混频研究

从理论上研究了N5B五能级系统中一个激光场重复缀饰四波混频过程.结合能级图分析,从它特殊的Autler-Town分裂峰中可以非常清晰地看出其重复缀饰的作用.还研究了在强Probe场和强耦合场下N5B五能级下缀饰四波混频信号的抑制增强现象.采取独特的处理方法——独立作用法,研究结果表明一个激光场作用于N5B五能级系统时存在两次缀饰,并形成缀饰能级的二重分裂或者三重分裂,不同于多个耦合场对原子的多重缀饰作用.应用于非线性光谱术中对多峰结构的研究. 关键词： 四波混频 电磁感应透明 重复缀饰     

Controlled multi-wave mixing via interacting dark states in a five-level system

We theoretically investigate the controlled multi-wave mixing (MWM) via interacting multi-dark states in a five-level system. Four-wave mixing (FWM) with three kinds of dual-dressed schemes (nested, sequential, and parallel schemes), six-wave mixing (SWM) with the quadruply nested dressed, and eight-wave mixing (EWM) with the parallel combination of two nested dressed schemes coexisting synchronously in a multi-dressed electromagnetically induced transparency system were well described. Through investigating their spectra, we found that these multi-dressed-states induced by various dressed schemes show strong interaction and interchange. Investigations of these multi-dressing schemes and interactions are very useful for understanding and controlling the generated high-order nonlinear optical signals.     

Dual-dressed four-wave mixing and dressed six-wave mixing in a five-level atomic system

We study the co-existing four-wave mixing (FWM) process with two dressing fields and the six-wave mixing (SWM) process with one dressing field in a five-level system with carefully arranged laser beams. We also show two kinds of doubly dressing mechanisms in the FWM process. FWM and SWM signals propagatingalong the same direction compete with each other. With the properly controlled dressing fields, the FWM signals can be suppressed, while the SWM signals have been enhanced.     

Electromagnetically induced transparency and controllable group velocity in a five-level atomic system

The optical properties of a five-level atomic system composed of a A-type four-level atomic and a tripod four-level atomic systems are investigated. It is found that the behaviors of electromagnetically induced transparency (EIT) and group velocity can be controlled by choosing appropriate parameters with the interacting dark resonances. In particular, when all the fields are on resonance, the slow light at the symmetric transparency windows with a much broader EIT width is obtained by tuning the intensity of the coupling field in comparison with its sub-system, which provides potential applications in quantum storage and retrieval of light.     

Controlling the group velocity in a five-level K-type atomic system

The properties of a five-level K-type system are investigated. With the controlling fields, the properties of the dispersion and absorption of the system are changed greatly. The system can produce anomalous dispersion regions with absorption and normal dispersion regions with absorption or transparency. Furthermore, the group velocity can be varied from subluminal to superluminal by varying the intensity of the controlling field and the probe detunings in principle.     

Adiabatic transfer of population in five-level system in the absence of four-photon resonance

The influence of the nonzero four-photon detuning on the adiabatic transfer of population in five-level system has been studied both analytically and numerically. The estimations determining the permissible variation of the four-photon detuning have been obtained, which are well confirmed by numerical calculations.     

Dual-channel all-optical switching with tunable frequency in a five-level double-ladder atomic system

A scheme of five-level double-ladder-type atomic system is proposed with the aim of implementing dual-channel all-optical switching. Two transitions in the five-level atomic medium independently interact with the two orthogonally (circularly) polarized components from a weak linearly-polarized probe beam, while two other atomic transitions are coherently driven by a control beam and a switching signal beam. We demonstrate that the switching on/off of two orthogonally polarized beams at different frequencies can be achieved by adjusting the magnitude of the external magnetic field, which expands the frequency range of an optical signal switching operation and may improve its practicability.     

Influence of multiphoton detunings from resonance on adiabatic processes in a five-level system

The Schrödinger equation for a five-level system has been analyzed numerically for different values of multiphoton detuning from exact resonances. The range of admissible deviations for which the effect of multiphoton detunings on the eigenstate of the interaction Hamiltonian imitating a three-level system is insignificant has been determined. The effective population transfer and the possibility of double storage of optical information have been demonstrated.     

Electromagnetically-induced transparency in Doppler-broadened five-level systems

We study electromagnetically-induced transparency (EIT) of a probe field in a Doppler- broadened five-level K-type atomic system driven by three strong laser (coupling) fields. Effect of wave-vector mismatch occurring when the coupling field frequency is higher than that of the probe field frequency (λ _c < λ _p) are considered. Under the influence of the coherent coupling fields, the steady-state linear susceptibility of the probe laser shows that the system can have single or double or triple EIT windows depending on the amplitude and detuning of the coupling fields.