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     

中间态引入量子干涉的三光子共振非简并六波混频

理论研究了五能级系统中三光子共振非简并六波混频(NSWM) 由于中间能级加入耦合光场而产生的量子干涉效应. 分析了耦合光场对三光子共振NSWM信号以及频谱的影响. 研究发现, 在强耦合场作用下, NSWM的频谱出现了Autler-Townes分裂, 它反映的是两个缀饰态的能级, 量子干涉可以使NSWM信号被抑制或增强. 提出利用量子干涉对NSWM信号产生增强作用, 可以由耦合场产生的缀饰态代替原子固有能级, 成为三光子共振的中间态, 从而控制耦合场来选择三光子共振的中间态的位置.     

受限原子极化相干缀饰四波混频光谱

研究了两电介质面间级联四能级系统原子的缀饰四波混频(FWM)光谱.在缀饰场的作用下FWM信号可产生Autler-Townes (AT)分裂,分裂所产生的峰及凹陷的线型及缀饰场对FWM信号的抑制与增强效应均受原子极化相干及受限原子与光场相互作用瞬态机制的调制.     

受限原子极化相干缀饰四波混频光谱

研究了两电介质面间级联四能级系统原子的缀饰四波混频(FWM)光谱.在缀饰场的作用下FWM信号可产生Autler-Townes (AT)分裂,分裂所产生的峰及凹陷的线型及缀饰场对FWM信号的抑制与增强效应均受原子极化相干及受限原子与光场相互作用瞬态机制的调制.     

引入量子干涉的双光子共振非简并四波混频

研究了级联四能级系统中双光子共振非简并四波混频(NFWM)由于加入耦合光场而产生的量子干涉效应，发现在强耦合场作用下NFWM频谱呈现AT劈裂，它反映的是两个缀饰态的能级.量子干涉还使NFWM信号被抑制或增强.此方法牵涉到三光子共振，因此可以成为研究原子或分子高激发态的有效光谱学工具. 关键词： 四波混频 量子干涉     

基于简并四波混频的双信道双频段增益谱

基于大规模光通信中频分复用的需求,本文以热原子的简并四波混频为模型,研究了具有双频段特性的双信道增益光谱.一束缀饰场诱导激发态能级发生分裂,由于量子干涉效应,四波混频信号的增益在双光子共振处被抑制,从而使增益谱线的包络由单频段转变为"M"型的双频段结构.同时,缀饰场还提高了相干基态的原子布居,进一步增强了四波混频信号的强度.最终实验上在铯原子气室内获得了一对具备双频段的双信道高增益光谱,并通过调节缀饰场的强度和频率失谐,实现了对双增益峰频率间隔的有效操控.     

光学外差法测量Ba原子的自电离态

提出了把三光子共振非简并六波混频(NSWM)和双光子共振非简并四波混频(NFWM)应用于研究Ba原子自电离态的光学外差探测方法。采用该方法测量了Ba原子的6P_３／２19d自电离态,并观察到了三光子共振 NSWM和双光子共振NFWM信号干涉引起的信号增强。该方法是一种纯非线性光学方法,具有优秀的空间分辨率和简单的光路。其中双光子共振非简并四波混频信号作为本地振荡光束,三光子共振非简并六波混频信号作为信号光束,通过 改变信号光束的频率来达到用光学外差探测法研究Ba原子自电离态的目的。该方法中,实现相位匹配所要求的条件不是很严格,可以在很宽的频率范围内实现相位匹配,而一般的六波混频很难做到相位匹配, 并且所测量的信号是相干光, 当用窄带宽的激光时,可以获得消多普勒的分辨率。     

泵浦光偏振对简并四波混频信号影响的实验研究

本文研究了Rb原子气室中泵浦光偏振对简并四波混频信号的影响.实验中,一束泵浦光和探针光沿相同方向传播进入Rb原子气室中,另一泵浦光沿反方向传播进入.通过改变泵浦光的偏振,观察四波混频信号的变化.实验结果表明:当两束泵浦光的偏振平行时,四波混频信号较强;当两束泵浦光的偏振相互垂直时,四波混频信号消失.理论分析表明泵浦光干涉导致的原子布居数差光栅是简并四波混频信号产生的原因.     

铷原子中参量六波混频和量子拍的研究

在铷原子中实现了轴向相位匹配的参量六波混频,并探测到位于红外光谱区的六波混频信号.六波混频信号与泵浦激光进行和频,产生了位于可见光范围内的可调谐的和频信号,并从和频信号中观察到频率为608 cm 1的量子拍.结果表明,六波混频信号中的量子拍能够用于研究原子和分子的相干特性.     

电磁诱导吸收和透明的可控切换

在一个非简并三能级梯型原子系统中,通过调谐探测场的强度,从理论和实验上研究了探测场通过铷原子蒸气的传输谱线。当探测场不再足够弱时,通过缀饰微扰链的方法推导了探测场响应的表达式并预言了电磁诱导吸收(electromagnetically induced absorption, EIA)的存在。实验上,在室温铷原子的D2线中,当弱探场状态切换到强探测状态时,不局限于单光子共振条件,电磁感应透明(electromagnetically induced transparency, EIT)向EIA的转换在探测场的不同失谐量处被实现。利用缀饰能级图分析了强的探测场和耦合场产生的二级缀饰态之间的相长干涉是EIA形成的主要原因。由于EIT和EIA的许多应用依赖于共振附近的异常色散,这个结果引入了控制色散符号的新能力。     

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.     

Spatial interference between four- and six-wave mixing signals

We experimentally demonstrate spatial interference between simultaneously generated four-wave mixing (FWM) and six-wave mixing (SWM) signals in a multilevel atomic system. By tuning the relative phase between the FWM and SWM processes the relative strengths between these two high-order nonlinear optical processes can be investigated.     

Coherent control of dressed images of four-wave mixing

In two-level as well as V-type three-level atomic systems, we study probe transmission, four-wave mixing (FWM) and fluorescence signals with dressing effect experimentally and theoretically. We find both the hyperfine structure (at the same energy level) and the transition dipole moment (at different energy levels) can affect the dressing effect. We also experimentally investigate that angle-control dynamics in the nonlinear propagation of the images of the probe and generated FWM in two-level atomic systems, and find that the focusing and defocusing of probe beam and FWM signals can be greatly affected by the angles between dressing fields.     

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.     

Opening four-wave mixing and six-wave mixing channels via dual electromagnetically induced transparency windows

Highly efficient four-wave mixing (FWM) and six-wave mixing (SWM) processes can coexist in a four-level Y-type atomic system due to atomic coherence. The simultaneously opened dual electromagnetically induced transparency windows in this four-level atomic system allow observation of these two nonlinear optical processes at the same time, which enables detailed studies of the interplay between the FWM and SWM processes. Three-photon and five-photon destructive interferences are also observed.     

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.     

Observation of two multiwave mixing processes via dual optical pumping channels

Based on double optical pumping channels,we experimentally study the competition between two coexistent six-wave mixing(SWM) processes falling into two electromagnetically induced transparency windows by scanning the frequency of the probe field in two similar five-level atomic systems of 85Rb.By blocking one optical pumping channel unrelated to the four-wave mixing(FWM) process,one SWM process,together with the FWM process,generated by a conjugated small-angle static grating could be observed in the spectrum.Moreover,the other SWM process obtained by blocking the first SWM channel is also observed together with the FWM process in a lower N-type four-level subsystem.These experimental results agree well with theoretical predictions.     

Enhancement and suppression of spatial splitting four-wave mixing in atomic medium

We experimentally report on the evolution from singly-dressed to doubly-dressed four-wave mixing (FWM) process by controlling the powers of the probe, the pump and the dressing fields respectively. The differences in the enhancement and the suppression of FWM signal between the two-level and cascade three-level atomic systems are observed and explained by the multi-dressed effect theoretically. Both the x direction and the y direction spatial splittings of the degenerate-FWM (DWFM) beams are obtained. We also investigate the switch between the enhancement and the suppression of the DWFM signals and between its spatial splittings in x direction and y direction. The spatial splittings in x direction and y direction can be controlled by the relative position and the intensity of the involved laser beams. Such a study can be useful for optimizing the efficiency of the FWM process and providing potential applications in spatial signal processing.     

Observations of Autler-Townes spatial splitting of four-wave mixing image

We report the self- and external-dressed Autler-Townes (A-T) splittings of the images of the generated four-wave mixing signal (FWM) and electromagnetically induced transparency (EIT) of probe images in cascade three-level atomic system. Such spatial properties of probe and FWM signals are induced by the enhanced cross-Kerr nonlinearity. We demonstrate the controlled electromagnetically induced spatial dispersion (EISD), splitting and focusing of probe and FWM signals images by adjusting self- and external-dressing fields. Studies on such controllable A-T spatial splitting and spatial EIT effect can be very useful in applications of spatial signal processing and optical communication.     

Interactions of Three Dual-Dressing Effects of Four-Wave Mixing in a Five-Level Atomic System

We study the four-wave mixing （FWM） in an opening five-level system with two dressing fields. There axe three kinds of doubly dressing mechanisms （parallel cascade, sequential cascade, and nested cascade） in the system for doubly dressed four-wave mixing. These mechanisms reflect different correlations between two dressing fields and different effects of two dressing fields to the FWM. Investigation of these mechanisms is helpful to understand the generated high-order nonlinear optical signal dressed by multi-fields.