基于双光子不对称色锁二阶随机关联的阿秒极化拍研究

基于两双光子过程的相位共轭二阶极化干涉，从理论上研究了四能级系统在阿秒量级的不对称和频极化拍频(FASPB).在抽运光束为窄带情形下，场关联对FASPB信号影响很弱.在宽带情形下，FASPB信号表现出共振-非共振交叉关联，双光子信号展现出混合辐射-物质失谐的THz阻尼振荡，即当激光频率偏离双光子共振跃迁的条件时，信号将呈现阻尼振荡，而且其双光子自相关信号的包络还呈现最大值零延时不对称.还研究了由于两双光子自相关过程零延时的偏差导致的阿秒拍频信号的不对称性，和两个双光子信号的最大值分别向相反的方向偏离零延时点的现象.FASPB作为一种阿秒超快调制过程，从理论上说它可以扩展到任何两偶极禁戒跃迁激发态的能级和系统. 关键词： 阿秒和频 极化拍 四能级 双光子     

非线性光学 位相共轭、自聚焦等相关效应

O4372006054150阿秒和频相位共轭极化拍频的不对称色锁二阶相干控制=Asymmetric second-order color-locking coherent controlof phase-conjugated attosecond sum-frequency polarizationbeats[刊,中]/余孝军(西安交通大学电子科学与技术系.陕西,西安(710049)),葛浩…//光学学报.—2006,26(6).—953-960研究了级联三能级系统中孪生色锁随机光场的相位共轭阿秒和频极化拍频(ASPB)不对称新效应。从理论上分析了自关联单光子简并四波混频(DFWM)和双光子非简并四波混频(NDFWM)信号辐射场与物质间不对等效应、混合型太赫兹失谐振荡特性,…     

倒V形四能级亚飞秒极化拍的三光子吸收和色散

基于孪生色锁噪声场的互相关效应，从理论上研究了倒V形(RV)四能级飞秒量级差频极化拍与极化拍中五阶非线性极化率，并提出了用一种相位敏感的方法来研究多能级原子相干造成的三光子六波混频过程.在抽泵光束为窄带末端情况下，场关联对信号和极化率的影响都很弱，在非窄带情况下，场关联会使极化强度自相干信号和极化拍信号产生关于零延时的不对称性和时域扫描上的辐射与物质失谐阻尼振荡(RDO)，而极化率会产生频域扫描上的RDO振荡.参考光信号是一路传播方向和六波混频信号稍有区别的双光于非简并四波混频信号.五阶非线性响应则由享生     

倒V形四能级亚飞秒极化拍的三光子吸收和色散

基于孪生色锁噪声场的互相关效应,从理论上研究了倒V形(RV)四能级飞秒量级差频极化拍与极化拍中五阶非线性极化率,并提出了用一种相位敏感的方法来研究多能级原子相干造成的三光子六波混频过程.在抽泵光束为窄带末端情况下,场关联对信号和极化率的影响都很弱,在非窄带情况下,场关联会使极化强度自相干信号和极化拍信号产生关于零延时的不对称性和时域扫描上的辐射与物质失谐阻尼振荡(RDO),而极化率会产生频域扫描上的RDO振荡.参考光信号是一路传播方向和六波混频信号稍有区别的双光于非简并四波混频信号.五阶非线性响应则由享生 关键词： 外差法 吸收 色散 非线性极化     

缀饰原子系统中双光子共振非简并四波混频

本文研究了缀饰原子系统中的双光子共振非简并四波混频.理论上我们研究了多普勒增宽的四能级系统中耦合光场对双光子共振非简并四波混频的影响,发现加入强耦合场后,非简并四波混频频谱出现Autler-Townes分裂;在不同双光子共振失谐时,由于量子干涉双光子共振非简并四波混频的信号能够被抑制或增强.实验上我们在Ba原子蒸汽中,通过引入基态6s2和自电离里德堡态6pnd之间的原子相干证实了该现象.本方法提供了一种不仅可以测得共振频率和横向弛豫,而且可以测得两个高激发原子态之间的跃迁的偶极矩阵元的新的光谱学工具.     

阿秒极化拍的V型三能级对称二阶相干理论

基于两单光子过程的相位共轭二阶极化干涉，从理论上研究了V型三能级系统在阿秒量级的对称和频极化拍频（SFPB），考虑了抽运光束为窄带线宽或宽带线宽的情形，发现测得的信号对任意带宽的马可夫随机光场的统计特征非常敏感，其在测量偶极禁界跃迁两激发态之间的能级和时并不受激光线宽的限制，仅取决于光学跃迁均匀增宽，而且可以得到消除多普勒增宽的测量精度.在窄带情形下，场关联对SFPB信号影响很弱.在宽带情形下，SFPB信号表现出共振 非共振交叉关联.SFPB作为一种阿秒超快调制过程，从理论上说它可以扩展到任何和频能级系统. 关键词： 阿秒 和频 极化拍 二阶相干     

简并四波混频中的能级交叉效应

我们用微扰方法计算了近简并准二能级系统的三阶非线性极化率x⁽³⁾(-ω;ω,ω,-ω)。研究了简并四波混频的能级交叉效应,并与共振荧光的能级交叉效应比较。指出简并四波混频的能级交叉效应可用来测量上能级及下能级的弛豫速率。 关键词：     

应用双光子共振非简并四波混频测量Ba原子里德伯态

使用具有中间态的双光子共振非简并四波混频(NFWM)测量了Ba原子J＝0和J＝2的偶宇称里德伯线系，与现代实验方法不同，本方法是纯光学的方法，其光路简单，检测的是相干光，而不是电子或离子信号.当用窄带宽的激光时，本技术对里德伯能级的窄光谱结构可以获得消多普勒的分辨率. 关键词： 四波混频 里德伯态     

应用双非简并四波混频理论研究原子的碰撞效应

在己有实验的基础上,提出了由双光子共振非简并四波混频和碰撞再构非简并四波混频组成用于研究原子碰撞效应的双非简并四波混频理论,分析了缓冲气压、温度、共振失谐和碰撞展宽系数对双非简并四波混频谱线的影响.在由基态、中间态和激发态组成的级联三能级系统中,双非简并四波混频可同时研究碰撞引起的激发态谱线展宽和碰撞引起的中间态能级再分布现象.与测量纵向弛豫碰撞展宽的传统实验方法不同,本文方法是一种纯光学的相干测量技术,可以同时测量激发态与基态间的横向弛豫Γ_(20)和中间态与基态间的横向弛豫Γ_(21)的碰撞展宽.     

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。     

Fifth-order attosecond polarization beats using twin color-locked noisy lights in cascade three-level system with Doppler-free approach

Fifth-order attosecond sum-frequency polarization beat (FASPB) is studied in a cascade three level system with the phase-conjugation fourth-order coherence function theory. An improved schematic diagram of geometry, which is different from that inducing fifth-order femtosecond different-frequency polarization beat(FFDPB), is used to obtain FASPB. By analyzing the cases that pump beams have either narrow or broad bandwidth, it is found that the temporal behavior of the sum-frequency polarization beat signal depends on the properties of the lasers and transverse relaxation rate of the atomic energy-level system. Finally,the cascaded four-wave mixing (FWM) processes and the difference between attosecond and femtosecond polarization beats have been discussed, it is found that cascaded or sequential lower processes can often obscure the direct fifth-order polarization beat processes.     

Polarization entanglement generation at 1.5 μm based on walk-off effect due to fiber birefringence

In this Letter, a linear scheme to generate polarization entanglement at 1.5 μm based on commercial polarization maintained dispersion shifted fiber (PM-DSF) is proposed. The birefringent walk-off effect of the pulsed pump light in the PM-DSF provides an effective way to suppress the vector scattering processes of spontaneous four-wave mixing. A 90 deg offset of fiber polarization axes is introduced at the midpoint of the fiber to realize the quantum superposition of the two correlated photon states generated by the two scalar processes on different fiber polarization axes, leading to polarization entanglement generation. Experiments of the indistinguishable property on single-side and two-photon interference in two nonorthogonal polarization bases are demonstrated. A two-photon interference fringe visibility of 89±3% is achieved without subtracting the background counts, demonstrating its great potential in developing highly a efficient and stable fiber based polarization-entangled quantum light source at the optical communication band.     

Polarization insensitive wavelength conversion based on dual-pump four-wave mixing for polarization multiplexing signal in SOA

We have theoretically investigated polarization insensitive all-optical wavelength conversion for polarization multiplexing signal based on dual-pump four-wave mixing (FWM) in a SOA. The simulation result shows that the polarization insensitive converted signal can be separated into two lightwaves without crosstalk when one of the two orthogonal data lightwaves is parallel with one pump and the SOA should be polarization insensitive. Several conditions which affect the conversion efficiency for polarization multiplexing signal are also discussed.     

Coexisting Raman- and Rayleigh-Enhanced Four-Wave Mixing in Femtosecond Polarization Beats

Based on the polarization interference of Raman- and Rayleigh-enhanced four-wave mixing processes, heterodyne detection of the Raman, Rayleigh and coexisting Raman and Rayleigh femtosecond difference-frequency polarization beats is investigated in the cw and the three Markovian stochastic models, respectively. These two processes exhibit asymmetric and symmetric spectra, respectively, and the thermal effect in them can be suppressed by field-correlation method. Such studies of coexisting Raman- and Rayleigh-enhanced four-wave mixing processes can have important applications in coherence quantum control, and quantum information processing.     

汞蒸汽中双光子共振四波和频产生125nm的相干辐射

利用汞原子6~1S_0—7~1S_0双光子共振四波和频产生了125nm的相干辐射.对双光子共振增强效应、双光子共振克尔(Kerr)效应进行了研究.讨论了平面波和聚焦情况下最佳相位匹配的条件.实验中还观测到了四波参量振荡和四波差频的信号输出.     

Coherent Phase Control of Ultrafast Polarization Beats in Reverse V-Type Three-Level System

We investigate the third-order nonlinear absorption and dispersion of femto- and atto-second polarization beats between the one-photon degenerate four-wave mixing process and the two-photon nondegenerate four-wave mixing process in the pure homogeneously-broadened reverse V-three-level using twin noisy fields. The third-order nonlinear response can be controlled and modified by the colour-locked correlation of twin noisy fields. Most importantly, the coherent phase control in optical heterodyne detection for studying the phase dispersion of the third-order susceptibility is demonstrated. The radiation-matter detuning oscillation is also considered in the freauencv domain.     

Beat structure in spectrally resolved four-wave mixing under crosslinear polarization in GaAs quantum wells

The polarization dependence of beat structure in spectrally resolved four-wave mixing was investigated on 50 Å GaAs multiple quantum wells. Under crosslinear polarization we observed a beating structure at higher energy region of the main spectral peak due to biexciton–exciton transition. The beat has a period of 0.95 ps and is constructive at delay time T=0 ps, which suggests the corresponding double Feynman diagrams to be of the same type. By shortening the central wavelength of the sub-ps laser, we observed the distinctive peak corresponding to the beat period. Even in GaAs system, which is generally believed to have a small biexcitonic effect, there are two effective 2-exciton states with well-defined energies which are required to describe the third-order optical nonlinearly.     

Dressed multi-wave mixing in a V-type four-level atomic system

The dressed four- and six-wave mixings in a V-type four-level system are considered. Under two different dressed conditions, two- and three-photon resonant Autler--Townes splittings, accompanied by enhancement and suppression of wave mixing signal, are obtained analytically. Meanwhile, an electromagnetic induced transparency of multi-wave mixing is presented, which shows multiple peaks and asymmetric effects caused by one-photon, two-photon and three-photon resonances, separately. The slow light propagation multiple region of multi-wave mixing signal is also obtained.