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     

Raman-enhanced nondegenerate four-wave mixing

The Raman-enhanced nondegenerate four-wave mixing (RENFWM) in benzene and methylbenzene was studied for five polarization geometries. One geometry gave suppression of the nonresonant background. A comparison between the experimental results and a theoretical curve has been made. From this, the transverse relaxation time of the dominant Raman modes in each liquid was obtained.Supported by the National Natural Science Foundation in China     

A tunable narrowband optical filter via phase conjugation by nondegenerate four-wave mixing in a doppler-broadened resonant medium

The formulation of phase conjugation via nondegenerate four-wave mixing in a Doppler-broadened resonant medium is generalized to include nondegenerate pump frequencies. This process is shown capable of yielding a tunable optical band-pass filter whose central frequency can be tuned over the entire Doppler profile with only a small degradation of the filter efficiency while still maintaining a bandwidth limited by the homogeneous linewidth.     

布里渊增强非简并四波混频

在CS₂介质中观测到由声波引起的布里渊增强非简并四波混频(NFWM)和由分子取向栅产生的瑞利型NFWM.研究发现,分子取向栅与声波之间并不是相互独立的,声波的存在会破坏瑞利型NFWM和布里渊增强NFWM极化之间的相位关系. 关键词： 四波混频 布里渊散射 瑞利散射     

双光子共振非简并四波混频测量Ba原子里德伯态的碰撞展宽和频移

采用双光子共振非简并四波混频测量了Ar缓冲气压引起的Ba原子里德伯6snd ¹D₂谱线系的碰撞展宽和频移, 计算了n=16---33的碰撞展宽截面和频移截面. 本方法是一种纯光学的测量技术, 当采用窄带激光器时可以获得里德伯态的消多普勒光谱. 与传统实验方法测量到的里德伯态纵向弛豫的碰撞展宽不同, 本方法可以研究碰撞引起的两能态间横向弛豫的展宽.     

Phase conjugation in biharmonically pumped two-photon resonant systems

Phase conjugation through four-wave mixing is considered in a two-photon resonant medium pumped by two distinct-frequency counter-propagating beams. This configuration eliminates the formation of stationary spatial holes. The relative magnitude of the pump intensities plays an important role and the phase-conjugation efficiency is found to be maximum for unequal values of the pump intensities.     

Phase conjugation under four-wave mixing on resonant and thermal nonlinearities at relatively high reflection coefficients

The dependences of the reflection (transmission) coefficients and the half-width of the spatial frequency band on the pump-wave intensity are obtained for an object (signal) wave in degenerate and quasi-degenerate four-wave mixers on resonant and thermal nonlinearities. The effect of the difference of the pump-wave frequencies on the phase-conjugation quality is studied at relatively high reflection coefficients.     

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     

Atomic coherence in nondegenerate four-wave mixing

Two-photon resonant nondegenerate four-wave mixing (NFWM) with the addition of a coupling field in Ba atomic vapour has been studied. We find that coherence of the atomic level transitions leads to suppression of the NFWM signal, giving rise to a dip with a linewidth that is linearly proportional to the intensity of the coupling field.     

Optical phase conjugation by resonant degenerate four-wave mixing in liquid phase medium

In this paper, frequency-doubled Nd:YAG laser's phase conjugation has been investigated experimentally using resonant degenerate four-wave mixing (DFWM). The iodine solution was used as resonant medium. In this way, the energy of the DFWM phase conjugation beam arrived at 43μJ/pulse while the total pump beam's energy reached 8mJ/pulse. The relation between the pulse energy of the DFWM phase conjugation beam and that of the pump beam was investigated. We also measured the optical field distributions of pump beam and DFWM phase conjugation beam, from which it can be noticed that the DFWM phase conjugation can improve the laser beam quality. At the same time, we observed the influence of the pump beam's disturbance on the DFWM signal.     

双光子共振非简并四波混频测量钡原子里德伯态碰撞展宽中的伴线研究

研究了采用双光子共振非简并四波混频技术测量原子里德伯态碰撞展宽时出现的伴线现象, 测量了不同缓冲气压下的钡原子里德伯态6snd ¹D₂ (n=16, 22, 36) 的四波混频谱线, 研究了伴线随主量子数n 的变化曲线以及伴线信号强度随缓冲气压压强的变化曲线, 分析了伴线对NFWM谱线的线宽的影响, 发现考虑伴线对四波混频谱线线宽的贡献, 可以对NFWM模型下测量到的碰撞展宽系数进行修正.     

Collinear nondegenerate four-wave mixing by a three-level system

Four-wave mixing in the vicinity of a sodium doublet is reported. The three-level system allows collinear phase-matching. The FWM is resonantly enhanced by a high gain on the blue side of the D₁ transition.Present address: LROL, Physics Department, Laval University, Quebec, Canada, G1K 7P4To whom correspondence should be addressed     

Phase conjugation in fluorescein film by degenerate four-wave mixing and holographic process

Phase conjugation is performed in a fluorescein film by a cw Ar ion laser of the wavelength 0.488 μm in a degenerate four-wave mixing (DFWM) configuration. It becomes apparent that the phase conjugate wave is generated simultaneously by not only DFWM but also a holographic process and that the DFWM and holographic components of the phase conjugate wave have different time constants.     

Level-splitting effects in resonant four-wave mixing

Resonant spectral structures of four-wave mixing (FWM) in molecular sodium are investigated. For a double- ? configuration with strong-weak-strong-weak fields, split components in FWM spectra induced by the strong pump fields are observed. It is shown that the split components merge into a single peak for a certain ratio of the strong field intensities. A correlation between the level-splitting effects and the saturation behavior of the FWM signal is experimentally demonstrated.     

Doppler-free two-photon spectroscopy using degenerate four-wave mixing

Using recently developed techniques of degenerate, four-wave mixing, Doppler-free two-photon spectra can be obtained. The signal level for such an experiment in xenon is calculated and found to be readily detectable as well as competing favorably with the method of observing fluoresence following two-photon absorption.     

Deflection of a phase-conjugate wave in nondegenerate four-wave mixing

The boundary problem for signal phase conjugation at nondegenerated four-wave mixing (FWM) is considered. In contrast to the statements of some authors it is shown that noncollinearity of the incident and the phase-conjugate waves occur. Expressions have been obtained for the deflection angle for a number of configurations of practical importance. Useful analogy between linear and nonlinear reflection at the FWM is noted.     

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.     

Rayleigh-type nondegenerate four-wave mixing: ultrafast measurement and field correlation

We report on an ultrafast longitudinal time measurement by a nonresonant Rayleigh-type nondegenerate four-wave mixing (NFWM). We investigated the field-correlation effects on Rayleigh-type NFWM by examining the time-delayed dependence of the NFWM spectra. Based on the field-correlation effects, a time-delayed method is proposed to suppress the thermal effect, and ultrafast relaxation time can be measured even in an absorbing medium.     

Nd:YAG激光在单晶硅中的四波混频相位共轭

以单晶硅作非线性介质,用调Q脉冲Nd:YAG激光作四渡混频,获得了相位共轭反射光波.从光激发电子-空穴对浓度及其所产生的相位光栅出发,理论计算了相位共轭镜的反射率.实验获得的共轭镜反射率为125%,并与实验中显示了其对相位干扰的补偿特性.     

Excitation of surface polaritons by nondegenerate four-wave mixing of evanescent waves

We propose a method for exciting a surface polariton wave by nonlinear mixing of three evanescent waves. The nonlinear polarization and phase matching conditions are analyzed for diatomic cubic crystals and a numerical example is given for GaP showing that this scheme is possible. Furthermore, by consideration of the energy balance in the crystal, the gain coefficient for the surface wave and the intensity of the wave coupled to the vacuum are also calculated.