Mn：KNSBN晶体中弱入射光高反射率四波混频相位共轭

功率为1mW左右的He-Ne激光束在Mn:KNSBN晶体中实现四波混频相位共轭。入射光相对于晶体主光轴的取向及入射光偏振组态对相位共轭反射率都有很大的影响。当物光近于布儒斯特角入射时,反射率可达60％。建立时间约为60sec的光折变光栅具有18hr左右的寿命。晶体中观察到诱导四波混频相位共轭。     

Zn∶Fe∶LiNbO_3晶体二波耦合和相位共轭效应的研究

采用二波耦合和四波混频实验,研究了Zn:Fe:LN(Fe:0.03wt.%,Zn:5.0mol)晶体的光折变二波耦合衍射效率和长时间照射下透射光强随时间的动态变化行为,以及其相位共轭效应,分别测试了其二波耦合衍射效率和其相位共轭反射率,结果表明该晶体的衍射率可达到56%,且其衍射效率随着其信号光的减小先增大后减小,相位共轭反射率随信号光的增大呈减小的趋势,最高共轭反射率可达到650%。     

Saturable absorbers for low power optical phase conjugation

Properties of a few saturable absorbers as candidates for low power optical phase conjugation (OPC) are examined. The specific systems studied are the dyes eosin, erythrosin B and Rose Bengal, doped in gelatin, polyvinyl alcohol and boric acid glass films. A method for quickly checking saturated absorption is suggested and demonstrated. Examples for OPC with these systems are cited and limitations are briefly discussed. An erratum to this article is available at .     

用于实现散射介质中时间反演的数字相位共轭的相干性

抑制散射介质对光的散射,调控光在散射介质中的传输,是光通信、生物光子学、光镊等领域的重要课题.设计并实现了基于宽谱光源和数字相位共轭的可调控光在散射介质中传输的时间反演实验系统.实验获取了不同相干长度下物光和参考光束之间的光程差与干涉图样、相位图及时间反演信号之间的关系,分析了光源相干性对调控光在散射介质中传输的影响.实验结果表明,基于宽谱光源的相干特性和数字相位共轭技术,通过调节光程差能选择性获取同一散射角度及相同传输路径的光束的相对相位,再利用空间光调制器对参考光束进行调控,实现光束的反向传播,从而选择性实现对同一散射角度及相同传输路径的光的时间反演.     

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.     

Dynamic holography in alkali metal vapour

Problems of dynamic hologram recording on resonant absorption lines of alkali metal vapour are discussed. Light beams and media parameters are determined that are necessary for hologram recording with usable efficiency. The effects of thermal atomic motion and the radiative transport of excitation influence on the spatial frequency transfer function of two-level media are investigated. Results of hologram recording in vapour of Rb (780.0 nm) and Cs (852.1 nm) using low-power CW-lasers are presented. Transmission holograms in the volume media and reflection holograms near the boundary of the resonant vapour and the dielectric are compared. For transmission holograms the advantage of collinear read-out when using pure vapour in comparison with a counterpropagating read-out is shown, and this makes it possible to achieve higher values of hologram efficiency over a wide range of atomic density. It is shown that reflection hologram recording is characterized by higher resolution, as compared with hologram recordings in the volume of extended media. Problems of metal vapour hologram usage for laser parameter control are discussed. The feasibility of holograms in Cs-vapour usage as a spectral-selective real-time feedback element in a semiconductor laser external cavity is shown.     

Theoretical study on phase conjugation in weakly injected vertical-cavity surface-emitting lasers

This paper gives a detailed theoretical investigation on phase conjugation induced by nearly degenerate fourwave mixing in single mode vertical-cavity surface-emitting lasers （VCSELs） with weak optical injection. Considering VCSELs that can work in linearly polarized or elliptically polarized states, it derives the theoretical expression of the conjugated field by small signal analysis based on the vectoral rate equations-the spin-flip model. For linearly polarized state, VCSELs show similar conjugate spectra to edge-emitting semiconductor lasers. For the elliptically polarized state, dichroism and birefringence parameters as well as the spin-flip rate can change the conjugate spectra. Especially, when frequency detuning of the probe and pump waves is between the positive and negative relaxation oscillation frequency, changes are evident. For specific values of parameters, conjugate efficiency between 20 dB to 40 dB are obtained.     

Coexistence of Self-pumped Phase Conjugation and Mutual-pumped Phase Conjugation in Ce:BaTiO3

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布里渊增强四波混频时域特性的理论研究

通过对布里渊增强四波混频(BEFWM)瞬态耦合波方程的数值求解，描述了共轭输出光的时域调制行为.同时，对能量耦合过程中起决定性作用的声学波的时空演化特征进行了模拟与分析，由此给出BEFWM时域特性物理机理的解释.研究表明，共轭光输出强度的波动与介质内声波场的分布和起伏相关联，共轭光波形调制现象的强弱取决于介质声子寿命、信号及抽运光强度、有效作用长度等诸多参数.     

Phase Conjugation by Degenerate Four-wave Mixing in Nematic Liquid Crystals

1.IntroductionOpticalphaseconjugationhasbeeninvestigatedextensivelybecauseofitswideapplicationsinimagingtechnology,phase--conjugationlasers,andopticalassociativememorysystems.Notedfortheirlargeopticalreorientationnonlinearities[IJ,nematicliquidcrystals(NLC)havebecomepromisingopticalmediaforapplicationsinthefieldofnonlinearopticsincludingnonlinearphaseconjugation.In1980,Feketectal.[2)firstrealizedphase--conjugationbydegeneratefour--wavemixing(DFWM)inNLCintheisotropicphase.Sincethen,thefie…     

光学相位共轭与四波混频

回顾并论述了光学相位共轭及四波混频技术的发展过程，介绍了四波混频相位共轭的原理、相关的介质材料、应用前景及技术发展趋势。     

Coexistence of Self-pumped Phase Conjugation and Mutual-pumped Phase Conjugation in Ce∶BaTiO3

Self-pumped phase conjugation(SPPC) and mutual-pumped phase conjugation (MPPC) have been found to coexist in Ce∶BaTiO3 by using two coherent beams of 514.5nm wavelength from an argon ion laser. Both phase conjugations are of the stimulated backscattering and four-wave mixing type. For 7/6 incident power ratio and 26 mW total incident power,he shortest phase conjugate mirror formation time is 10s . Phase conjugate reflectivity of one the beams can reach 70%,hich is ～20% higher than the SPPC reflectivity using only one beam. When the total incident power is increased to 40 mW and the incident power ratio remains constant,a maximum phase conjugatate reflectivity of as much as 88% is obtained.     

自泵浦位相共轭反射的实验研究

本文通过检测BaTiO_3晶体的二波耦合增益系数P和自泵浦位相共轭反射率R对随入射角的变化关系,经过理论分析指出R的角度依赖性是P的角密依赖性的结果;详细地解释了全内反射自泵浦位相共轭的双区域耦合理论,指出位相共轭输出的频移特性是泵浦光在双区域间“振荡”的结果;并解释了自泵浦形成的阈值特性。     

Double signal phase conjugation with a Cat conjugator

The phase conjugate reflection of double signals, induced by the self-pumped phase conjugation, is demonstrated in a 16° cut Cu-doped potassium sodium strontium barium niobate (KNSBN) photorefractive crystal. The phase conjugate reflectivities of signals were measured versus the pump-signal beam ratio. A comparison was made between the signal's reflectivity with and without the presence of the other signal beam. The multi-region four-wave mixing model within the same crystal has been employed to explain the geometry performance and the experimental results.     

Directional scattering and self-pumped phase conjugation in photorefractive crystal

The directional scattering in photorefractive SBN crystal is reported.The self-pumped phase conjugation has been realized with the feedback of this directional scattering andthe performance parameters are compared with those of cat self-pumped phase conjugator.     

Ce：KNSBN晶体中产生的双泵浦相位共轭

首次报道在Ｃｅ：ＫＮＳＢＮ晶体中产生的“双”泵浦相位共轭现象，同时还观察到由同一“双”泵浦相位共轭光路所产生的自泵浦相位共轭和四波混频现象。     

KNSBN：Co晶体自泵浦位相共轭特性的研究

本文报道在两块不同尺寸的KNSBN:Co晶体中实现了自泵浦位相共轭输出,通过实验验证了位相共轭反射率与入射角、入射位置以及波长有关,并给出各自的实验曲线.保持激光器工作波长为514.5nm不变,在大块晶体中可得到高达73.0%的位相共轭反射率.文章还给出共轭光的形成时间随系统光强变化关系的实验曲线,并指出自泵浦形成时透射光强和晶体表面反射光强的时间变化特性,解释了自泵浦形成的阈值特性.     

Probe of I(Pj) atoms using two-photon resonant four-wave mixing spectroscopy following the 266-nm photodissociations of various alkyl and perfluoroalkyl iodides

Two-photon resonant four-wave mixing spectroscopy has been utilized successfully for probing I and I^∗ nascent from the 266 nm photodissociations of various alkyl and perfluoroalkyl iodides. The relative quantum yields for I^∗, as well as the recoil anisotropy parameters, were extracted. Recoil anisotropy parameters close to the limit value for parallel transition indicates that the ground-state I(²P_3/2) originates from the curve crossing from the initially prepared ³Q₀ to ¹Q₁ state. The curve-crossing probabilities for alkyl and perfluoroalkyl iodides were obtained and tried to explain using the well-known Landau-Zener model. In the cases of perfluoroalkyl iodides, it is necessary to consider the fluorination effect to describe the detailed dynamics observed in this study and has been revealed that the electronic effect due to fluorine atom substitution is dominant, leading to decrease in the curve-crossing probability.     

Phase coding in iterative synthesis of computer-generated holograms

A new method is investigated for phase-only hologram synthesis. The method combines iterative calculation of the hologram phase function with the coding of the amplitude-phase characteristics of the complex transmission function into phase characteristics. The results of computational experiments are presented. The phase masks and reconstructed object images are also presented.     

甲基橙掺杂聚乙烯醇薄膜简并四波混频特性的实验教学研究

介绍了在近代物理实验课中开设甲基橙掺杂聚乙烯醇薄膜的简并四波混频特性的实验设计，论述了实验原理和实验中采用的非线性介质的结构与性能．研究了泵浦光与探测光之间的夹角等实验条件对实验结果的影响，得到了相位共轭光强度与探测光和泵浦光的关系．分析了实验中产生的信号光强度和反射系数的变化及产生这种变化的机制．