BaTiO_3晶体光折变效应振荡器和机理研究

在薄片 Ce:Ba Ti O3晶体和体块 Rh:Ba Ti O3晶体实现了光折变效应振荡器。利用前向二波耦合和相向二波耦合理论建立了光折变效应准线性 F- P腔模型 ,并从实验结果上进行了验证和分析 ,同时分析了光振荡现象对 Ba Ti O3晶体的受激光折变散射自泵浦相位共轭的影响     

BaTiO3相干光CW图象放大器

首次使用国产光折变晶体BaTiO3利用两波耦合效应，成功地攻得相干光CW图象（强度）放大。文中具体给出了放大率与泵浦功率，泵光与信号光比率，泵光与信号光相对晶体晶轴取回的依赖关系。     

Ce:Mn:LiNbO_3晶体光折变效应及应用

铌酸锂晶体非线性光学系数大,易于掺杂并能保证较高的光学质量,所以仍然是目前应用较广的光折变材料之一。本文报道铈锰双掺铌酸锂(Ce:Mn:LiNbo_3)的晶体的光折变效应及其在二波耦合和实时全息关联存储中的应用,并对实验结果进行了讨论和     

双掺杂LiNbO3晶体光折变效应研究

研究了系列不同掺杂、不同掺杂浓度、单掺杂和双掺杂以及不同后处理态(生长态、还原态和氧化态)铌酸锂晶体的透过率光谱和光折变二波耦合效应。实验结果表明，高掺杂铌酸锂样品的透过率光谱范围较窄；双掺杂样品比单掺铁样品的抗光折变效应增强，光折变效应降低。氧化态样品具有较大的透过率光谱范围；还原态样品具有较大的光折变二波耦合增益特性。     

光折变Bi12TiO20晶体中的波耦合性质

研究了光折变Bi12TiO20(TBO)晶体中的二波耦合矢量特性.对扩散记录全息求得信号光能量增益和偏振态改变的分析解,研究它们在3种制备可得的晶体切割面上随入射抽运光和信号光(不同)偏振方向、光栅取向以及晶体厚度的变化关系,并给出在任意光栅取向的取值范围.分析了信号光能量增益和偏振态改变量分别达到最大值时各向同性和各向异性耦合的作用,并研究旋光、压电及弹光效应在3种晶体切割面上对矢量波耦合的影响.     

双光子光折变晶体中全息屏蔽空间孤子

为了得到双光子光折变晶体中全息屏蔽空间孤子的结果,基于双光束耦合耗散系统和双光子光折变效应,证明了外加偏压的双光子光折变晶体中存在一种新的全息屏蔽空间孤子。此类孤子需要满足两种平衡,一是损耗与增益之间的平衡,增益由抽运光通过两波耦合为信号光提供;二是衍射与非线性之间的平衡,非线性包括外加电场的非均匀屏蔽和两波耦合对折射率的周期性调制。在信号光远小于抽运光的条件下得出了全息亮和暗孤子的解析表达式。研究了全息屏蔽孤子的演化特性。     

光折变的光学脉动现象及其非线性过程

报道了光折变LiNbO_3:Fe晶体中双光束耦合和四波混频的脉动现象。认为这种脉动现象起因于LiNbO_3:Fe晶体中的陷阱重复荷电波在光折变材料中感应出的运动折射率光栅。     

背向受激二波混频产生自泵浦相位共轭

本文讨论了在光折变晶体中,通过特殊的背向受激二波混频产生自泵浦相位共轭波的理论,并指出散射波的频偏是由于极化光折变晶体中的光生伏打效应引起相位栅的运动而产生的。     

BaTiO_3相干光CW图象放大器

首次使用国产光折变晶体BaTiO_3利用两波耦合效应,成功地获得相干光CW图象(强度)放大。文中具体给出了放大率与泵浦功率,泵光与信号光比率,泵光与信号光相对晶体晶轴取回的依赖关系。     

掺铑钛酸钡晶体中温度增强的光折变性质

掺铑钛酸钡晶体是一种近年来生长成功的光折变晶体。人们对它的光折变性质如二波耦合、相位共轭、光致吸收等都做过很多研究。但关于其光折变性质随温度的变化尚未见报导。本文中我们对物理所生长的掺铑钛酸钡晶体的光折变性质对温度的依赖性进行了研究，发现其二波耦会强度及其相位共轭反射率随温度的升高而增加。在二波耦合实验中，我们用He－Ne激光器作光源，为消除强的扇光而采用o光偏振，两束对称入射（晶体外夹角2θ=18°）。泵浦光强度为0．36W／cm2，泵浦光与信号光的强度比为为20，测得二波耦合强度随温度线性增加，当温度从20℃…     

非相干光对Ce:KNSBN晶体两波耦合的影响研究

理论分析和实验研究了非相干光照射下Ce:KNSBN晶体中的两波耦合,发现非相干光在很大范围内可有效地控制晶体中的两波耦合效应。实验结果和理论分析趋势相一致。     

Gain constant of two-wave mixing in periodically poledphotorefractive crystal waveguide

A photorefractive crystal waveguide with its c-axis periodically reversed along the waveguide axis is studied to realize enhanced two-wave mixing. The gain constant of two-wave mixing in the periodically poled photorefractive waveguide is theoretically derived in terms of mode-coupling analysis. It is found that, in BaTiO₃ periodically poled waveguides, the net two-wave mixing gain constant is increased by 1.5 to 5 times over that of conventional waveguides without periodical poling because the largest electrooptic coefficient r₄₂ can be effectively used by appropriately setting the angle between the c- and z-axes. Several types of test BaTiO₃ periodically poled waveguides are successfully fabricated by using the electrical poling technique. Typical lateral dimensions of the waveguides are O.5 to 1 mm, and the lengths are several millimetres. The measured two-wave mixing gain constants of the fabricated waveguides are well predicted by the theory     

Photorefractive phase conjugators

The author presents a tutorial review of various kinds of optical phase conjugators using photorefractive materials. These include externally pumped phase conjugators (EPPCs), self-pumped phase conjugators (SPPCs), and mutually pumped phase conjugators (MPPCs). He briefly describes optical phase conjugation and the photorefractive effect. He also describes wave mixing in photorefractive media. The energy transfer in two-wave mixing and the holographic nature of four-wave mixing are discussed     

Intensity Dependence of Stationary Energy Transfer in Codirectional Photorefractive Two－wave Mixing

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Intensity Dependence of Stationary Energy Transfer in Codirectional Photorefractive Two—wave Mixing

The intensity and phase formulas that are valid for the saturation and inter-mediate regime(before saturation)are derived,and the analytical expressions with the ration of saturation intensity to total incident intensity as their explicit variable are obtanied.The intensity depenence of stationary energy transfer in photorefractive acodirectional two-wave mixing is examined.It is necessary to using these formulas in some problems,such as the temperature of intensity dependence of two-wave mixing.A method of measuring exponen-tial gain coefficient is presented,which is suitable for two-wave mixing in intermediate regime.     

光折变效应和两波混频

近10年来光折变光学取得了显著的进展,它已成为非线性光学领域的重要课题。本文首先扼要地介绍光折变效应及其产生的物理机制和几种基本的光折变现象,然后较详细地叙述两波混频过程。     

Optical beam equalisation using degenerate two-wave mixing

Optical beam equalisation using degenerate two-wave mixing with photorefractive crystals is proposed. The relationship between parameters to achieve beam equalisation is derived.     

Theory of amplitude and phase effects in 2-D-two-wave mixing

The two-wave mixing process in a photorefractive medium is investigated including nonuniform amplitude distributions of the pump and signal waves, plane-aberrated phase fronts, absorption, and arbitrary grating phase shift φ. The resulting system of two-dimensional coupled-wave equations is solved numerically with the aid of a two-dimensional Runge-Kutta method. Numerical data are shown to explain the gain distributions and image distortion properties in photorefractive amplifiers of the crossed beam, transmission and reflection grating type. A simple relation is presented describing the amplitude-phase crosstalk in two-wave mixing. One example is illustrated showing the possibility for compensating for aberrations using special pump and/or signal beam profiles with a grating phase shift different from 90°