铈铁掺杂铌酸锂晶体光折变性能的研究

对铈铁掺杂铌酸锂(Ce:Fe:LiNbO3)晶体进行氧化、还原处理。通过红外光谱、紫外可见吸收光谱测试了晶体样品的组成和缺陷结构。采用透射光斑畸变法测试了晶体样品的抗光损伤能力,结果表明:生长态晶体比还原态晶体的抗光致散射能力基本上高一个数量级,氧化态的晶体要比还原态的晶体高两个数量级。采用二波耦合实验测试了晶体样品的光折变性能,结果表明:从氧化到生长再到还原态,衍射效率逐渐降低,响应时间缩短,光折变灵敏度增加,动态范围逐渐降低。     

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     

光学自增强效应与衍射效率的提高

利用含时光折变双光耦合方程数字模拟计算了掺铁铌酸锂晶体中双光耦合的动态过程,分析了空间电荷场及其位相、光折变光栅位相等光折变参量的变化过程,解释了光折变自增强效应,提出了提高光折变光栅衍射效率的有效方法．     

四价掺杂铌酸锂晶体

综述了四价掺杂(包括铪和锆)铌酸锂晶体的研究进展.掺铪铌酸锂晶体具有与掺镁铌酸锂晶体相似的抗光折变性能,而掺锆铌酸锂晶体的抗光折变性能远优于掺镁铌酸锂晶体.铪铁双掺与锆铁双掺铌酸锂晶体兼有高光折变灵敏度和高光折变衍射效率的性质.并且在掺杂量超过阈值时,铪离子和锆离子在铌酸锂晶体中都具有接近于1的有效分凝系数.这些实验结果表明,四价掺杂铌酸锂有望成为出色的非线性光学晶体.     

同成份掺杂铌酸锂晶体中紫外-红光非挥发全息存储的研究

我们研究了单掺镁、锌、铟的同成份铌酸锂晶体的紫外-红光双色非挥发全息存储性质。通过对不同掺杂浓度铌酸锂晶体的紫外-红光双色全息存储衍射效率、灵敏度、响应时间、动态范围等参数的测量，我们发现掺杂浓度超过抗光损伤阈值的同成份铌酸锂晶体在引入紫外光辐照后，响应时间明显缩短，双色记录灵敏度显著增加，而且存储机制不同于低于阈值浓度的晶体，均可以实现非挥发全息存储；并且，对于不同的掺杂离子，光折变光栅的形成机制也有所不同。     

光折变晶体全息存储中散射噪声特性的研究

采用信噪比损失系数 (LSNR)深入研究了光折变铌酸锂晶体中散射噪声对全息输入图像像质的影响。对不同掺杂物质、不同掺杂浓度、不同处理方法以及不同记录方式的大量晶体进行了实验研究 ,并重点考察了物光束引起的散射噪声的特性。实验结果表明 ,氧化态晶体的散射噪声的影响小于生长态和还原态晶体 ,反射光路较之透射光路和邻面入射 ( 90°)光路更不易受散射噪音影响     

双掺钾钠铌酸锶钡晶体光学特性研究

成功地生长、制备出了双掺（Cu,Ce)钾钠铌酸锶钡晶体样品,测量了双掺（Cu,Ce)钾钠铌酸锶钡晶体在红光波段的二波耦合特性及其光诱导吸收变化。实验结果显示,双掺（Cu,Ce)钾钠铌酸锶钡晶体在红光波段具有好的光折变性能,基红光波段的二波耦合增益可达10cm^-1;且存在着较强的光诱导吸收现象,其光诱导吸收变化明显地依赖于泵浦束光强和探测束光偏振,探测束偏振方向平等晶体c轴时的光诱导吸收系数和探测束偏振方向垂直于晶体c轴时的光诱导吸收系数分别达0．53c^-1和0．26cm^-1,并以实验结果用两光折变中心模型进行了解释。     

Ce：KNSBN晶体红光两波耦合特性研究

用红光对掺铈的铌酸钾钠锶钡(KNSBN)单晶样品进行了两波耦合的测量,研究了两波耦合中样品的增益系数Γ与两束入射光夹角2θ的关系.用光折变理论拟合了Γ-2θ关系的实验结果,求出了该样品的有效光折变电荷密度,有效电光系数和电子-空穴对抗率的数值.     

Ce∶KNSBN晶体红光两波耦合特性研究

用红光对掺铈的铌酸钾钠锶钡（ＫＮＳＢＮ）单晶样品进行了两波耦合的测量，研究了两波耦合中样品的增益系数Γ与两束入射光夹角２θ的关系。用光折变理论拟合了Γ２θ关系的实验结果，求出了该样品的有效光折变电荷密度，有效电光系数和电子空穴对抗率的数值。     

激光驾束制导偏振编码器设计参数

针对偏振编码激光驾束制导对编码器的要求,基于铌酸锂晶体的电光效应,设计了适用的编码器.编码器采用铌酸锂双晶体块空气层耦合,可以把线偏振光转换成与空间位置对应的多偏振态输出.对编码器设计中能量透过率、空气层厚度、调制电压等问题进行了分析,分析结果表明,空气层产生的光程差和空气层厚度成正比,和编码器的长高比成反比,半波电压与编码器的长高比成正比,采用铌酸锂双晶体耦合偏振编码器,编码器的长高比应大于2.7.实验结果表明:编码器可以实现空间偏振编码.     

Polarization properties of enhanced self-diffraction in sillenite crystals

Doppler-enhanced self-diffraction in two-beam coupling experiments with sillenite crystals exhibits pronounced optical polarization effects due to the concomitant presence of natural optical activity and electric-field-induced linear birefringence. Coupled wave equations that describe the polarization properties, exclusive of self-diffraction effects, have previously been derived for the two principal crystal orientations most commonly used in photorefractive recording. In this paper, the coupled wave equations are combined with a linearized model of the photorefractive recording process (single trap level, single mobile charge species) to analyze the impact of self-diffraction effects on the polarization state evolution. Numerical solutions of these equations yield optimum configurations for enhanced gain and improved image contrast in two-wave mixing with such materials. In addition, inclusion of optical activity in the model emphasizes the contribution of this effect to the apparent reduction of the effective electrooptic coefficient of bismuth silicon oxide crystals.     

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。     

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°     

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。     

BaTiO_3晶体光折变效应振荡器和机理研究

在薄征Ce:BaTiO3晶体和体块Rh:BaTiO3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建立了光折变效应准线笥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BaTiO3晶体的受激光折变散射自泵浦相位共轭的影响。     

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     

A Vernier S-shaped fiber double-loop resonator with double couplersand degenerate two-wave mixing

The use of degenerate two-mixing in a S-shaped fiber double-loop resonator with double couplers to achieve the Vernier operation is proposed. The degenerate two-wave mixing is implemented by inserting a short strand of a photorefractive fiber into the common segment of two fiber loops. With a suitable two-wave mixing gain and a suitable ratio between the free spectral ranges of the two fiber loop resonators, the effective free spectral range can be increased significantly