有机-无机纳米复合光折变材料的研究与进展

在聚合物中掺杂无机半导体纳米粒子作为光敏剂制备的有机-无机纳米复合光折变材料是一种新型的光折变材料.详细介绍了有机-无机纳米复合光折变材料的制备方法、光折变性能及其存在的问题,展望了这类新型材料的潜在优势和发展前景.     

锗酸铋晶体光电导性质的研究

生长了六种掺杂锗酸铋(简称 BGO)晶体(分别掺 Fe、Cr、Mn、W、Pb 和 Ce)。在合适的测试条件下,测量了它们的光吸收系数、光电导参数和暗电导率,并与未掺杂样品进行了比较。计算出了样品的特征参量μφτ,为上述材料光折变性质的研究提供了必不可少的数据。在此基础上,对 BG0∶Cr、BGO∶Fe 和BGO∶Mn 晶体的光折变机制进行了简略的讨论,认为 BGO∶Cr 中的光折变中心可能是:Cr~(3+)作为施主,Cr~(4+)作为电子陷阱;或 Cr~(4+)作为受主,Cr~(3+)为空穴陷阱。     

Cr:KNSBN光折变晶体非简并四波混频特性

应用波长为514.5nm的Ar^＋离子激光和波长为632.8nm的He-Ne激光对Cr：KNSBN光折变晶体的非简并四波混频特性进行了实验研究．测量了相位共轭光的时间变化过程，相位共轭反射率随信号光与前向泵浦光夹角的关系，相位共轭反射率与泵一泵比的关系及相位共轭反射率与信，泵比的关系．实验发现，当信号光与前向泵浦光的夹角为21^。泵-泵比为0.36时可获得最大的相位共轭反射率30％．利用相应的光折变理论对相位共轭反射率与泵-泵比、相位共轭反射率与信．泵比的关系进行了数值拟合，数值计算结果与实验测量结果有较好的吻合．该项研究为Cr：KNSBN晶体在图像变换、彩色相位共轭和波前整形等领域的应用提供了实验依据．     

四硼酸锂单晶的光学性能表征

本工作测试了ＬＢＯ单晶的折射率、电光系数、光吸收谱、红外光谱和喇曼光谱，详细分析了ＬＢＯ晶体的光谱及其相应的晶格振动情况。实验表明，透明的、未掺杂的ＬＢＯ晶体没有观察到明显的光折变效应。     

光折变聚合物材料的研究进展

与无机光折变晶体相比,光折变聚合物材料具有非线性光学系数大,响应时间快,成本低廉,制备灵活等优点,成为近代研究的热点。综述了光折变聚合物材料的发展状况,并分析了当前工作所面临的问题及发展前景。     

新型三维存储材料及应用

通过实施双掺杂工程,既控制光折变晶体中的光折变敏感中心(即施主中心),又控制其中的电子陷阱中心,优化双掺LN晶体的光折变存储特性,得到了优良的光存储材料,同时,利用光折变全息记录以及全光固定光栅技术,研制成三维全息存储器原型。具体研究成果如下: (1)首次在国际上发现光强阈值效应,打破了国际上传统的“与光强无关”的概念,同时,首次提出最佳写入光强的概念;首次发现高掺镁晶体的紫外光折变增强效应,打破了国际上的“掺镁抗光折变”的概念的绝对化;建立了国际上较为完善的晶体缺     

光折变聚合物的研究进展

近年来，聚合物光折变材料越来越受到人在关注，因为民无机材料相比，聚合物材料有较高的电光系数，较高的光损伤阈值，低的直流电常数，而且易于加工，所以光折变聚合物材料显示光明的应用前景，文中介绍了光折变产生的简单的机理，以及目前国际上所研究的各类材料及发展状况。     

Ti:Fe:LiNbO_3晶体的生长及其光折变性能的研究

采用熔体提拉法生长了不同掺杂浓度的Ti：Fe：LiNbO3晶体．研究了掺杂杂质离子浓度变化对晶体光折变性能的影响，测定了晶体经热化学还原处理前后的透射谱．用ESR方法证实，未经还原处理时，Ti：Fe：LiNbO3晶体中Ti离子以Ti4 形式存在．与Fe：LiNbO3和Ti：LiNbOa相比，Ti、Fe复合掺杂，通过电荷补偿效应，使未经还原处理的晶体中Fe2 增加，从而使光吸收增强；可以通过改变Ti、Fe掺杂浓度的方法来控制晶体中Fe2 离子的浓度，达到控制并改善晶体光折变性能的目的．本文还对Ti：Fe：LiNbO3晶体的全息性能进行了研究，测得Ti：Fe：LiNbO3晶体响应时间缩短，衍射效率高达90％以上．Ti：Fe：LiNbO3晶体是一种优质的光折变材料．     

Fe：Mn：LiNbO3晶体的生长及光学性能研究

采用坩埚下降法生长了掺杂Fe^3＋和Mn^2＋的LiNbO3单晶。晶体经极化处理后,用X-射线衍射仪测试了晶体的晶格常数,讨论了掺杂离子对晶格常数的影响。利用二渡耦合实验测试了晶体的指数增益系数、衍射效率和响应时间,结果表明：Fe：Mn：LiNbO3晶体的最大指数增益系数达到40cm^-1,Fe：Mn：LiNbO3的最大衍射效率分别为76％,二波耦合响应时间为2．5min。Fe：Mn：LiNbO3是一种性能优良的光折变晶体。     

KTN∶Cu晶体的铁电和光折变性能

用熔盐提拉法培育了掺 Cu~(2+)离子的 KTa_(1-x)Nb_xO_3(KTN∶Cu,x=0.32)晶体;在±160℃范围内测量了介电常数、介质损耗、自发极化强度和热释电系数;用 Ar 激光和二波混频法测量了室温下的光折变性能;扼要讨论了它的铁电相变特点和光折变性质.结果表明,该晶体的两个铁电-铁电相变为一级相变,而它的铁电相变已开始趋向于二级相变;室温立方相的衍射效率已高达52%,光折变灵敏度为3.2×10~(-6)cm~3/J,光折变动态范围Δn 为2.33×10~(-5),表现出良好的光折变应用前景.     

Diffraction properties of transmission photorefractive volume gratings in a cerium-doped potassium sodium strontium barium niobate crystal

The diffraction efficiency of volume gratings written by two-wave mixing in a cerium-doped potassium sodium strontium barium niobate (Ce:KNSBN) photorefractive crystal is studied. It is found that the diffraction efficiency strongly depends on the polarization of writing beams and exhibits loop behavior with respect to the fringe modulation. The fringe modulations before and behind the crystal are compared. Modified coupled-wave theory is used to fit the experimental data. This research presents data that are relevant to the application of Ce:KNSBN crystals to holographic recording and optical information processing.     

Photorefractive Polymers and Composites

Materials demonstrating a photorefractive effect are principal candidates for numerous applications, including high-density optical data storage, optical image processing, phase conjugated mirrors and lasers, dynamic holography, optical computing, pattern recognition, etc. Considerable progress has been made in the research on photorefractive polymers and composite materials in the last few years. These materials have many advantages over inorganic photorefractive crystals, including large optical nonlinearities, low dielectric constants, low cost and ease of fabrication. A large number of materials, including those exhibiting an extremely large photorefractive effect, have been developed. In addition, a number of interesting phenomena particular to polymeric photorefractive materials have been reported and corresponding mechanisms have been proposed to account for these phenomena. Possible applications of these materials have been explored with the demonstration of a volume holographic storage device based on photorefractive polymers. This paper reviews the latest developments of the young and exciting field of polymeric photorefractive materials.     

光折变材料研究进展

光折变材料研究是当今非线性光学学科的一个重要领域和研究热点，概述了光折变材料的特性及其应用；比较，综述了无机晶体，聚合物和无机-有机复合等三类光折变材料的性能，研究进展以及面临的主要问题和发展趋向；评述和展望了近年来出现的无机-有机复合光折变材料的研究意义。潜在优势和发展前景。     

KNSBN:V晶体材料制备及光诱导吸收研究

成功地生长、制备出了一系列含不同掺钒浓度的钾钠铌酸锶钡（ＫＮＳＢＮ：Ｖ）晶体样品。测量了在不同光强、光偏振和掺钒浓度下ＫＮＳＢＮ晶体的光诱导吸收变化。实验结果显示,ＫＮＳＢＮ：Ｖ晶体存在较强的光诱导吸收,且其光诱导吸收变化明显依赖于泵浦束光强,探测束光偏振和晶体的掺钒量,对于探测束光偏振平行和垂直于ｃ轴的情况其值分别可达０．５５和０．２２ｃｍ＾－１。对实验结果进行了解释。     

Tracking novelty filter at 780 nm based on a photorefractive polymer in a two-beam coupling geometry

We have constructed an all-optical tracking novelty filter based on the dynamic holographic properties of an efficient and fast infrared-sensitive photorefractive polymer. The photorefractive polymer was used in a two-beam coupling geometry. The polymer had a gain coefficient of 175 cm(-1) at a wavelength of 780 nm and an applied field of 72 V/mum. In contrast to what has been observed in photorefractive crystals, the gain coefficient and the filter contrast are largely independent of the writing beam's intensity ratio. We show images of a swinging pendulum observed through the novelty filter.     

The threshold effect of incident exposure energy flux for photorefractive light-induced scattering in doped lithium niobate crystals

The threshold effect of incident exposure energy flux is proposed to measure the light-induced scattering in doped LiNbO₃ crystals. The dependences of the exposure energy flux threshold on the concentration of damage-resistant dopants as well as oxidation–reduction treatment are investigated experimentally in doped LiNbO₃ crystals. The results show that doping with damage-resistant dopants and oxidation–reduction treatment are simple and effective methods to control and optimize the photorefractive properties of doped LiNbO₃ crystals. The high signal-to-noise ratio reconstructions are also demonstrated experimentally according to the incident exposure energy flux threshold in triply-doped LiNbO₃ crystals. Comparing with the known incident intensity threshold method, the exposure energy flux threshold method is more effective for estimating the light-induced scattering of photorefractive recording materials.     

Holographic recording with orthogonally polarized beams in a cesium-doped (K0.5Na0.5)0.2(Sr0.75Ba0.25)0.9Nb2O6 crystal

Holographic recording with orthogonally polarized beams in a cesium-doped KNSBN [(K(0.5)Na(0.5))(0.2)(Sr(0.75)Ba(0.25))(0.9)Nb(2)O(6)] crystal has been studied. It was found that this kind of photorefractive crystal possesses high linear dichroism, which makes it suitable for use in polarization holography. The diffraction efficiency as a function of the polarization orientation of the reference beam and as a function of the fringe modulation at the optimum polarization orientation of the reference beam is experimentally investigated. Theoretical fitting based on Kahmann models was performed and agrees well with the experimental data. In the experiments, both polarization holography and conventional holography are used to record a binary object. The reconstruction shows that polarization holography with Ce:KNSBN is highly effective, exhibiting high diffraction efficiency and reduced fanning noise.     

具有宽度的线状物体的边缘增强

介绍一种对具有宽度的线状物体实现边缘增强从而达到识别目的的方法。利用置于相干系统傅里叶平面的光折变晶体ＣＵ：ＫＮＳＢＮ在一定条件下产生位相复共轭效应，从面形成拉普拉斯算子，最后在象平面输出线状物体的边缘增强象。文中给出实验结果及扼要的理论分析。     

双掺杂LiNbO3晶体的生长及其实时图象微分的研究

采用Ｃｚｏｃｈｒａｌｓｋｉ Ｚｎ：Ｆｅ：ＬｎＮｂＯ３晶体和Ｃｅ：Ｎｄ：ＬｉＮｂＯ３晶体。测试了晶体的抗光致散射能力、衍射效率和响应时间。以双掺杂ＬｉＮｂＯ３晶体作为全息记录材料,Ｃｅ：Ｃｕ：ＫＮＳＢＮ晶体构成自泵浦位相共轭镜,进行了实时图象边缘增强的研究,并探讨了不同的记录晶体对实验结果的影响。