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题名	双掺杂LINbO_3非挥发全息记录／固定最佳化的理论和实验研究
作者	任立勇
学位类别	博士
答辩日期	2004
授予单位	中国科学院上海光学精密机械研究所
导师	刘立人
关键词	光折变效应 双掺杂妮酸鲤 非挥发全 岔记录 光固定
其他题名	Theoretical and Experimental Study of the Optimization of Nonvolatile Holographic Recording/Fixing in Doubly Doped LiNbO_3 Crystals
中文摘要	Buse等人提出的双掺杂LINbO_3：Fe:Mn晶体采用双色光实现非挥发全息数据存储[Nature，393，665（1998）]不但是一利非常实用化的全光学全息、固定技术，而且在多功能三维光学集成方面有潜在的应用前景。但该方案仍存在衍射效率低、光散射噪声强不响应速度慢等影响其实际应用的问题。理论上和实验上深入研究该方法的微观机制，对于光折变全息的优化、局域光学功能元件的集成、双掺杂材料的发展、及该技术实用化的推进具有深远的意义。本论文论述了作者在双掺杂LINbO_31晶体非挥发全息、记录的理论和实验方而的一些工作，主要包括：（1）望也于光对物质的作用和物质对光的作用是光折变效应的两个不可分判的过程这一雄木思想，通过联立两中心带输运物质力一程和双光束拙合波方程，建立了双掺杂LINbO_3晶体光折变特性的时空动态理论。得到了一组描述光折变时空动力学的微分方程组，数值求解并给出了LiNbO_3:Fe:Mn晶体光折变的时空演化细节。详细讨论了非挥发全息的优化条件。绝大多数结论与先前的理论和实验结果一致。研究表明：由于双光束机合效应，钻体内形成了非均匀的折射率光通册，并且等相位线也相应地出现了弯曲；当空间「助柳勿与光波干涉场之间的相对相移反号时，光能量拙合方向也才目应地发生反转；还原屏：体的全息读出过程总是伴随着快速的相位变化，最终实现了电子的均匀分布，从而导致了所记录的光信息逐渐被擦除。当形成的折射率光栅较强时，双光束祸合效应会加剧，一记录过程中衍射效率会随时间振荡。(2)发现了弱氧化LINbO_3:Ce:Cu晶体全息记录过程中衍射效率的振荡现象，并将该特性用于提高固定衍射效率。实验表明，在衍射效率达到第一个最大之后，存在一个全息从记录到固定的最佳切换，可以获得很高的固定衍射效率，实验上测得衍射效率高达70％。数值模拟表明，在最佳切换处的理论上衍射效率可高达100％。上述方法提供了一个获得高的固定衍射效率的崭新思路。研究了最佳切换与况．体厚度的关系。发现为了利用最佳切换，晶体应进行适当的弱氧化。在LINbO_3:Ce:Cu晶体中首次观察到了全息记录与读出过程中的自增强效应，采用动态理论给出了数值模拟，理论与实验结果是一致的。(3)研究了杂质粒子的微观光学参量对非挥发全息记录的影响。运用电荷交换模型从理论上解释了双掺杂晶体的光色效应、漂白效应和不敏感效应。计算并讨论了深、浅掺杂中心的微观光学参量和相应的光色／漂白因子对"记录饱和与固定的空间电荷场的影响。研究表明，光色效应越强，，记录饱禾｝空间电荷场越大，记录灵敏度越高；对于给定的光色／漂白因子，氧化性越强记录饱和空间电荷场越小，但固定的空间电荷场却变大；晶体的光学质量是决定信噪比的关键因素；为了得到高的信噪比，应该选择电子复合系数较大的深掺杂中心和电子复合系数较小的浅掺杂中心，但这又将以降低一记录饱和与固定的空间电荷场为代价，所以实际上需折衷考虑
英文摘要	Nonvolatile holographic data storage in lithium niobate crystals doubly doped with Fe:Mn by using the two-color beams proposed by Buse et al. [Nature, Vol. 393, pp.665 (1998)] is not only a very applied and all-optical holographic fixing technique, but also has the important potentials in the multifunctional integrated 3-D optical system. However, in practical applications, this scheme still has some important problems, such as low diffraction efficiency, strong optical scattering noise and slow response velocity, and so on. The in-depth theoretical and experimental studies of the microscopic mechanism of this method have far-reaching significance which includes the optimization of photorefractive holographic, the integration of local optical functional component, the exploration of other doubly doped materials, and the advance of its practicability. In this dissertation, theoretical and experimental studies of nonvolatile holographic recording in doubly doped LiNbO3 crystals are presented: (1) Based on the essential idea that the material response to the light and the light response to the material are the two indiscerptible processes of photorefractive effect, we set up the time-space dynamic theory of the nonvolatile holographic recording in doubly doped LiNbO_3 crystals by jointly solving the two-center material equations and the coupled-wave equations. The time-space evolution of the photorefractive parameters of LiNbO_3:Fe:Mn crystal is given by numerically solving a set of differential equations. The optimal conditions for material prescriptions and oxidation-reduction processing are discussed in detail. Most of our results are consistent with the formers' theoretical and experimental ones. We found that, the nonuniform photorefractive grating and the bending isophase of the fringe pattern are produced inside the crystal; the energy transferring direction between the two-coupled beams can be reversed with the reversal of the sign of the relative phase shift between the space-charge field and the intensity pattern; the holographic readout in reduced crystal is always accompanied by the fast phase changes, which results in the slow deterioration of the recorded holograms by producing homogeneous electron distribution; for the relative strong index-grating the diffraction efficiency may oscillate during the recording step. (2) An oscillatory characteristic of diffraction is observed in a weakly oxidized LiNbO_3:Ce:Cu crystal during the holographic recording. Experiment indicates that, after the first diffraction maximum, there exists an optimal switching time from the recording step to the fixing step which can produce a high diffraction of fixed hologram. High diffraction efficiency of 70% is observed in LiNbO_3Ce:Cu crystal. Numerical simulation shows that the optimal switching will lead theoretically the fixed diffraction up to 100% with a suitable switching time. This method provides us a new idea to obtain high persistent diffraction efficiency. The relationship between the optimal switching and the crystal thickness is studied. The self-enhancement effect of LiNbO_3:Ce:Cu crystal is observed in both the stages of holographic recording and readout. Using the dynamic theory the numeric simulations are given which can well confirm the self-enhancement experiments. (3) Using the charge exchange model the photochromic effect, bleaching effect and the no-sensitization effect of doubly doped LiNbO_3 crystals are interpreted theoretically. The effect of the microscopic optical parameters of the deep and shallow doping centers as well as the corresponding photochromism-bleach factor on the saturation and fixed space-charge field is calculated and discussed. It shows that, the stronger the photochromic effect, the larger the saturation space-charge field and the higher the recording sensitivity; for a given photochromism-bleach factor, stronger oxidization will lead to smaller saturation space-charge field but relative larger fixed one; the optical quality of crystal is the key factor to influence the signal-to-noise ratio; in order to obtain high signal-to-noise ratio, we should select the deep center with large electron recombination coefficient and the shallow center with small one, but this selection will be at the expense of the decreasing of the saturation and fixed space-charge fields, so in practice a trade-off is always needed.
语种	中文
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/15445]
专题	上海光学精密机械研究所_学位论文
推荐引用方式 GB/T 7714	任立勇. 双掺杂LINbO_3非挥发全息记录／固定最佳化的理论和实验研究[D]. 中国科学院上海光学精密机械研究所. 2004.

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