双掺杂LiNbO3晶体近红外非挥发全息记录与优化
文献类型：学位论文
| 作者 | 李大汕 |
| 学位类别 | 博士 |
| 答辩日期 | 2007 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 李大汕 |
| 关键词 | 光折变效应 双掺杂铌酸锂晶体 非挥发全息记录 近红外全息记录 激光诱导畴反转 |
| 其他题名 | Experimental Study and Optimization of Near-infrared Nonvolatile Holographic Recording in Doubly Doped LiNbO3 Crystals |
| 中文摘要 | Buse等人提出的双中心全息记录法，在双掺杂LiNbO3晶体内采用两种不同波长的光实现了非挥发全息记录，并且具有全光性、实时实地性等优点，因而成为一种广受关注的全光学全息固定技术。LiNbO3:Ce:Cu晶体是一种性能优良、具有良好应用前景的双中心全息记录材料，有必要对其进行深入的理论研究，优化记录性能；同时目前双中心记录以短波长可见光为记录光，将其扩展到近红外波段，对于拓宽双中心全息记录应用领域具有重要意义。本论文论述了作者在以上两个方面所开展的理论与实验研究工作，主要内容包括： (1) 采用基于PDECOL算法的数值方法严格求解光折变带输运偏微分方程组。利用此方法，得到了任意调制度下空间电荷场分布的时空变化及其稳态解，并与耦合波方程联立求解，模拟了大调制度与强外加电场条件下光折变晶体中动态两波耦合的过程。发现此时线性近似理论理论已不再适用，晶体中两波耦合增益大大增强，两束记录光之间发生能量和相位转移，记录干涉光条纹的相位随晶体厚度变化，记录的光栅条纹不再均匀，发生扭曲。 (2) 首次利用LiNbO3:Fe:X双掺杂晶体实现了近红外非挥发全息记录。通过研究发现LiNbO3:Fe:Ni与LiNbO3:Fe:Rh在752.5nm、799.3nm近红外光记录波长下具有最佳的双中心非挥发全息记录性能。在研究浅中心Fe在近红外全息记录中的作用时，发现由于掺杂在LiNbO3晶体中Fe杂质在1.6eV(760nm)左右具有吸收谷值，LiNbO3:Fe、LiNbO3:Fe:Ni和LiNbO3:Fe:Rh三种晶体在752.5nm记录时达到了很高的饱和折射率变化。实验中发现LiNbO3:Fe:Ni和LiNbO3:Fe:Rh两种晶体在以752.5nm与799.3nm作为记录光时，光强特性与633nm红光为记录光的双中心全息记录不同，从Fe杂质在近红外波长光生伏特系数下降、响应时间延长以及敏化光在记录时的光栅擦除效应等角度给予了解释。 (3) 详细研究了LiNbO3:Ce:Cu晶体双中心全息记录的特点及其产生原因。由文献推导了晶体的微观参量，利用数值方法严格求解双中心带输运方程组，研究了记录与敏化光强、深浅中心杂质掺杂浓度以及晶体微观参量对记录的影响，并进行了实验验证。通过与LiNbO3:Fe:Mn晶体的双中心记录模拟结果相比较，发现LiNbO3:Ce:Cu晶体实现高衍射效率与固定效率的主导因素是深中心Cu建立了很强的空间电荷场。 (4) 研究了647nm红光诱导LiNbO3:Mg晶体畴反转的效应，发现了晶体成核场降低效应。研究了诱导光强对成核场电压降低的影响，发现激光从晶体的不同表面入射时对成核场电压的降低有不同的作用，这是以前研究激光诱导过程中所没有发现的。从实验现象出发，给出了激光诱导畴反转效应产生的解释。 |
| 英文摘要 | Nonvolatile holographic recording in doubly doped LiNbO3 crystals by using the two-color beams proposed by Buse et al. has received a great deal of attention, because of its inherent merits of all-optical and real time holographic fixing. LiNbO3:Ce:Cu crystal is one of the most promising materials for two-center holographic recording, so further theoretical study is needed to uncover its recording mechanism and to optimize the recording performance. Visible light with short wavelength is always used as recording light in two-center scheme. But near-infrared recording light is of great interest to extend the practical applications of two-center holographic recording. In this dissertation, theoretical and experimental studies in these two spheres of two-center holographic recording are presented: (1) A numerical method based on PDECOL algorithm has been developed to rigorously solve photorefractive band transport equations. Combined with the solution of coupled-wave equations, the dynamic two wave coupling in photorefractive equations has been simulated under large light modulation and strong applied field. It is found that, under these conditions, the intensity coupling and phase coupling between two recording beams are both markedly enhanced. Energy and phase transfer occur simultaneously between the two coherent beams, and the phase of interference light pattern varies with the thickness of crystal. The grating pattern is not uniform any more, and bending hologram has been built. (2) Near-infrared nonvolatile hologram has been recorded, for the first time, by investigation of several kinds of doubly doped LiNbO3:Fe:X crystals with different deep center dopant. LiNbO3:Fe:Ni and LiNbO3:Fe:Rh have been found to have the best performance with recording light at wavelengths of 752.5nm and 799.3nm. The roles of shallow center Fe in near-infrared holographic recording has been studied by applications single color recording at 647.1nm, 752.5nm and 799.3nm. Because of the valley absorption of Fe in LiNbO3 crystal at about 1.6eV (760nm), LiNbO3:Fe、LiNbO3:Fe:Ni and LiNbO3:Fe:Rh all have the maximum and close saturation refractive index change. The intensity dependence of near-infrared two-center recording in LiNbO3:Fe:Ni and LiNbO3:Fe:Rh at 752.5nm and 799.3nm is found to be different with that of two-center scheme by recording at 633nm, and explanations have been given in terms of the decrease of photovoltaic coefficient of Fe in near-infrared, the increase of response time and the simultaneous erasure effect by sensitizing light during recording. (3) The characteristics and mechanism of two-center holographic recording in LiNbO3:Ce:Cu crystal have been studied theoretically and experimentally. The microphysical quantities of LiNbO3:Ce:Cu crystal are obtained from previous reports. Then numerical simulation has been applied by rigorous solution of two-center band transport equations. The effects of recording and sensitizing light, dopant compositions and the microphysical quantities on the two-center holographic recording performance in LiNbO3:Ce:Cu crystal have been investigated, and the numerical results are verified by experiments. Numerical simulation has been compared with the results obtained in LiNbO3:Fe:Mn crystal, and it comes to a conclusion that deep center Cu plays a key role in the holographic recording in LiNbO3:Ce:Cu crystal, and high diffraction efficiency and fixing efficiency have been achieved because of the strong space charge field built in Cu traps. (4) Red laser induced domain inversion in LiNbO3:Mg has been investigated at 647nm, and the reduction of nucleation field has been observed. The influence of inducing light intensity on the reduction has been studied and it has been found that the crystal surface chosen for illumination has effects on the reduction, which has not been found in previous report on laser induced domain inversion. From the experiments, reasonable assumption has been proposed. |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/15412]  |
| 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 | 李大汕. 双掺杂LiNbO3晶体近红外非挥发全息记录与优化[D]. 中国科学院上海光学精密机械研究所. 2007. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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