| 题名 | 双掺杂LiNbO<,3>晶体非挥发性全息存储的机理和优化研究 |
| 作者 | 刘德安 |
| 学位类别 | 博士 |
| 答辩日期 | 2000 |
| 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 铌酸锂晶体 全息存储 光色效应 漂白效应 |
| 其他题名 | Mechanism and Optimization of Nonvolatile Holographic Storage in Doubly Doped LiNbO3 Crystals |
| 中文摘要 | Buse等人于1998年在Nature杂志上提出并实现了LiNbO<,3>:Fe:Mn晶体非挥发性全息记录,该方案能实时和实地地固定光折变体全息,并实现了记录和固定的全光过程,在全息数据存储和局域体全息3-D光学集成等领域有潜在的应用前景.但该方案仍存在较低的衍射效率、较强的光致散射噪声和较小的记录灵敏度等实际应用问题,所以深入认识其记录机理,寻求更佳的记录方案和记录材料是使该固定方案实用化的重要任务.鉴于此,该论文对双掺杂LiNbO<,3>晶体非挥发性全息存储的机理和优化等问题进行了理论和实验研究. |
| 英文摘要 | Recently, Buse et al. have proposed an new technique to realize nonvolatile holographic storage in doubly doped LiNbO3:Fe:Mn crystals [Nature, Vol. 393, pp.665 (1998)]. This technique permits a real-time, in-situ and all-optical recording/fixing processing, and thus has the important potentials in the applications of optical memory and integrated 3-D optical system by local holograms. In practical application, there still remain the important problems, such as low fixed diffraction efficiency, strong light-induced scattering noise, small recording sensitivity, and so on. Therefore, it is a great task to investigate its mechanism further and explore optimal recording technique and recording material to improve its performance in practical applications. In this dissertation, the mechanism and the optimization of nonvolatile holographic recording in doubly doped LiNbO3 crystals are theoretically and experimentally investigated as the followings: (1) Through theoretical investigation on the nonvolatile holographic storage in photochromic LiNbO3:Fe:Mn, We have found self-enhancement effect caused by beam-coupling effect during both recording and optical fixing phases. Based on this self-diffraction effect, four kinds of recording and optical-fixing combinations (they are self-enhanced recording and self-enhanced fixing, self-enhanced recording and self-depleted fixing, self-depleted recording and self-enhanced fixing, self-depleted recording and self-depleted fixing) are proposed, and a steady-state analysis and a numerical simulation about the combinations are explored. The experimental results obtained by self-enhancement and self-depletion are consistent with the theoretical analysis. From the theoretical and experimental studies, it is seen that the highest diffraction efficiency available from the self-enhancement during both the recording and fixing phases may be twice as large as the lowest one from the self-depletion during both recording and fixing phases. It demonstrates that self-enhanced recording and self-enhanced fixing have to be considered and utilized in practical applications for nonvolatile holographic storage. To enhance the recorded photorefractive holograms and to suppress the scattering noise, a cyclic recording scheme by the repeat of a recording interval with a red pattern and an UV light and a followed post-exposure interval with UV light is proposed. The UV light used for the post-exposure not only excites more electrons into the shallower centers to lead to faster and stronger recording for the next recording cycle, but also acts as an additional incoherent illumination to erase the initially developed scattering noise gratings. Therefore, both an enhancement of diffraction efficiency up to 31% and a suppression of noise down to near zero are seen. At the same time, the recording period is also optimized. Finally, the self-enhancement is combined with this accumulative recording technique to further enhance diffraction efficiency. This technique can not only enhance diffraction efficiency but also suppress scattering noise, and no any additional equipment is needed. In principle, there are two kinds of dopants in the deeper center and the shallower center respectively. Thus, there are four possibilities for the doubly doping in lithium niobate crystals, i. e., LiNbO3:Fe:Mn, LiNbO3:Ce:Mn, LiNbO3:Ce:Cu and LiNbO3:Fe:Cu. In our previous experiments, we have observed the photochromic effect in LiNbO3:Fe:Mn and LiNbO3:Ce:Mn, and the no-sensitive effect in LiNbO3:Ce:Cu. Therefore, it is of significance to have a study on LiNbO3:Fe:Cu crystals and to finish a complete and comparable investigation on all the four possible lithium niobate crystals of the same double doping system. Fortunately, the bleaching effect, contrary to conventional photochromic effect, under an ultraviolet exposure is observed in LiNbO3:Fe:Cu crystals. Based on the bleaching effect, a three-step recording-transferring-fixing schemes are proposed to record nonvolatile holograms in such crystals. In the schemes two red laser beams and an ultraviolet illumination are used selectively to write the charge grating in the shallower centers, to develop the charge grating in the deeper centers by transferring the charge grating in shallower centers, and to fix out only the charge grating in deeper centers for unerasable read-out. Two other recording techniques are also explored for comparision. Experimental results show that the technique including recording phase by two interfering red beams, transferring phase by both UV light and a coherent red beam and fixing phase by a coherent red beam is optimal for novolatile recording by bleaching effect. As a result, two readout techniques under three effects are compared, and a comparison on the lithium niobate crystals of the same double doping system is outlined. The conclusion is that, among these four crystals, the performance of LiNbO3:Ce:Cu is optimal for nonvolatile recording. |
| 语种 | 中文 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/15436]  |
| 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 | 刘德安. 双掺杂LiNbO<,3>晶体非挥发性全息存储的机理和优化研究[D]. 中国科学院上海光学精密机械研究所. 2000. |
| 个性服务 |
| 查看访问统计 |
| 相关权益政策 |
| 暂无数据 |
| 收藏/分享 |
除非特别说明，本系统中所有内容都受版权保护，并保留所有权利。
修改评论