【作者】 袁（韦华）；

【导师】 陶世荃；

【作者基本信息】 北京工业大学 ， 光学， 2003， 硕士

【摘要】 体全息存储是一种高速并行读取的信息存储技术，在海量信息存储、光学相关图像库的建立、光学滤波器等方面取得了较大的进展。体全息存储的首选记录材料是光折变晶体（如Fe:LiNbO₃），但直接存储在晶体中的信息容易受光和热的影响而丢失。克服晶体中光栅在暗保存和光读出过程中容易衰减的弱点，可使体全息存储成为一种具有实用性的非易失性存储技术。热固定是解决这一问题的有效方法之一。热固定包括定影和显影两个过程。定影是通过加热记录了体全息光栅的晶体使晶体中的离子运动并去补偿记录信息的电子光栅，形成与电子光栅互补的离子光栅；显影是在室温下用均匀光束照射晶体以擦除掉电子光栅，得到离子光栅。在以后的暗保存或者光读出状态，这种离子光栅能较长久地保持稳定，实现非易失性存储。 小型实用的高密度全息存储热固定系统以实用性为目的，主要针对热固定方法中的记录后补偿方式（即室温记录，高温定影，再室温显影），从两个方面开展研究设计。一方面，以全息理论和Yariv热固定的带输运模型为指导，调研晶体材料的全息特性和热固定特性，在大量实验的基础上遴选出既适合大规模全息存储又有优良热固定性能的晶体；同时提出快速热固定流程，过程稳定，重复性好，缩短热固定时间。另一方面，围绕高密度全息存储设计复用存储技术，制作了有较大存储能力的小型实用热固定全息系统，包括角度一维度复用系统、离线加热的晶体夹持器和复位装置、适合离线与在线加热的温控加热装置。对于边长为1cm的立方晶体，复用系统在水平方向和垂直方向上的选择角分别为0.008°和0.41°，能够存储10000幅数据页；复位装置的角度复位精度优于0.001°；温控加热装置的控温精度为0.1℃。最后，采用分批热固定方法在Fe:LiNbO₃中存储1000幅二值数据页，全部读出所有的图像，衍射效率均匀，图像质量良好。存储系统的暗保存、光擦除时间常数分别为5.4年和43.6小时。本系统的研制成功有利于全息存储热固定的实用化。更多还原

【Abstract】 Holographic data storage is a subject of considerable current and commercial interest. Volume holographic storage (VHS) has attracted interest because of its potential in high-density and fast parallel readout. Photorefractive crystals (e.g., doped LiNbO3) have been considered as one kind of the most important materials for VHS owing to wider dynamic range and their commercial availability in large size. However, the volume holographic gratings in photorefractive crystals are liable to dark decay and erasure under readout illumination. Thermal fixing method is a feasible solution to this problem. A complete thermal fixing procedure includes two steps i.e., fixing and developing. In fixing stage, the ions in crystals move to form an ionic grating that compensates the electronic grating at elevated temperature. In developing stage after cooling crystals to room temperature, a homogeneous illumination erases the electronic grating and brings out the ionic grating. The ionic grating has a longer lifetime both in dark and under readout illumination, so nonvolatile storage comes true.This thesis is aimed at building up a compact high-density holographic storage system with thermal fixing function to make the nonvolatile storage technology practical. This system uses mainly post-recording fixing technique that involves recording at room temperature, fixing at elevated temperature, and developing at room temperature. The work of this thesis is divided into two parts. Firstly, based on holographic principles and the band transport atom theory for thermal fixing, given by Yariv, we investigated holographic characteristics and thermal-fixing characteristics of photorefractive crystals. Upon a lot of experiments, a practical assessment method is worked out for selection of crystals that are suitable for large-scale VHS and shows good thermal-fixing performance as well. Meanwhile, a method for rapid thermal fixing is presented, which has some advantages over conventional technique in stability and repeatability, while shortened the fixing time. Secondly, we have designed and made a compact practical holographic system that consists of angular-fractal multiplexing system and thermal fixingequipment, including a crystal repositioner with precision less than 0.001 . For a cubic crystal of 1cm 1cm 1cm, the horizontal and vertical selective angles are 0.008 and 0.41 respectively. So the system is capable of storing 10000 holograms. We also have made an off-line heater and an on-line heater, both of which are controlled by a temperature controller (model EUROTHERM). The temperature controller can control temperature variation less than 0.1 in the chamber of the heater.We stored 1000 binary pages in a 0.03% FerLiNbO3 crystal using this system and batch thermal fixing technique. All the stored images are retrieved, and the retrieved images have uniform diffraction efficiency and good quality. Experiments show that the holograms fixed in this crystal may last 5.4 years in dark and 43.6h under readout illumination. We believe that the successful building up of this system will make a great progress in high-density nonvolatile volume holographic storage.更多还原