探索光致聚合物中的物理机制与化学动态效应-光学特性对全息技术的应用

Digital data are ubiquitous in modern life. The capabilities of current storage technologies are continually being challenged by applications as far ranging as the distribution of content, digital video, interactive multimedia, small personal data storage devices, archiving of valuable digital assets, and downloading over high-speed networks. Current optical data storage technologies, such as the compact disk (CD), digital versatile disk (DVD), and Blu-ray disk (BD), have been widely adopted because of the ability to provide random access to data, the availability of inexpensive removable media, and the ability to rapidly replicate content (video, for example)..Traditional optical storage technologies, including CD, DVD and BD, stream data one bit at a time, and record the data on the surface of the disk-shaped media. Alternative optical recording technologies, such as near field and super resolution methods, aim to increase density by creating still smaller data marks. Another approach that produces multiple layers is two-photon recording in homogeneous media. However, with all other optical technologies facing different obstacles to significant performance improvements,interest in holographic data storage (HDS) has dramatically increased in recent years. Holographic data storage (HDS) breaks through the density limitations of conventional storage technologies by going beyond two-dimensional layered approaches, to write data in three dimensions..The primary challenge throughout the history of holographic data storage (HDS) has been the development of a recording material that could enable the promise of this technology. The preliminary work in the different types of materials, especially in photopolymer materials, established a basic understanding of materials requirements. The dependence between the material performance (storage density, transfer rate, read-out fideity, environmental robustness, and lifetime) and characteristics (refractive index contrast, photosensitivity, dimentional stability, and optical quality), could be outlined. Optical characteristics of photopolymer satisfies holographic storage, which requires a material that can rapidly image the complex optical interference patterns generated during the writing step such that the imaged patterns are (1.) generated with adequately high contrast, (2.) preserved (both dimensionally and in their contrast) during subsequent, spatially co-located writing, (3.) are unchanged by read-out of the holograms, (4.) are robust to environmental effects, and (5.) survive over long periods (many years) of time. In order to further develop this type of material, the project carried out here will be focused on the quantitative and qualitative examination of photochemical kinetics and physical mechanisms that taking place during & post recordings. Consequently, it will not only build up a thorough theoretical understanding, but also provide significant contribution towards the material optimization.

纵观全息信息存储（HDS）技术的历史,现今首要的挑战便是开发和探索全息记录的材料,从而成为这项技术可行的承诺。而在众多记录材料中,光致聚合物迅速成为领先的候选材料并已经受到越来越多的关注,他们表现出了低损耗,高对比度的折射率模式等记录特性。然而，许多关键性的问题仍有待解决(如存储密度,环境的稳定性和寿命,和材料的折射对比率,尺寸稳定性,光学质量等等之间的依赖关系)，则形成了对材料内部结构和机理深度研究的必须要求。本项目以独特的从宏观切入微观的路线,即运用全息光学技术结合高分子化学材料的分析方法,对光致聚合物中所产生光化学动态效应和物理机制获得更深入的学习和以及未知领域的探究。而材料在记录全息图样过程中所产生的,以及其本身光学特性所涉及的问题将结合更完善更新颖的理论模型来管理。目的是为了充分地优化材料的组成和极大地挖掘其潜在的性能,与此同时形成一个更物理化更彻底和更高效的理论体系和模型结构。

光致聚合物材料于1969年首次被Close et. al 提出并用于全息光栅记录，纵观全息信息应用技术的发展史, 光致聚合物迅速成为领先的候选材料,他们表现出了低损耗，高对比度的折射率模式等记录特性，且制备过程相对简便。光致聚合物潜在多样的特性，使其在信息存储，三维显示，混合光电子，太阳能聚合物(电池)，嵌入式光波导以及衍射光学元器件领域均备受关注。然而，在众多记录材料中只有极小部分成为商业应用的可能，但却仍然存在着各方面需要克服的关键性问题(不足与限制)，更加凸显出开发和探索全息记录材料的重要性，从而成为这项技术可行的承诺。该项目从宏观切入微观的路线，即应用全息光学法则结合高分子化学材料的分析方法，在工作中我们发现想要进一步发展和优化该类记录材料的应用性能，一个对光致聚合物中所产生光化学动态效应和物理机制更深入更彻底的探究理解已经成为迫切和必需。..在该工作中，我们重点学习和探索了在全息双光源曝光条件下光致聚合物材料所表现出来的诸多特性，并加以整合：（1.）多重光敏剂的多重吸收，透射，散射，复合以及漂泊的机制，从而发现不同的自由基R•的效率和产量；（2.）不同材料系统的由于尺寸稳定性所决定的不同的光学厚度；（3.）更周全深入的材料折射指数性能对曝光强度和记录空间频率响应的不同表现，从而获得了对于材料在不同的条件下呈现出额外新特性的认知，尤其是获得了在极端的情况下对折射性能衰变的解释（聚合，扩散和终止之间的相互牵制与影响）；（4.）材料收缩膨胀性能的影响因素及比较研究，并发现关键问题所在；（5.） 混合型材料的复式叠加记录光栅下所带来的特殊的属性，并比较了它与单光栅强度增长的异同以及其潜在的应用可能性；（6.）拓展了更完善，更物化更普适的“多重多维-扩散-反应”的理论体系和模型结构来管理相关有效进程，并对材料特性所带来的影响和优化方向给予合理地预判和分析，使其成为一个高效的工具。 更重要的是，这项工作不仅使我们获得深层次的认知，而且对将来光致聚合物材料方面的研究工作奠定了基石并指明了方向。