波导多层光存储器件的研制及其散射模型

【作者】 杨涛；

【导师】 梁忠诚；

【作者基本信息】 南京师范大学 ， 物理电子学， 2004， 硕士

【摘要】 光学数据存储技术如CD和DVD光盘已在音像视听和计算机数据存储领域得到广泛的应用。目前人们正在设法进一步提高光盘存储器的存储密度，如采用大数值孔径物镜或使用较短波长光源(如蓝光、紫光存储)。但是，现今的光盘存储面密度已经接近由电磁波衍射效应引起的空间分辨率极限，下一代超高密度光存储器将建立在突破衍射分辨率极限的近场光学存储技术(如采用固体浸没透镜的方法)或突破光盘平面限制的三维光学体存储技术之上。 本文就介绍一种新型的三维光存储方法——波导多层存储。它的原理是：利用波导缺陷记录数据、利用波导缺陷的漏光效应读出数据和利用波导对光的空问约束作用实现层选址。这种方法的可行性已被文中十层波导原理性实验成功证实。 为了能够制造出实用的波导多层存储系统，文中对可适用于本存储系统的多种数据读写方法从原理上作了概述。其中，“直写法”的数据记录方式和“散射型”的数据读出方式最具实用性。通过对导波光学原理以及光散射理论的研究，我们得出了波导表面散射光强的指数衰减规律。考虑到某些探测器要求整个波导表面散射光强均匀不变，我们又推导出了这种情况下的衰减系数随着光传播方向变化规律公式。此外，我们还运用转移矩阵的方法对衰减系数的相关参量进行了分析。这些工作进一步了完善波导散射理论。 在以上理论推导的基础上，我们设计了波导表面光散射的实验。该实验不仅证实了散射光强的指数衰减规律，而且分别得出了不同波导样品的衰减系数大小。此外，实验结果还反映了当仅仅改变其中一个参量(如信息符的深度或密度)时，衰减系数的变化趋势。这为今后进一步提高器件性能提供了依据。 本文还对其它高密度光存储的原理作了介绍。通过与其它光存储方法的比较，可以预计：波导多层技术有希望成为新一代高密度光存储领域中的有力竞争者。更多还原

【Abstract】 Optical memory such as compact disks (CD) and digital versatile disks (DVD) are becoming essential as audio and visual storage media as well as external computer data storage media. Many efforts have been made to increase the memory density of the optical disks such as increasing the numerical aperture of the objective lens and decreasing the light wavelength to blue or purple range. However, the present optical disk memory density has almost reached its upper limitation resulted from the diffraction of electromagnetic wave and the nature of two-dimensional storage mode. Consequently, current endeavors to surpass this limitation are made in two main directions. The one way is to use the near field optics techniques such as employing the solid immersion lens and the aperture system. The other way is to extend the data recording from two-dimension (2D) surface to three-dimension (3D) volume.In this paper, we introduce a novel 3D optical storage method-multilayered waveguides storage (MWS). The principles of MWS are: recording the data in the form of the waveguide defective points for information writing, collecting the radiation scattered from the waveguide defects for date reading and restricting the light within the waveguide layer for layer addressing. All of these have been proved to be feasible by the successful experimental results with 10 layers device demonstrated in this paper.In order to fabricate a real storage system, a variety of usable date writing and reading methods are outlined theoretically in this paper. Among them, "Direct Writing Method" and "Scattering Method" is practical particularly. After studying the waveguide principles and the optical scattering theories, we reach an exponential decay rule of waveguide surface scattering light intensity. Taking into account the condition that scattering light intensity of the whole waveguide is uniform, which meets the requirement of some detectors, we deduce a formula about the relation between variable decay coefficient and conductive light passing distance. Furthermore, the corresponding parameters of the decay coefficient are analyzed through applying the transfer matrix theory. All these efforts contribute to the perfection of the waveguide scattering theory.On the basis of the theories above, an experiment about light scattering on waveguide surface is designed, which not only verifies the correctness of the exponential decay rule of scattering light intensity, but also gives the exact decay coefficients of varied waveguide samples respectively. Moreover, the experiment results reflect the trends of the decay coefficient when only changing one of its parameters such as depth or density of the information pits. The success of this experiment makes good preparation for the optimization of MWS device performance.In addition, other high density optical storage methods are introduced in this paper. By comparing the advantages of WMS with which of other methods, we can easily and confidently draw the conclusion: MWS will be the prevalent force influencing the main stream of optical storage in the future.更多还原